the physics of situps
RichD
a weekend of sadomasochism, conducted
annually by my college karate club, called
'special training'. One part of this consisted
of a ton of situps.
We paired off, with locked legs, done by count.
It was impossible to do them all with good form,
so I came up with a trick: throw my arms forward
as hard as I could, on each one, to raise myself.
But Newton's physics tells us an isolated body
cannot generate net momentum; action = reaction.
But I swear I couldn't have completed that segment
without the arm swing. So the question is, did this
trick really work as a cheat, physically? Or was
it just an illusion?
--
Rich
hal
Nah, it makes perfectly good sense. You are adding another set of
muscle groups to the movement: by using your forearm muscles to pull
you arms forward you accelerate the mass of your arms forward which in
turn is transferred to your upper body to assist in the lift. Makes
sense when you think of the muscle groups you are using for the
movement.
>--
>Rich
Ray Vickson
> Long ago, in my wasted youth, I participated in
> a weekend of sadomasochism, conducted
> annually by my college karate club, called
> 'special training'. One part of this consisted
> of a ton of situps.
>
> We paired off, with locked legs, done by count.
> It was impossible to do them all with good form,
> so I came up with a trick: throw my arms forward
> as hard as I could, on each one, to raise myself.
>
> But Newton's physics tells us an isolated body
> cannot generate net momentum; action = reaction.
But, you are not an isolated body: you are lying on the floor, and so
you can get momentum transfer between yourself and the Earth. When you
swing your arms forward you are converting some internal energy into
kinetic energy (and momentum) of the hands/arms, and this momentum
helps you to raise your torso.
Similar question: how the heck can a child sitting on a stationary
playground swing eventually pump herself up to a wide arc of swing,
sometimes almost high enough to loop-the-loop, and all without
touching her feet to the ground?
R.G. Vickson
SPORTfighter
to get your arms moving forward u are using muscles other than your
abs.
once they are moving forward the weight of them going forward reduces
the amount of ab work u need.
so though you expend equal energy to get up ther, you are depending
less on the more taxed muscle group, the abs.
i do a straight hour of abs wednesday at noon.
its divided into mostly 5 minute rounds with a 30 second break.
they consist of decline abs for a minute holding a 45 pound plate,
onto the roller thingee, onto im hanging from a chinup bar and pull my
knees up to the bar, onto twists with a heavy dumbbell while sitting
on my ass feet in the air.
anyways enough bragging.
but as the rounds ad up i subconsvciously and sometimes consciously
find ways to limit the amount the abs are focred to do, all exerzises
are diferent and ther are many ways to cheat in each.so im very aware
of that tyhough to are still using perhapos equal strength to get it
doen, one round using the top abs more, and the next the lower abs
more really helps you deal.
cant speak for the pysics, or even spell it.but this shits cpommon
sesne rehardless of what newton or einstein says about it.
those guys are dumb as shit anyways.
TimR
>
> But Newton's physics tells us an isolated body
> cannot generate net momentum; action = reaction.
>
> --
> Rich
You didn't generate net momentum.
Your arms moving one direction cancel the momentum of the body moving
the other direction. Your arms are low mass but move quickly, your
body is higher mass but moves slowly. Net momentum from the arms was
zero. But the forces from the arms were just enough to add to what
your abs were doing.
Wannabe
Your belly muscles are pulling your torso up with your ass as the
fulcrum. By throwing your arms forward, you reduce the "moment = the
sum of (mass * distance perpendicular to the gravitational force)"
contributed by the mass of your arms, where the perpendicular distance
is just the horizontal distance when you are lying flat on the floor.
Likewise, you will make it harder for the belly muscles to pull your
torso up if you extend your arms horizontally above your head because
you increase the "moment" contribulted by the mass of your arms that
your belly muscles have to work agains.
http://en.wikipedia.org/wiki/Moment_(physics)
Wannabe
=======
RichD
> > But Newton's physics tells us an isolated body
> > cannot generate net momentum; action = reaction.
> You didn't generate net momentum.
>
> Your arms moving one direction cancel the momentum
> of the body moving the other direction. Your arms are low
> mass but move quickly, your body is higher mass but
> moves slowly. Net momentum from the arms was
> zero. But the forces from the arms were just enough to add to what
> your abs were doing.
Speed of the different parts doesn't matter.
Momentum is conserved.
If an astronaut is floating in outer space,
can he fly by flapping his arms?
--
Rich
Sam Wormley
Are you taking into account the differences in
static and kinetic friction?
RichD
> >One part of this consisted
> >of a ton of situps.
>
> >We paired off, with locked legs, done by count.
> >It was impossible to do them all with good form,
> >so I came up with a trick: throw my arms forward
> >as hard as I could, on each one, to raise myself.
>
> >But Newton's physics tells us an isolated body
> >cannot generate net momentum; action = reaction.
> >But I swear I couldn't have completed that segment
> >without the arm swing. So the question is, did this
> >trick really work as a cheat, physically? Or was
> >it just an illusion?
>
> Nah, it makes perfectly good sense. You are adding another
> set of muscle groups to the movement: by using your
> forearm muscles to pull you arms forward you accelerate
> the mass of your arms forward which in
> turn is transferred to your upper body to assist in the lift.
No, that's the naive "arms pull you forward"
explanation, which fails; the boostrap fallacy.
Throwing the arms forward pushes backward
against the shoulders. It doesn't create net motion.
If you reach down and grab your shoelaces,
can you pull yourself to the ceiling?
I wonder if there's some other action occurring,
which does assist in the situp...
--
Rich
RichD
> > One part of this consisted of a ton of situps.
>
> > We paired off, with locked legs, done by count.
> > It was impossible to do them all with good form,
> > so I came up with a trick: throw my arms forward
> > as hard as I could, on each one, to raise myself.
>
> > But Newton's physics tells us an isolated body
> > cannot generate net momentum; action = reaction.
> > But I swear I couldn't have completed that segment
> > without the arm swing. So the question is, did this
> > trick really work as a cheat, physically? Or was
> > it just an illusion?
>
> static and kinetic friction?
No. How would that explain it? The tailbone is the
only point in contact with the floor.
--
Rich
hal
<r_dela...@yahoo.com> wrote:
>On Nov 13, hal wrote:
>> >One part of this consisted
>> >of a ton of situps.
>>
>> >We paired off, with locked legs, done by count.
>> >It was impossible to do them all with good form,
>> >so I came up with a trick: =A0throw my arms forward
>> >as hard as I could, on each one, to raise myself.
>>
>> >But Newton's physics tells us an isolated body
>> >cannot generate net momentum; =A0action =3D reaction.
>> >But I swear I couldn't have completed that segment
>> >without the arm swing. =A0So the question is, did this
>> >trick really work as a cheat, physically? =A0Or was
>> >it just an illusion?
>>
>> Nah, it makes perfectly good sense. =A0You are adding another
>> set of muscle groups to the movement: =A0by using your
>> forearm muscles to pull you arms forward you accelerate
>> the mass of your arms forward which in
>> turn is transferred to your upper body to assist in the lift. =A0
>
>No, that's the naive "arms pull you forward"
>explanation, which fails; the boostrap fallacy.
>Throwing the arms forward pushes backward
>against the shoulders.
No it doesn't. You admitted it's easier to sit up that way. That
proves theres a net force pulling your body towards your feet.
> It doesn't create net motion.
It causes momentum in your arms which is transferred to your
shoulders.
>
>If you reach down and grab your shoelaces,
>can you pull yourself to the ceiling?
Absurd. You have nothing available to overcome the force of gravity.
>
>I wonder if there's some other action occurring,
>which does assist in the situp...
No, the action is kinetic energy build up in your arms by swinging
them. Like a flail, when the swinging end reaches it's limit of
travel the kinetic energy is transfer to the fulcrum and to the base
piece of the weapon. The energy in your arms is transferred to your
upper body through your shoulders and pulls your upper body up and
towards your feet.
>
>--
>Rich
RichD
> > One part of this consisted of a ton of situps.
>
> > We paired off, with locked legs, done by count.
> > It was impossible to do them all with good form,
> > so I came up with a trick: throw my arms forward
> > as hard as I could, on each one, to raise myself.
>
> > But Newton's physics tells us an isolated body
> > cannot generate net momentum; action = reaction.
>
> But, you are not an isolated body: you are lying on the floor,
> and so you can get momentum transfer between yourself
> and the Earth.
Mabe...
> When you swing your arms forward you are converting
> some internal energy into kinetic energy (and momentum)
> of the hands/arms, and this momentum
> helps you to raise your torso.
The arms connect at the shoulder joint,
they do not push off the ground. So I do
not find this explanation satisfactory.
> Similar question: how the heck can a child sitting on a stationary
> playground swing eventually pump herself up to a wide arc of swing,
> sometimes almost high enough to loop-the-loop, and all without
> touching her feet to the ground?
You read my mind! I was thinking the same thing...
Swinging the legs back and forth certainly produces
energy, but how is it directed? At the bottom, feet
forward: forward momentum, feet back: bacward momentum.
But again, the body is an isolated system, how does this
generate net momentum?
At my next seance, I will summon old Isaac, and
present this chestnut to him...
--
Rich
Greendistantstar
What...no chi?
GDS
"Let's roll!"
Sam Wormley
Slides easier when lifted. Also it takes more force to
"break" static friction.
Wannabe
news:WZednXpIC_9B4WLX...@westnet.com.au...
>>
>> http://en.wikipedia.org/wiki/Moment_(physics)
>>
>>
>> Wannabe
>> =======
>
> What...no chi?
>
> GDS
>
> "Let's roll!"
The gravitational force is the chi in this discussion.
By the way, I think I have learned enough BJJ basics so that I can
benefit
from watching BJJ training videos. I now have got some from Renzo
Gracie.
Can you please give me some good names in BJJ so I will see if I can
scrounge from the internet?
RichD
> >> >One part of this consisted
> >> >of a ton of situps.
>
> >> >We paired off, with locked legs, done by count.
> >> >It was impossible to do them all with good form,
> >> >as hard as I could, on each one, to raise myself.
>
> >> >But Newton's physics tells us an isolated body
> >> >But I swear I couldn't have completed that segment
> >> >trick really work as a cheat, physically? Or was
> >> >it just an illusion?
>
> >> Nah, it makes perfectly good sense. You are adding another
> >> set of muscle groups to the movement: by using your
> >> forearm muscles to pull you arms forward you accelerate
> >> the mass of your arms forward which in
> >> turn is transferred to your upper body to assist in the lift.
>
> >explanation, which fails; the boostrap fallacy.
> >Throwing the arms forward pushes backward
> >against the shoulders.
>
> No it doesn't. You admitted it's easier to sit up that way.
> That proves theres a net force pulling your body towards
> your feet.
um, it doesn't PROVE anything... I said it
FEELS easier, when throwing the arms.
That's the point of the question.
You think all your subjective perceptions
correspond to objective reality?
> > It doesn't create net motion.
>
> It causes momentum in your arms which is transferred
> to your shoulders.
Could be... did they revoke Newton's 3rd,
since my school days?
> >If you reach down and grab your shoelaces,
> >can you pull yourself to the ceiling?
>
> Absurd. You have nothing available to overcome the
> force of gravity.
Sure you do - your arm strength. If you pull
up on your shoes really hard, that opposes
gravity, doesn't it? Just like lifting any other
weight...
> >I wonder if there's some other action occurring,
> >which does assist in the situp...
>
> No, the action is kinetic energy build up in your arms by swinging
> them. Like a flail, when the swinging end reaches it's limit of
> travel the kinetic energy is transfer to the fulcrum and to the base
> piece of the weapon. The energy in your arms is transferred to your
> upper body through your shoulders and pulls your upper body up and
> towards your feet.
Let's say an astronaut is floating 20 feet
from the ship, and his jets are dead. You
believe he can throw his arms forward, repeatedly,
generate kinetic energy, and pull himself home?
Wait a sec, let me get some popcorn...
--
Rich
wallen
> > It causes momentum in your arms which is transferred
> > to your shoulders.
>
> Could be... did they revoke Newton's 3rd,
> since my school days?
Its all about the muscles moving in sync. the first movement will be
the arms. since you are not floating in space whatever force it
creates can be transfered to an object you can push away from-in this
case the floor.
if you will move only the arms, the shoulder will be the fulcrum and
you will achieve , well nothing. but since right after the arm flail,
you crunch your abs, the fulcrum then becomes your butt. so whatever
force your arm created will be added to the force created by your abs.
Its more like a rolling/wave motion, instead of lifting your whole
body. since rolling is more efficient than lifting, so you can do more
crunches. But as a caveat, this do not create the same amount of
stress to your abs, so in the long run, its less efficient as strenght
exercise, but more of an aerobic one.
> Sure you do - your arm strength. If you pull
> up on your shoes really hard, that opposes
> gravity, doesn't it? Just like lifting any other
> weight...
dont make a fool of yourself. you know that is a stupid conclusion. It
wont work as when you do this,you are not creating any force against
gravity to lift yourself. you are only stretching the laces. even when
lifting other objects, you dont float, you only support the obect your
lifting.
> Let's say an astronaut is floating 20 feet
> from the ship, and his jets are dead. You
> believe he can throw his arms forward, repeatedly,
> generate kinetic energy, and pull himself home?
Again a stupid remark. you know this to be an impossibility, as there
is nothing to push against from.
he can however with a piece light strong rope tie a small weight on
one end swing it around and at the right moment release it. this will
throw the weight and the string towards the ship where another
astronaut can capture it and pull him in. the throw will make him move
the other direction, but since his mass is many times greater than the
string and weight, the string will go further and faster away.
PD
When you throw your arms forward, your shoulders are still in contact
with the ground. Because your shoulders push down on the ground, the
ground pushes up on the shoulders, exerting a torque on your torso
with your hips as the pivot point.
Another way of saying the same thing is that swinging your arms
forward gives your body as a whole angular momentum. (Again, your
shoulders touching the ground makes your body not isolated and so the
angular momentum of your torso will not remain zero.) When your arms
stop swinging forward relative to your torso, the angular momentum is
passed to the torso and up you go. (Similar to the way your car noses
forward when you apply the brakes to stop the wheels' movement
relative to the chassis.)
PD
Daniel
by changing the body's position the centre of gravity is altered. try
this very slowly on the swing and you will see the position the swing
hangs is slightly altered. by changing the c.o.g the other way the
reverse is noted. NOW...and this is the clever part...if you do this
at ..and only at...or at least very very close to...the resonant
frequency of the system (in this case the swing)... where the the
mechanical impedance to the stimulas (i.e the actions of the
'swinger') is the lowest...you will generate a large response. if you
do it at any other frequency (other than subharmonics i.e half or
quarter frequencies) the movement generated will be very small. hope
this helps with ur ab development :)
Daniel
RichD
> > > how the heck can a child sitting on a stationary
> > >playground swing eventually pump herself up to a wide
> > >arc of swing, and all without touching her feet to the ground?
>
> > I was thinking the same thing...
>
> > Swinging the legs back and forth certainly produces
> > energy, but how is it directed? At the bottom, feet
> > forward: forward momentum, feet back: bacward momentum.
> > But again, the body is an isolated system, how does this
> > generate net momentum?
>
> by changing the body's position the centre of gravity is
> altered. try this very slowly on the swing and you will see
> the position the swing hangs is slightly altered. by changing
> the c.o.g the other way the reverse is noted.
By altering one's shape, the c.o.g. appears to
shift, relative to the body, but in absolute space
(the swing's reference frame), the c.o.g. is fixed;
Newton's 3rd, remember? An isolated body
cannot translate its center.
> if you do this at .the resonant frequency
> of the system (in this case the swing)... where the the
> mechanical impedance to the stimulas (i.e the actions of the
> 'swinger') is the lowest...you will generate a large response.
> if you do it at any other frequency the movement generated
> will be very small.
I don't think so...
A pendulum can overcome its frictional losses,
through an external kick - e.g. a clock - but in
the swing case, the 'kick' is generated internally;
the child is part of the system. I don't believe a
pendulum can swing indefinitely through an
internal mechanism - the kick must come from outside.
However, I think you're on the right track - the key
is the grip, on the ropes. As the legs kick forward,
the hands pull back, creating a couple, and a
torque, which pulls the seat. I am not quite sure
this explains it, though, as we'd have to consider
the reaction on the swing frame, to see if it makes
sense.
--
Rich
YumYumPandaburger
> If you reach down and grab your shoelaces,
> can you pull yourself to the ceiling?
***HEAD EXPLODES***
Daniel
> On Nov 19, Daniel <nidan.da...@gmail.com> wrote:
>
>
>
>
>
> > > > how the heck can a child sitting on a stationary
> > > >playground swing eventually pump herself up to a wide
> > > >arc of swing, and all without touching her feet to the ground?
>
> > > I was thinking the same thing...
>
> > > Swinging the legs back and forth certainly produces
> > > energy, but how is it directed? At the bottom, feet
> > > forward: forward momentum, feet back: bacward momentum.
> > > But again, the body is an isolated system, how does this
> > > generate net momentum?
>
> > by changing the body's position the centre of gravity is
> > altered. try this very slowly on the swing and you will see
> > the position the swing hangs is slightly altered. by changing
> > the c.o.g the other way the reverse is noted.
>
> By altering one's shape, the c.o.g. appears to
> shift, relative to the body, but in absolute space
> (the swing's reference frame), the c.o.g. is fixed;
> Newton's 3rd, remember? An isolated body
> cannot translate its center.
just imagine for a second that you stand on a swing upright whilst the
swing is at rest (arms are going to be bent at the elbows). THEN you
push your arms out sraight in front of you which pushes the top of
your body backwards, you will see that the angle of the rope has
changed relative to swing frame of reference. Now if you reverse this
process and pull on the rope and push yourself forwards the rope will
hang a few degrees the OTHER way now. If you do this slowly and
repetetivly nothing much will happen BECOS the frequency is way off
resonance. BUT if you time your pushes and pulls to be at the resonant
freq or submultiple of it...then the oscillations (or swings) will
increase in magnitude and we all know the results...very high swings.
To alter the angle of the swing requires energy to overcome the
friction at the top of the swing...this is the mechanical damping of
the system. Jumping on a trampoline is similar...try jumping at a
different frequency to the natural resonance of the system and you
won;t get very far...find the right rate to jump and you will get
higher and higher. Another mechanism of imparting energy to the system
is due to the fact that in the normal bodily movement of kicking out
and leaning back...and then feet down and pull forward one is actually
changing one's centre of mass higher and lower against gravity...this
results in the required swing bt again only if done at the right freq.
see http://www.phy.cuhk.edu.hk/phyworld/articles/swing/swing_e.html
for more details
Daniel
> > if you do this at .the resonant frequency
> > of the system (in this case the swing)... where the the
> > mechanical impedance to the stimulas (i.e the actions of the
> > 'swinger') is the lowest...you will generate a large response.
> > if you do it at any other frequency the movement generated
> > will be very small.
>
> I don't think so...
>
> A pendulum can overcome its frictional losses,
> through an external kick - e.g. a clock - but in
> the swing case, the 'kick' is generated internally;
> the child is part of the system. I don't believe a
> pendulum can swing indefinitely through an
> internal mechanism - the kick must come from outside.
>
> However, I think you're on the right track - the key
> is the grip, on the ropes. As the legs kick forward,
> the hands pull back, creating a couple, and a
> torque, which pulls the seat. I am not quite sure
> this explains it, though, as we'd have to consider
> the reaction on the swing frame, to see if it makes
> sense.
>
> --
> Rich- Hide quoted text -
>
> - Show quoted text -
RichD
> > > > > how the heck can a child sitting on a stationary
> > > > >playground swing eventually pump herself up to a wide
> > > > >arc of swing, and all without touching her feet to the ground?
>
> > > > energy, but how is it directed? At the bottom, feet
> > > > forward: forward momentum, feet back: bacward momentum.
> > > > But again, the body is an isolated system, how does this
> > > > generate net momentum?
>
> > > by changing the body's position the centre of gravity is
> > > altered. try this very slowly on the swing and you will see
> > > the position the swing hangs is slightly altered. by changing
> > > the c.o.g the other way the reverse is noted.
>
> > By altering one's shape, the c.o.g. appears to
> > shift, relative to the body, but in absolute space
> > (the swing's reference frame), the c.o.g. is fixed;
> > Newton's 3rd, remember? An isolated body
> > cannot translate its center.
>
> just imagine for a second that you stand on a swing upright whilst the
> swing is at rest (arms are going to be bent at the elbows). THEN you
> push your arms out sraight in front of you which pushes the top of
> your body backwards,
I got a chance to try this - standing on the swing,
then thrusting my arms. I ended up almost horizontal,
seat swinging forward. And similar effect sitting,
extending my legs.
However, it is not at all clear that this generated
a net torque on the swing, as you claim. Merely
shifting one's shape doesn't warrant such a conclusion.
> you will see that the angle of the rope has
> changed relative to swing frame of reference. Now if you reverse this
> process and pull on the rope and push yourself forwards the rope will
> hang a few degrees the OTHER way now.
Really? You mean, the seat support chains no
longer hang like a plumb line, aimed at the earth's
center? You might want to publish this discovery,
in a more prestigious journal than Usenet...
> If you do this slowly and repetetivly nothing much will happen
> BECOS the frequency is way off resonance. BUT if you
> time your pushes and pulls to be at the resonant
> freq or submultiple of it...then the oscillations (or swings) will
> increase in magnitude
We know the leg swing imparts kinetic energy somehow,
but your explanation is not convincing.
> Another mechanism of imparting energy to the system
> is due to the fact that in the normal bodily movement of kicking out
> and leaning back...and then feet down and pull forward one is actually
> changing one's centre of mass higher and lower against gravity...this
> results in the required swing bt again only if done at the right freq.
Kicking out and flattening does lower the body's c.o.g;
but the support joints above, on the swing frame, do
not see any extra weight. I don't see how this produces
net momentum.
Imagine you place a rectangular box on the swing,
which can 'pancake' itself at the nadir of each swing,
lowering its c.o.g. Would that kick the swing higher?
> http://www.phy.cuhk.edu.hk/phyworld/articles/swing/swing_e.html
That pseudo-explanation is a bowl of mush; text
does not correspond to diagram, the child doesn't
raise and lower himself as described. It actually
weakens your argument.
But wait.... you found it with Google... and GOOGLE
IS YOUR FRIEND... she never lies to you... IT MUST BE TRUE.....
Daniel
> longer hang like a plumb line, aimed at the earth's
> center? You might want to publish this discovery,
> in a more prestigious journal than Usenet...
Sarcasm is inappropriate when someone is doing his best to explain
something to you, even if they are wrong. Obviously respect for people
trying to help you is something that you have not learned from the
MAs...which you should have done.
Take a rigid steel bar with a hook at 1 end. Hang it from a point
above using the hook. Measure angle relative to a normal from the
Earth's surface. It will be 0 degrees. Now, at the bottom of the bar
fix another bar at right angles to the hanging bar. Measure angle
deviation of hanging bar to what it was before. 0 degrees? I doubt it.
Regarding publications: suffice to say I have published...in something
more prestigous than Usenet.
If you desire to continue this discussion I am happy to...as i find it
interesting and possibly mutually informative...however a masochist I
am not..and if you continue your sarcastic put-downs then I see no
need to continue this discussion.
Daniel
purple
>> Really? You mean, the seat support chains no
>> longer hang like a plumb line, aimed at the earth's
>> center? You might want to publish this discovery,
>> in a more prestigious journal than Usenet...
>
> Sarcasm is inappropriate when someone is doing his best to explain
> something to you, even if they are wrong.
But it feels soooooooo good!
> Obviously respect for people
> trying to help you is something that you have not learned from the
> MAs...which you should have done.
> Take a rigid steel bar with a hook at 1 end. Hang it from a point
> above using the hook. Measure angle relative to a normal from the
> Earth's surface. It will be 0 degrees.
This is quite muddy as statements go. Measure the angle of
what? The bar? It hangs plumb, pointing to the center of
the earth if the system was properly balanced and measured.
> Now, at the bottom of the bar
> fix another bar at right angles to the hanging bar. Measure angle
> deviation of hanging bar to what it was before. 0 degrees? I doubt it.
That all depends on whether or not the attached new bar is
hung in a balanced fashion. You have inadequately defined
the problem so the outcome is uncertain. I am unimpressed
by this discussion thus far.
> Regarding publications: suffice to say I have published...in something
> more prestigous than Usenet.
For the purposes of this discussion, who cares where you've
published? If you wrote as badly as you've written here I
wouldn't brag about my text appearing in a "prestigous"
publication.
> If you desire to continue this discussion I am happy to...as i find it
> interesting and possibly mutually informative
It may be, if you drop sci.physics and rec.org.mensa from
the distribution.
...however a masochist I
> am not..and if you continue your sarcastic put-downs then I see no
> need to continue this discussion.
Scary!
> Daniel
Fraser Johnston
"Daniel" <nidan...@gmail.com> wrote in message
news:a387670b-dc11-43ae...@u1g2000pre.googlegroups.com...
Obviously respect for people
trying to help you is something that you have not learned from the
MAs...which you should have done.
Bwahahahahahahaha. Welcome to rec,martial-arts.
Fraser
Appledog
> "Daniel" <nidan.da...@gmail.com> wrote in message
Just because you admit you're doing it doesn't mean you are somehow
right or credible in doing so.
-
Androcles
"Daniel" <nidan...@gmail.com> wrote in message
news:a387670b-dc11-43ae...@u1g2000pre.googlegroups.com...
Daniel
===============================================
? (hook)
|
|
| (bar)
|
|
? (hook)
|
|
| (bar)
|
|
54321012345 (bar at right angles, attached at 0)
I'll not be sarcastic, I'll be direct instead. You are a fuckin'
pompous idiot. End of undesirable discussion.
*plonk*
Do not reply to this generic message, it was automatically generated;
you have been kill-filed, either for being boringly stupid, repetitive,
unfunny, ineducable, repeatedly posting politics, religion or off-topic
subjects to a sci. newsgroup, attempting cheapskate free advertising
for profit, because you are a troll, simply insane or any combination
or permutation of the aforementioned reasons; any reply will go unread.
Boringly stupid is the most common cause of kill-filing, but because
this message is generic the other reasons have been included. You are
left to decide which is most applicable to you.
There is no appeal, I have despotic power over whom I will electronically
admit into my home and you do not qualify as a reasonable person I would
wish to converse with or even poke fun at. Some weirdoes are not kill-
filed, they amuse me and I retain them for their entertainment value
as I would any chicken with two heads, either one of which enables the
dumb bird to scratch dirt, step back, look down, step forward to the
same spot and repeat the process eternally.
This should not trouble you, many of those plonked find it a blessing
that they are not required to think and can persist in their bigotry
or crackpot theories without challenge.
You have the right to free speech, I have the right not to listen. The
kill-file will be cleared annually with spring cleaning or whenever I
purchase a new computer or hard drive.
I'm fully aware that you may be so stupid as to reply, but the purpose
of this message is to encourage others to kill-file fuckwits like you.
I hope you find this explanation is satisfactory but even if you don't,
damnly my frank, I don't give a dear. Have a nice day and fuck off.
Shuurai
> But Newton's physics tells us an isolated body
> cannot generate net momentum; action = reaction.
> without the arm swing. So the question is, did this
> trick really work as a cheat, physically? Or was
> it just an illusion?
You're shifting your center of gravity.
Think of your body as being a lever; the fulcrum is your lower back.
When your arms are on your chest or behind your neck, they're on the
side of the lever you are lifting. When you throw them towards your
feet, most of their weight is either above the fulcrum or even past
it; which means you are lifting less when you sit upright.
Appledog
> > But Newton's physics tells us an isolated body
> > cannot generate net momentum; action = reaction.
> > But I swear I couldn't have completed that segment
> > without the arm swing. So the question is, did this
> > trick really work as a cheat, physically? Or was
> > it just an illusion?
>
> You're shifting your center of gravity.
An isolated body can't shift it's center of gravity.
-
Androcles
"Appledog" <oliver....@gmail.com> wrote in message
news:73afd4ba-da1a-42ca...@f20g2000prn.googlegroups.com...
===================================
Take a straight rod and bend it. The CoG moves from
inside the rod to outside. Engage brain before opening mouth.
Better yet, don't open mouth.
Appledog
> "Appledog" <oliver.rich...@gmail.com> wrote in message
As it's an isolated body, please explain how the center of gravity has
changed location in space, since there was no other body on which to
exert a force.
If what you were really saying were true, then bending over would be a
form of propulsion. It's not in all cases, and you're not getting
anywhere with it either.
-
RichD
> > Really? You mean, the seat support chains no
> > longer hang like a plumb line, aimed at the earth's
> > center? You might want to publish this discovery,
> > in a more prestigious journal than Usenet...
>
> Sarcasm is inappropriate when someone is doing his
> best to explain something to you, even if they are wrong.
ya bwana! In the future, I shall take into account
your tender sensibilities, as my highest priority...
> Obviously respect for people trying to help you
> is something that you have not learned from the
> MAs...which you should have done.
The purpose of MA is to discombobulate
another human being, not respect him.
That's boy scout myth, for children.
> Take a rigid steel bar with a hook at 1 end. Hang it from a point
> above using the hook. Measure angle relative to a normal from the
> Earth's surface. It will be 0 degrees. Now, at the bottom of the bar
> fix another bar at right angles to the hanging bar. Measure angle
> deviation of hanging bar to what it was before. 0 degrees? I doubt it.
I think you are right.
When you kick forward and lean back, it shifts
the c.o.g. backward, which creates a torque
through gravity. This nudges the swing forward,
overcoming frictional losses.
Funny how something so simple, any 5 year old
can do it, but us science nerds have to scratch
our heads to suss it out.
> If you desire to continue this discussion I am happy to...
> as i find it interesting and possibly mutually informative...
> however a masochist I am not..and if you continue your
> sarcastic put-downs then I see no
> need to continue this discussion.
I will respect you like they taught me in MA school.
--
Rich
Androcles
=======================================
The only objects referred to in your sentence above are
"a body " and "center of gravity".
"Location in space" is not a reference and you gave no
mention of a location in space when you made your false
claim.
I have pointed out that bending a rod shifts it CoG
(relative to the end points of the rod, although that
should have been obvious).
What I'm really saying is true, and I have not claimed
bending would be a form of propulsion since I have
offered no reference that it would move relatively to
other than the body relative to the centre of gravity or
the centre of gravity relative to the body.
Appledog
I don't accept your premise that it was a false claim and I'll point
out here that it was intellectually dishonest of you to say that.
Anyways, an isolated body exists in space - if you can't fathom that I
don't know what else I could tell you. If there's no space as a
reference please tell me how you know the object was bent, since there
is no way to tell if the object is straight or bent given that there
is no space. Yes I am being facetious :)
> I have pointed out that bending a rod shifts it CoG
> (relative to the end points of the rod, although that
> should have been obvious).
It was blatantly obvious. The center of gravity shifted relative to
the end points of the rod. However, the center of gravity did not
actually move. It is equally as fair to say that the ends of the rod
shifted relative to the center of gravity. It is, in fact, more fair;
since by stating this is an isolated body, with the question of how it
is to get it's center of gravity to move...
but you seem to have missed this in your zeal to narrowly define the
problem and insist that we are dealing with the CoG relative to the
shape of the object. To remind you, we're not, we're discussing if an
isolated body can shift it's center of gravity, which it cannot do.
> What I'm really saying is true, and I have not claimed
> bending would be a form of propulsion since I have
> offered no reference that it would move relatively to
> other than the body relative to the centre of gravity or
> the centre of gravity relative to the body.
If by bending the object can shift it's center of gravity, then it
could be used as a form of propulsion. As the center of gravity
changes it's position by accelerating due to the bending, due to
newton's laws it would continue moving in whatever direction. This is
clearly impossible, so what you say is actually a false claim.
I was actually expecting your little killfile speech as a reply to the
previous message. Will you be posting it now?
-
prince8585
hello friends,
how the heck can a child sitting on a stationary
playground swing eventually pump herself up to a wide arc of swing,
touching her feet to the ground?
--
prince8585
Androcles
========================================
I don't accept your blatant lie that "An isolated body can't shift
it's center of gravity" and I'll point out here that it was dishonest
of you to say that; and I'll also point out you have no intellect.
========================================
Anyways, an isolated body exists in space - if you can't fathom that I
don't know what else I could tell you.
========================================
Space is nothing and extends to infinity omnidirectionally.
The origin of coordinates is anywhere I choose it to be.
As a matter of convenience I shall choose the CoG of the
isolated human being as the origin of coordinates, he will
be free to bend as he chooses. If you can't fathom that out
you don't know what else you can tell me, but whatever you
tell me I won't accept your unintellectual dishonesty.
========================================
If there's no space as a
reference please tell me how you know the object was bent, since there
is no way to tell if the object is straight or bent given that there
is no space. Yes I am being facetious :)
==========================================
I'll remind you of the thread title, "the physics of sit-ups".
The object is known to be straight or bent by the position of
its centre of gravity which will be inside when straight and outside
when bent, thereby proving your blatant lie was a falsehood.
==========================================
> I have pointed out that bending a rod shifts it CoG
> (relative to the end points of the rod, although that
> should have been obvious).
It was blatantly obvious. The center of gravity shifted relative to
the end points of the rod. However, the center of gravity did not
actually move.
===========================================
All movement is relative. There is no absolute frame of reference
against which movement can be measured. Therefore the CoG
moved relative to the body when the body changed shape.
===========================================
It is equally as fair to say that the ends of the rod
shifted relative to the center of gravity.
============================================
Correct, so a centre of gravity can shift its isolated body.
============================================
It is, in fact, more fair;
============================================
Dishonest. "All animals are equal, but some are more equal
that others" -- 'Animal Farm', George Orwell.
Your facetiousness is no match for Orwell's intellectual mirth.
============================================
since by stating this is an isolated body, with the question of how it
is to get it's center of gravity to move...
============================================
All motion is relative, the station comes to the train. See the
intellectuals Nicholas Copernicus and Galileo Galilei.
The isolated body of the Earth would still be the unintellectual centre
of the universe if it and its centre of gravity did not move relatively
to some other (isolated) body. However, you are free to choose any
origin of coordinates and calculate the motion of stars and planets
around the Earth if you wish. Those motions will be horrendously
complicated, notably retrograde motion, which is why the geocentric
model was abandoned and the heliocentric model adopted.
http://www.truthonline.co.uk/retromars05.jpg
The retrograde motion of Mars in 2005.
A composite image created by superimposing images taken on 35 different
dates,
each separated from the next by about a week.
============================================
but you seem to have missed this in your zeal to narrowly define the
problem and insist that we are dealing with the CoG relative to the
shape of the object. To remind you, we're not, we're discussing if an
isolated body can shift it's center of gravity, which it cannot do.
============================================
You've already conceded the ends of the rod shift relative to
the centre of gravity. Therefore by the principle of relativity a centre
of gravity can shift its isolated body and an isolated body can shift its
centre of gravity.
And yes, I have defined the problem narrowly because the problem
requires a narrow definition. The problem is really your faith in a
universal frame of reference that you call "space" (really nothing)
against which no motion supposedly takes place. You don't
want isolation as in the Moon is isolated from the Earth, you
want a universe in which there is only one body and that body
is at the centre of your hypothetical universe. Such a universe
is remote from reality.
============================================
> What I'm really saying is true, and I have not claimed
> bending would be a form of propulsion since I have
> offered no reference that it would move relatively to
> other than the body relative to the centre of gravity or
> the centre of gravity relative to the body.
If by bending the object can shift it's center of gravity, then it
could be used as a form of propulsion.
=========================================
Nope. You'd need somewhere to go, some other isolated
body to approach or recede from. Bending will not do that.
=========================================
As the center of gravity
changes it's position by accelerating due to the bending, due to
newton's laws it would continue moving in whatever direction. This is
clearly impossible, so what you say is actually a false claim.
=============================================
Not at all. The acceleration is matched by the following deceleration
as the bending comes to a halt, and in any case one half bends in
the opposite direction to the other. The net momentum sums to zero.
=============================================
I was actually expecting your little killfile speech as a reply to the
previous message. Will you be posting it now?
==============================================
Not yet. I don't mind teaching those willing to learn and I'm
giving you the opportunity to do that. You are coming close,
though, with accusations of intellectual dishonesty.
Appledog
>
> Space is nothing and extends to infinity omnidirectionally.
> The origin of coordinates is anywhere I choose it to be.
Here is where we disagree. I conceive of the universe in a
fundamentally different way than you do - for example, to me space is
a thing, which exists, and has physical properties, such as the
ability to curve. Einstein, Feynman, and most of the great physicists
thought of the universe in the same way - check out the "gravity is
not a force" articles out there for a taste of what I'm getting at, if
you're interested. I'll say this much, the model I use fits
experimental evidence a lot better than what you are proposing, but
they both have their place.
> If you can't fathom that out
> you don't know what else you can tell me, but whatever you
> tell me I won't accept your unintellectual dishonesty.
At this point I've moved beyond your claims of intellectual
dishonesty, ignorance, blatant lying, and so forth. I simply don't
care. I'll deal with the issues that interest me, though, such as the
above.
> If there's no space as a
> reference please tell me how you know the object was bent, since there
> is no way to tell if the object is straight or bent given that there
> is no space. Yes I am being facetious :)
>
> ==========================================
> I'll remind you of the thread title, "the physics of sit-ups".
> The object is known to be straight or bent by the position of
> its centre of gravity which will be inside when straight and outside
> when bent, thereby proving your blatant lie was a falsehood.
I'll remind you of the thread title. The concept of an isolated body
is not correct here since someone doing situps has a connection to the
ground. This was pointed out early in the thread so I will not get
into it here. But if you're interested, go and check for yourself. You
will surely find the messages there, near the top of the thread.
> All movement is relative. There is no absolute frame of reference
> against which movement can be measured. Therefore the CoG
> moved relative to the body when the body changed shape.
There is no absolute frame of reference against which movement can be
measured, "therefore" the CoG moved relative to the body, meaning,
there is no absolute frame of reference therefore we will use the
frame of reference relative to itself?
Why?
Why not use the frame of reference implied by the original example, in
explaining how wailing your arms makes situps easier? The problem is
that if you don't assume the frame of reference is the space around
the body, considering an isolated body no longer applies to the
question. In that case, most of what you are saying is irrelevant to
this discussion. It's valid in it's own way, it just doesn't apply,
that's all.
> You've already conceded the ends of the rod shift relative to
> the centre of gravity. Therefore by the principle of relativity a centre
> of gravity can shift its isolated body and an isolated body can shift its
> centre of gravity.
Only if you are assuming the ends of the rod are fixed in space. Which
you cannot do, since you have no frame of reference for doing so. The
only question here is if the center of gravity moves. If we can't
answer it that way then it doesn't apply to the situps question.
> And yes, I have defined the problem narrowly because the problem
> requires a narrow definition. The problem is really your faith in a
> universal frame of reference that you call "space" (really nothing)
If it's nothing then how can it curve?
> against which no motion supposedly takes place.
...which is one of the great mysteries (well not really a mystery).
There's no actual motion, except you're accelerating. Think about it -
it's fascinating. And when you figure it out you will laugh.
>You don't
> want isolation as in the Moon is isolated from the Earth, you
> want a universe in which there is only one body and that body
> is at the centre of your hypothetical universe. Such a universe
> is remote from reality.
No, you don't want that, because that has nothing to do with situps.
You've misunderstood the actual problem being discussed and why the
term isolated body was mentioned in the first place. As this is
starting to get repetitive I'll cut it short.
> Not yet. I don't mind teaching those willing to learn and I'm
> giving you the opportunity to do that. You are coming close,
> though, with accusations of intellectual dishonesty.
As have you. But if I killfile you, I won't announce it, because I
don't care about my reputation here nor what people think of me, on
any level. Good day :)
-
Shuurai
> > You're shifting your center of gravity.
>
> An isolated body can't shift it's center of gravity.
An isolated body? What isolated body?!? You're lying on the GROUND
when you perform a sit-up; there is nothing "isolated" about it; you
are moving against the mass of the Earth.
And even if there were an isolated body involved, your premise is also
wrong. Your center of gravity is your center of mass; as long as you
are capable of changing the configuration of your mass, you can by
definition change your center of gravity.
Appledog
> > > You're shifting your center of gravity.
>
> > An isolated body can't shift it's center of gravity.
>
> An isolated body? What isolated body?!? You're lying on the GROUND
> when you perform a sit-up; there is nothing "isolated" about it; you
> are moving against the mass of the Earth.
Exactly. Which is why wailing your arms enables you to shift your
center of gravity. If you recall, you had replied as follows to RichD:
RichD >> But Newton's physics tells us an isolated body
RichD >> cannot generate net momentum; [snip]
Shuurai > You're shifting your center of gravity.
The correct time to talk about "what isolated body" was in response to
RichD, not in response to me, reminding you that you failed to mention
it in response to RichD ;-)
> And even if there were an isolated body involved, your premise is also
> wrong. Your center of gravity is your center of mass; as long as you
> are capable of changing the configuration of your mass, you can by
> definition change your center of gravity.
But not it's location in space. Which is why the "isolated body" idea
is not relevant to what RichD was asking.
-
Androcles
On Dec 7, 11:43 pm, "Androcles" <Headmas...@Hogwarts.physics_q> wrote:
>
> Space is nothing and extends to infinity omnidirectionally.
> The origin of coordinates is anywhere I choose it to be.
Here is where we disagree. I conceive of the universe in a
fundamentally different way than you do - for example, to me space is
a thing, which exists, and has physical properties, such as the
ability to curve.
==========================================
Ok, so we disagree. If space is curved, is it convex or concave?
http://www.androcles01.pwp.blueyonder.co.uk/Shapiro/Crapiro.htm
==========================================
Einstein, Feynman, and most of the great physicists
thought of the universe in the same way - check out the "gravity is
not a force" articles out there for a taste of what I'm getting at, if
you're interested. I'll say this much, the model I use fits
experimental evidence a lot better than what you are proposing, but
they both have their place.
==========================================
Einstein was a dishonest fuckwit and if you want to argue the point,
present the evidence.
Isaac Asimov wrote in "Quasar, Quasar, Burning Bright" ,
ISBN 0-380-44610-3
(concerning life after death)
[ If you want to argue the point, present the evidence.
I must warn you, though, that there are some arguments I will not
accept.
I won't accept any argument from authority. ("The Bible says so")
I won't accept any argument from internal conviction ("I have faith it
is so")
I won't accept any argument from personal abuse ("What are you, an
atheist?")
I won't accept any argument from irrelevance ("Do you think you have
been put on this Earth just to exist for a moment of time?)
I won't accept any argument from anecdote ("My cousin has a friend who
went to a medium and talked to her dead husband")
And when all that, and other varieties of non-evidence are eliminated,
there turns out to be nothing.]
Appledog
>
> > Space is nothing and extends to infinity omnidirectionally.
> > The origin of coordinates is anywhere I choose it to be.
>
> Here is where we disagree. I conceive of the universe in a
> fundamentally different way than you do - for example, to me space is
> a thing, which exists, and has physical properties, such as the
> ability to curve.
> ==========================================
> Ok, so we disagree. If space is curved, is it convex or concave?
> http://www.androcles01.pwp.blueyonder.co.uk/Shapiro/Crapiro.htm
I'm not sure why you've included that link; the diagram is clearly
false, as it implies that the earth travels more than 20% of it's
orbit during the time it would take light to make a round trip to mars
(note: less than 10 minutes, probably closer to 7). It also seems to
imply that light does not take the path of least distance (in this
case, least time), particularly in the right half of the example.
As to convex or concave, the question has meaning if you consider only
one or two dimensions of space, i.e. a plane. And there are certainly
methods which will prove this to you, so long as you fully understand
what you are asking for. As you are asking for a definition of convex
or concave, this would only have a meaning for a flat surface (a 2
dimensional plane). Only such a thing can be convex or concave. A
ball, for example, is neither convex nor concave in the same way a
plane is. (BTW, although I provide a two dimensional example here,
feel FREE to expand or reduce the number of dimensions you want to
deal in, as I am capable of providing examples for any number of
dimensions we may measure).
Ok here's what you do: take a hula hoop. A very, very large hula hoop.
Measure the circumfrence. Now measure the diameter. You will find that
the formula "radius equals two pi squared" does not match with
experimental evidence. The reason for this is that what appears to be
a flat, 2 dimensional surface to you, is in fact curved. Also you may
realize in this case that it does not matter if it is convex or
concave, however the larger your hula hoop, the more obvious it will
be to you that in this case the space is "convex", although biconvex,
or spherical may be a more appropriate answer considering the whole of
what you are actually measuring.
"empty space" is much the same and an extremely surprising observation
can easily be made in a way very similar to what I have described
above, which shows how space can curve. Further that it curves,
essentially, concave. Although again, there are other terms which are
more appropriate to describing things in that number of dimensions.
> Einstein was a dishonest fuckwit and if you want to argue the point,
> present the evidence.
As your claim that he was a dishonest fuckwit is, to me, proof enough,
I do not see any reason to present further evidence. If you want, you
can do the experiment I described yourself.
> I must warn you, though, that there are some arguments I will not
> accept.
Oh, I've figured that much out on my own :) I'm just interested in
seeing how far you will go to defend your windmill.
-
Androcles
On Dec 8, 12:36 am, "Androcles" <Headmas...@Hogwarts.physics_q> wrote:
>
> > Space is nothing and extends to infinity omnidirectionally.
> > The origin of coordinates is anywhere I choose it to be.
>
> Here is where we disagree. I conceive of the universe in a
> fundamentally different way than you do - for example, to me space is
> a thing, which exists, and has physical properties, such as the
> ability to curve.
> ==========================================
> Ok, so we disagree. If space is curved, is it convex or concave?
> http://www.androcles01.pwp.blueyonder.co.uk/Shapiro/Crapiro.htm
I'm not sure why you've included that link; the diagram is clearly
false, as it implies that the earth travels more than 20% of it's
orbit during the time it would take light to make a round trip to mars
(note: less than 10 minutes, probably closer to 7).
==============================================
It's exaggerated. The principle of it is not. If space is curved,
is it convex or concave?
I'm quite certain you can't answer a straight-forward question
and are complete clueless, relying on the bullshit of others
rather than thinking. That is where we disagree.
As this is getting rather lowbrow as you demonstrate
your pathetic Neanderthal intellect, I've cut this short.
Shuurai
> > > > You're shifting your center of gravity.
>
> > > An isolated body can't shift it's center of gravity.
>
> > An isolated body? What isolated body?!? You're lying on the GROUND
> > when you perform a sit-up; there is nothing "isolated" about it; you
> > are moving against the mass of the Earth.
>
> Exactly. Which is why wailing your arms enables you to shift your
> center of gravity. If you recall, you had replied as follows to RichD:
Then why did you respond to me saying that an isolated body can't
shift it's center of gravity?
> RichD >> But Newton's physics tells us an isolated body
> RichD >> cannot generate net momentum; [snip]
> Shuurai > You're shifting your center of gravity.
>
> The correct time to talk about "what isolated body" was in response to
> RichD, not in response to me, reminding you that you failed to mention
> it in response to RichD ;-)
Failed to mention what? There was no need for me to mention any
isolated body in my response to him; there is no isolated body
involved in the process.
> > And even if there were an isolated body involved, your premise is also
> > wrong. Your center of gravity is your center of mass; as long as you
> > are capable of changing the configuration of your mass, you can by
> > definition change your center of gravity.
>
> But not it's location in space. Which is why the "isolated body" idea
> is not relevant to what RichD was asking.
Then what was the purpose of your statement that an isolated body
can't shift it's center of gravity?
Neil Gendzwill
divers for example could start their body twisting without an initial moment and nothing to push off of. Not available online but
I'm sure you could get it through the library - google search reveals a lot of references to the article.
Neil
Appledog
> "Appledog" <oliver.rich...@gmail.com> wrote in message
>
> news:d1cee30b-c5f7-41ae...@u25g2000prh.googlegroups.com...
> On Dec 8, 12:36 am, "Androcles" <Headmas...@Hogwarts.physics_q> wrote:
>
>
>
> > > Space is nothing and extends to infinity omnidirectionally.
> > > The origin of coordinates is anywhere I choose it to be.
>
> > Here is where we disagree. I conceive of the universe in a
> > fundamentally different way than you do - for example, to me space is
> > a thing, which exists, and has physical properties, such as the
> > ability to curve.
> > ==========================================
> > Ok, so we disagree. If space is curved, is it convex or concave?
> >http://www.androcles01.pwp.blueyonder.co.uk/Shapiro/Crapiro.htm
>
> I'm not sure why you've included that link; the diagram is clearly
> false, as it implies that the earth travels more than 20% of it's
> orbit during the time it would take light to make a round trip to mars
> (note: less than 10 minutes, probably closer to 7).
> ==============================================
> It's exaggerated. The principle of it is not. If space is curved,
> is it convex or concave?
Sorry, did you want me to cut and paste the hula hoop experiment
again? You ARE aware I answered your question, aren't you? Will you
read it this time? Here's the cut and paste you failed to read and
respond to from the last post:
"Ok here's what you do: take a hula hoop. A very, very large hula
hoop. Measure the circumfrence. Now measure the diameter. You will
find that the formula "radius equals two pi squared" does not match
with experimental evidence. The reason for this is that what appears
to be a flat, 2 dimensional surface to you, is in fact curved. Also
you may realize in this case that it does not matter if it is convex
or concave, however the larger your hula hoop, the more obvious it
will be to you that in this case the space is "convex", although
biconvex, or spherical may be a more appropriate answer considering
the whole of what you are actually measuring. "
An easier formula for someone of your capabilities would be C = pi *
diameter. You will find that the formula, which SHOULD work, since PI
is the circumference divided by the diameter, does not actually yield
pi; in fact it yields a SMALLER value, consistently. You will actually
find that at some point, PI IS EXACTLY THREE. Before decreasing yet
further in a fit of apparent madness. Eventually it will reach one.
The logical absurdity, and the repetitive nature of this experiment
belie it's simplicity and it's accuracy for measuring curved space on
a 2 dimensional plane.
Again if you'd like an example which works for measuring curved space
in our perceptible 4 dimensional universe, let me know.
> I'm quite certain you can't answer a straight-forward question
> and are complete clueless, relying on the bullshit of others
> rather than thinking. That is where we disagree.
Yes, that is indeed where we disagree, as I have now answered your
question twice. I've even simplified it the second time around.
> As this is getting rather lowbrow as you demonstrate
> your pathetic Neanderthal intellect, I've cut this short.
Yes, because as well all know, you not being able to understand a
simple equation like circumference over diameter means that I am the
one with a pathetic, Neanderthal intellect.
Lol, what a kook.
-
Androcles
On Dec 8, 1:37 am, "Androcles" <Headmas...@Hogwarts.physics_q> wrote:
> "Appledog" <oliver.rich...@gmail.com> wrote in message
>
> news:d1cee30b-c5f7-41ae...@u25g2000prh.googlegroups.com...
> On Dec 8, 12:36 am, "Androcles" <Headmas...@Hogwarts.physics_q> wrote:
>
>
>
> > > Space is nothing and extends to infinity omnidirectionally.
> > > The origin of coordinates is anywhere I choose it to be.
>
> > Here is where we disagree. I conceive of the universe in a
> > fundamentally different way than you do - for example, to me space is
> > a thing, which exists, and has physical properties, such as the
> > ability to curve.
> > ==========================================
> > Ok, so we disagree. If space is curved, is it convex or concave?
> >http://www.androcles01.pwp.blueyonder.co.uk/Shapiro/Crapiro.htm
>
> I'm not sure why you've included that link; the diagram is clearly
> false, as it implies that the earth travels more than 20% of it's
> orbit during the time it would take light to make a round trip to mars
> (note: less than 10 minutes, probably closer to 7).
> ==============================================
> It's exaggerated. The principle of it is not. If space is curved,
> is it convex or concave?
Sorry, did you want me to cut and paste the hula hoop experiment
again?
================================================
No, I want you to answer the fuckin' question.
If space is curved, is it convex or concave ...err... shithead?
Appledog
> > > > > You're shifting your center of gravity.
>
> > > > An isolated body can't shift it's center of gravity.
>
> > > An isolated body? What isolated body?!? You're lying on the GROUND
> > > when you perform a sit-up; there is nothing "isolated" about it; you
> > > are moving against the mass of the Earth.
>
> > Exactly. Which is why wailing your arms enables you to shift your
> > center of gravity. If you recall, you had replied as follows to RichD:
>
> Then why did you respond to me saying that an isolated body can't
> shift it's center of gravity?
Because you apparently missed it in RichD's message and knowing how
much you know about science, I just wanted to point out the error so
it didn't embarrass you further.
> > RichD >> But Newton's physics tells us an isolated body
> > RichD >> cannot generate net momentum; [snip]
> > Shuurai > You're shifting your center of gravity.
>
> > The correct time to talk about "what isolated body" was in response to
> > RichD, not in response to me, reminding you that you failed to mention
> > it in response to RichD ;-)
>
> Failed to mention what? There was no need for me to mention any
> isolated body in my response to him; there is no isolated body
> involved in the process.
I know that, which is why I mentioned it. You seemed to have forgotten
thatthere is no isolated body; in lieu of the fact that RichD said,
"...an isolated body..." in reference to the situps example. In short,
in failing to comprehend his error (and now, your own, over several
posts calmly explaining it to you) made the error your own. Now, me,
what I am doing here, by mentioning it, and going over it, over and
over, is informing you of your mistake. You're free to disagree, of
course - and knowing how you act on here you definately will. Even
before reading what I have to write. But you're still wrong, because
as you say, an isolated body cannot shift it's center of gravity.
You're one of those rare people that will agree with the principle and
then immediately disagree with everything else, regardless of the fact
that all I ever said in the OP was the principle itself. Other notable
idiots like this are nemo and herb (both canon and -zet).
> > > And even if there were an isolated body involved, your premise is also
> > > wrong. Your center of gravity is your center of mass; as long as you
> > > are capable of changing the configuration of your mass, you can by
> > > definition change your center of gravity.
>
> > But not it's location in space. Which is why the "isolated body" idea
> > is not relevant to what RichD was asking.
>
> Then what was the purpose of your statement that an isolated body
> can't shift it's center of gravity?
Lol! You're such a card. It wasn't my statement, dearest Shuurai. It
was RichD's. And later yours. Yet I am sure you really believe it was
my statement, after all you are incapable of admitting any error no
matter how slight. Oh, the fun this is! The times we are having. I am
sure you will look back at all this one day and laugh. And laugh. Not
because you are mentally retarded, mind you, but because I believe
deep down in my heart you're not, and that you are actually capable of
figuring this all out if you try, and I believe it will be funny to
you.
-
Appledog
I might point out that a bird can also fly, and a fish can swim,
without having anything to push off of. Actually, I'd be interesting
in reading the article, but I don't for one moment believe they can
start rotating without having anything to push off of. That would of
course imply frictionless acceleration is possible. I hope I am not
notpicking too much here Neil, I am sure it looks like it shouldn't be
possible what they're doing but there must be a real, simple,
scientific, physical explanation for what is going on - just like
there is for everything else in the martial arts. That's always been
the case with everything I've seen so far so I doubt it would be any
different for anything else.
-
Androcles
On Dec 8, 4:36 am, Neil Gendzwill <ngendzw...@yahoo.com> wrote:
> I recall an old article in Scientific American from 1980 called "The
> Physics of Somersaulting and Twisting". It described how
> divers for example could start their body twisting without an initial
> moment and nothing to push off of. Not available online but
> I'm sure you could get it through the library - google search reveals a
> lot of references to the article.
>
> Neil
I might point out that a bird can also fly, and a fish can swim,
without having anything to push off of.
===========================================
I might point out that air and water are not "nothing" but something
to push off of... err... idiot.
===========================================
RichD
That's a thought. However, if you follow that logic,
we can infer that the arms should be held forward
throughout, which does not feel right (though it
may be correct, physically).
It also does not explain the feeling that throwing
the arms forward, hard, creates 'lift'. If it's merely
a matter of 'lightening the load', one might get
the same effect by thrusting the arms gently,
which doesn't work, subjectively.
--
Rich
Fraser Johnston
"Appledog" <oliver....@gmail.com> wrote in message
news:7f3041fa-34fe-42d2...@g1g2000pra.googlegroups.com...
I might point out that a bird can also fly, and a fish can swim,
without having anything to push off of.
+++++++++++++++++++++++++++++++++++++++++++
Except of course air and water. They couldn't do it in a vacuum. Are you
really that stupid or is this some more champagne trolling?
Fraser
herbzet
Appledog wrote:
> Neil Gendzwill wrote:
> >
> > I recall an old article in Scientific American from 1980 called
> > "The Physics of Somersaulting and Twisting". It described how
> > divers for example could start their body twisting without an
> > initial moment and nothing to push off of. Not available online but
> > I'm sure you could get it through the library - google search reveals
> > a lot of references to the article.
>
> I might point out that a bird can also fly, and a fish can swim,
> without having anything to push off of.
Lol, that's almost as good as "radius equals two pi squared"!
> Actually, I'd be interesting
> in reading the article, but I don't for one moment believe they can
> start rotating without having anything to push off of.
Then you probably won't believe that if you drop a cat spine-down,
it will rotate to land feet-down.
> That would of
> course imply frictionless acceleration is possible. I hope I am not
> notpicking too much here Neil, I am sure it looks like it shouldn't be
> possible what they're doing but there must be a real, simple,
> scientific, physical explanation for what is going on - just like
> there is for everything else in the martial arts. That's always been
> the case with everything I've seen so far so I doubt it would be any
> different for anything else.
--
hz
Appledog
> "Appledog" <oliver.rich...@gmail.com> wrote in message
Sorry but did Neil actually say "It described how divers for example
could start their body twisting without an initial moment and nothing
to push off of." in the post I was replying to? Come on Fraser. You're
not that dense! ;-)
-
Appledog
> Appledog wrote:
> > Neil Gendzwill wrote:
>
> > > I recall an old article in Scientific American from 1980 called
> > > "The Physics of Somersaulting and Twisting". It described how
> > > divers for example could start their body twisting without an
> > > initial moment and nothing to push off of. Not available online but
> > > I'm sure you could get it through the library - google search reveals
> > > a lot of references to the article.
>
> > I might point out that a bird can also fly, and a fish can swim,
> > without having anything to push off of.
>
> Lol, that's almost as good as "radius equals two pi squared"!
Or even funnier, "It described how divers for example could start
their body twisting without an initial moment and nothing to push off
of."
Boy, do you ever have egg on your face!
The funny part is that you even left the following tagged onto your
post, as if you not only hadn't had the time to snip it, but read it
as well:
> > That would of
> > course imply frictionless acceleration is possible. I hope I am not
> > nitpicking too much here Neil, I am sure it looks like it shouldn't be
> > possible what they're doing but there must be a real, simple,
> > scientific, physical explanation for what is going on - just like
> > there is for everything else in the martial arts. That's always been
> > the case with everything I've seen so far so I doubt it would be any
> > different for anything else.
Anyways. Have a nice life, idiot.
-
Shuurai
> > Then why did you respond to me saying that an isolated body can't
> > shift it's center of gravity?
>
> Because you apparently missed it in RichD's message and knowing how
> much you know about science, I just wanted to point out the error so
> it didn't embarrass you further.
And so you decided to respond with an incorrect statement?
> > Failed to mention what? There was no need for me to mention any
> > isolated body in my response to him; there is no isolated body
> > involved in the process.
>
> I know that, which is why I mentioned it.
You know there was no need for me to mention an isolated body, so you
decided to mention an isolated body (within an incorrect statement) in
order to accomplish what?
Admit it Ollie, the reason you "mentioned" it was because you wanted
to take part in a discussion that was beyond your abilities; which is
pretty sad considering this is high school level science. You failed
to notice that your statement made no sense, and now that it's been
pointed out to you that it was wrong, you're trying desperately to
pretend that someone else is to blame for you making an ass of
yourself.
> You seemed to have forgotten
> thatthere is no isolated body; in lieu of the fact that RichD said,
> "...an isolated body..." in reference to the situps example.
Shame on you, Ollie. Editing his statement as though you think nobody
will notice. What he said was that an isolated body cannot generate
net momentum; YOUR statement was that an isolated body cannot shift
it's center of gravity.
> In short, in failing to comprehend his error (and now, your own, over several
> posts calmly explaining it to you) made the error your own.
So according to you, by not including a false statement about
something irrelevant to my response, I somehow committed an error?
> Now, me, what I am doing here, by mentioning it, and going over it, over and
> over, is informing you of your mistake.
No, Ollie. What you are doing here is trying deperately to save face
after having made an asinine statement. You know, your usual routine.
> You're free to disagree, of
> course - and knowing how you act on here you definately will. Even
> before reading what I have to write. But you're still wrong, because
> as you say, an isolated body cannot shift it's center of gravity.
That's not what I said, Ollie - nor is it what RichD said. It's what
YOU said, and it's incorrect.
> You're one of those rare people that will agree with the principle and
> then immediately disagree with everything else, regardless of the fact
> that all I ever said in the OP was the principle itself. Other notable
> idiots like this are nemo and herb (both canon and -zet).
What you said was this: "An isolated body can't shift it's center of
gravity."
http://groups.google.com/group/rec.martial-arts/msg/c161ee4a56a8ccae
> > Then what was the purpose of your statement that an isolated body
> > can't shift it's center of gravity?
>
> Lol! You're such a card. It wasn't my statement, dearest Shuurai.
It was your statement, sweetie:
http://groups.google.com/group/rec.martial-arts/msg/c161ee4a56a8ccae
> It was RichD's.
Wrong again. RichD said that an isolated body cannot generate net
momentum. Do you see the difference?
> And later yours.
Nope; was never my statement.
> Yet I am sure you really believe it was
> my statement, after all you are incapable of admitting any error no
> matter how slight.
Google believes it was your statement:
http://groups.google.com/group/rec.martial-arts/msg/c161ee4a56a8ccae
Of course, you are free to delete the post and pretend that you never
wrote it, but nobody will believe you this time any more than they did
the last time you pulled that shit.
> Oh, the fun this is!
I agree. I think it's hilarious to watch you dance.
> The times we are having. I am
> sure you will look back at all this one day and laugh. And laugh. Not
> because you are mentally retarded, mind you, but because I believe
> deep down in my heart you're not, and that you are actually capable of
> figuring this all out if you try, and I believe it will be funny to
> you.
Hell, I'm laughing at you now.
Neil Gendzwill
>
> Or even funnier, "It described how divers for example could start
> their body twisting without an initial moment and nothing to push off
> of."
Found another article discussing similar stuff. Turns out it's not without an initial moment. The subject under discussion in this
case is how divers can start twisting in mid-air without initiating it off the board. Turns out you need some angular momentum and
then you can change the vectors of that momentum because the human body is not a rigid system. However the article states that the
mechanism is not yet fully understood (at least in 1997 when it was written).
Brief but interesting read here:
http://www.usa-gymnastics.org/home/publications/technique/1997/2/twist.pdf
Neil
Appledog
> > > Then why did you respond to me saying that an isolated body can't
> > > shift it's center of gravity?
>
> > Because you apparently missed it in RichD's message and knowing how
> > much you know about science, I just wanted to point out the error so
> > it didn't embarrass you further.
>
> And so you decided to respond with an incorrect statement?
If you can't understand sarcasm that isn't my problem.
> > > Failed to mention what? There was no need for me to mention any
> > > isolated body in my response to him; there is no isolated body
> > > involved in the process.
>
> > I know that, which is why I mentioned it.
>
> You know there was no need for me to mention an isolated body, so you
> decided to mention an isolated body (within an incorrect statement) in
> order to accomplish what?
To show you that you were operating under a delusion posted in RichD's
message. What the fuck is wrong with you that you will talk to RichD
and accept his premise, which is "...an isolated body..." but you
start arguing with me when I point out that both of you are wrong?
> Admit it Ollie, the reason you "mentioned" it was because you wanted
> to take part in a discussion that was beyond your abilities; which is
> pretty sad considering this is high school level science. You failed
> to notice that your statement made no sense, and now that it's been
> pointed out to you that it was wrong, you're trying desperately to
> pretend that someone else is to blame for you making an ass of
> yourself.
Dear lord. You're mentally retarded, aren't you?
> That's not what I said, Ollie - nor is it what RichD said. It's what
> YOU said, and it's incorrect.
No, actually, it's what RichD said and what you took and ran with.
DIdn't you see the quote I provided you? Oh, of course not.. you
apparently can't read, nor did you read RichD's OP where he said the
thing I quoted. Which is why they call it a quote.
> What you said was this: "An isolated body can't shift it's center of
> gravity."http://groups.google.com/group/rec.martial-arts/msg/c161ee4a56a8ccae
True or false?
> Wrong again. RichD said that an isolated body cannot generate net
> momentum. Do you see the difference?
Yes, I said the same thing in different words, and you freaked out.
Quite common, actually.
> Hell, I'm laughing at you now.
Laughing at nothing again? That might have something to do with your
mental retardation.
-
herbzet
Appledog wrote:
> herbzet wrote:
> > Appledog wrote:
> > > Neil Gendzwill wrote:
> >
> > > > I recall an old article in Scientific American from 1980 called
> > > > "The Physics of Somersaulting and Twisting". It described how
> > > > divers for example could start their body twisting without an
> > > > initial moment and nothing to push off of. Not available online but
> > > > I'm sure you could get it through the library - google search reveals
> > > > a lot of references to the article.
> >
> > > I might point out that a bird can also fly, and a fish can swim,
> > > without having anything to push off of.
> >
> > Lol, that's almost as good as "radius equals two pi squared"!
>
> Or even funnier, "It described how divers for example could start
> their body twisting without an initial moment and nothing to push off
> of."
>
> Boy, do you ever have egg on your face!
So, in reference to an article about "Somersaulting and Twisting",
you interpret "divers" as meaning underwater divers, rather than
springboard or platform divers. Because underwater divers somersault
and twist all the time.
God, you're right! How humiliating -- for *me*!
Worse than "radius equals two pi squared"!
I'm *mortified*!
So, um, what about the cat righting itself as it falls? No comment?
So how about this: You're floating peacefully in space, in free-fall,
outside the space station, wearing your space suit, of course. Perhaps
listening to a Bach organ fugue in your helmet headphones.
And you have cradled under your arm a hammer -- one of those Olympic
hammer-throwing hammers -- you know, a 16 pound (7.2 kg) iron ball at
the end of a three-foot chain.
Now you begin to swing that hammer around in a circle -- above your head,
or on your right side, or left side, or in front of you, in a clockwise
or counterclockwise direction, like a propeller on a plane.
Do you suppose you can induce a rotation in your bodily orientation,
wrt, say, the space station?
What if you didn't have an Olympic hammer, but had a big tail, like,
say, a cat does?
Or maybe if you just swing your legs around in a big circle? Or arms?
Or both?
Ever seen any trampolining?
Ever see a "diver" do a jackknife ... and end up in a stable head-down
orientaion?
Or ... a helicopter when the tail rotor stops working?
It spins.
> The funny part is that you even left the following tagged onto your
> post, as if you not only hadn't had the time to snip it, but read it
> as well:
Yes, that *was* hilarious!
> > > That would of
> > > course imply frictionless acceleration is possible. I hope I am not
> > > nitpicking too much here Neil, I am sure it looks like it shouldn't be
> > > possible what they're doing but there must be a real, simple,
> > > scientific, physical explanation for what is going on - just like
> > > there is for everything else in the martial arts. That's always been
> > > the case with everything I've seen so far so I doubt it would be any
> > > different for anything else.
>
> Anyways. Have a nice life, idiot.
Have a nice day, sunshine! :)
--
hz
Appledog
>
> > > Lol, that's almost as good as "radius equals two pi squared"!
>
> > Or even funnier, "It described how divers for example could start
> > their body twisting without an initial moment and nothing to push off
> > of."
>
> > Boy, do you ever have egg on your face!
>
> So, in reference to an article about "Somersaulting and Twisting",
> you interpret "divers" as meaning underwater divers, rather than
> springboard or platform divers. Because underwater divers somersault
> and twist all the time.
>
> God, you're right! How humiliating -- for *me*!
>
> Worse than "radius equals two pi squared"!
>
> I'm *mortified*!
You should be. Because not only did androclese not get it, you
actually thought I was being serious. Or, possibly, you are just
looking for anything at all to try and pick on. It isn't working.
> So, um, what about the cat righting itself as it falls? No comment?
Lol, no, no comment. I wasn't really talking to you. You're almost a
complete waste of my time.
> So how about this: You're floating peacefully in space, in free-fall,
> outside the space station, wearing your space suit, of course. Perhaps
> listening to a Bach organ fugue in your helmet headphones.
Okay. Not that this has anything to do with anything in the first
place, but is it okay if I have some popcorn in a feeder?
> And you have cradled under your arm a hammer -- one of those Olympic
> hammer-throwing hammers -- you know, a 16 pound (7.2 kg) iron ball at
> the end of a three-foot chain.
Okay, sure. Given that ridiculous premise, let's see...
> Now you begin to swing that hammer around in a circle -- above your head,
> or on your right side, or left side, or in front of you, in a clockwise
> or counterclockwise direction, like a propeller on a plane.
Okay sure.
> Do you suppose you can induce a rotation in your bodily orientation,
> wrt, say, the space station?
It's interesting you would bring up conservation of angular momentum
as a means of propulsion but you will quickly find that regardless of
whatever movement you perform your center of gravity won't move. This
means you and the hammer. You need to be more careful; you have asked
if I can induce a rotation in my bodily orientation wrt (say) some
independant observer. The only true answer (yes) might be taken as
some sort of evidence I was wrong, until one realized that swinging
the hammer shared a single center of gravity betwee the two, which is
not the same thing as YOUR OWN center of gravity.
In essence, you have removed the idea of an isolated body by
introducing a 'hammer'. Was this yet another one of your pathetic
attempts to trick me, or was it simple ignorance?
> What if you didn't have an Olympic hammer, but had a big tail, like,
> say, a cat does?
>
> Or maybe if you just swing your legs around in a big circle? Or arms?
> Or both?
>
> Ever seen any trampolining?
>
> Ever see a "diver" do a jackknife ... and end up in a stable head-down
> orientaion?
>
> Or ... a helicopter when the tail rotor stops working?
Have you ever fucked yourself?
> It spins.
Yeah I know. Go try it. Go fuck yourself and see what happens.
HTH!
Shuurai
> > > Because you apparently missed it in RichD's message and knowing how
> > > much you know about science, I just wanted to point out the error so
> > > it didn't embarrass you further.
>
> > And so you decided to respond with an incorrect statement?
>
> If you can't understand sarcasm that isn't my problem.
Oh, so now it was sarcasm. Okay, Hal.
> > You know there was no need for me to mention an isolated body, so you
> > decided to mention an isolated body (within an incorrect statement) in
> > order to accomplish what?
>
> To show you that you were operating under a delusion posted in RichD's
> message. What the fuck is wrong with you that you will talk to RichD
> and accept his premise, which is "...an isolated body..." but you
> start arguing with me when I point out that both of you are wrong?
I didn't accept his premise of an isolated body; I moved past it
because it wasn't relevant to my response. And you didn't point out
anything - you issued an incorrect statement and are now trying to
pretend that you meant something else.
> > Admit it Ollie, the reason you "mentioned" it was because you wanted
> > to take part in a discussion that was beyond your abilities; which is
> > pretty sad considering this is high school level science. You failed
> > to notice that your statement made no sense, and now that it's been
> > pointed out to you that it was wrong, you're trying desperately to
> > pretend that someone else is to blame for you making an ass of
> > yourself.
>
> Dear lord. You're mentally retarded, aren't you?
You're really desperate for attention, aren't you?
> > That's not what I said, Ollie - nor is it what RichD said. It's what
> > YOU said, and it's incorrect.
>
> No, actually, it's what RichD said and what you took and ran with.
> DIdn't you see the quote I provided you? Oh, of course not.. you
> apparently can't read, nor did you read RichD's OP where he said the
> thing I quoted. Which is why they call it a quote.
You edited his quote, Ollie. What he said was that an isolated body
cannot generate net momentum. What you said was that an isolated body
can't shift it's center of gravity. Are you sure that YOU can read?
> > What you said was this: "An isolated body can't shift it's center of
> > gravity."http://groups.google.com/group/rec.martial-arts/msg/c161ee4a56a8ccae
>
> True or false?
True; that is what YOU said.
> > Wrong again. RichD said that an isolated body cannot generate net
> > momentum. Do you see the difference?
>
> Yes, I said the same thing in different words, and you freaked out.
> Quite common, actually.
No; you said something completely different. Even by your pitiful
standards, this attempt at weaseling out of your own words is pretty
fucking pathetic. By the way, just up above you claimed you were
being sarcastic. Why don't you take a moment and figure out ONE line
of bullshit to go with and then stick with that?
> > Hell, I'm laughing at you now.
>
> Laughing at nothing again? That might have something to do with your
> mental retardation.
I suppose you are about as close to nothing as any human being can be.
jbriggs444
You are correct. An isolated body cannot start rotating. And if it's
isolated there can't be anything to push off.
The trick is that a non-rigid body does not have to "rotate" in order
to change orientation. Nor does it need to acquire non-zero angular
momentum.
To go into agonizing detail...
Don your space suit. Step outside the space station. Take up
position 20 feet away from the airlock facing away from the space
station and standing erect.
Bend slightly forward. Your hips are now closer to the space station
and your head and feet are farther away.
Move your hips to the left, beginning a clockwise "hula hoop" motion.
Keep going. Your feet, your hips and your head are all moving in a
clockwise circuit (as viewed from above). They all have angular
momentum.
"But angular momentum is conserved!", you exclaim. Quite correct. It
is conserved. As your feet, your hips and your head are all moving in
circles clockwise, the orientation of your nose, your belly button and
your toes are all shifting in a counter-clockwise direction. The
angular momentum accounted for by the one motion precisely balances
the angular momentum accounted for by the other motion.
Keep up this pattern of motion until your nose points at the space
station.
Now stop. You will be bent over (forward, backward, to the side or at
some intermediate angle). Unbend so that you are once again erect.
Congratulations. You have changed orientation without ever having non-
zero angular momentum.
[This is essentially what a cat does to land on its feet. A cat is
flexible and can do it extremely quickly. Personal experimentation
reveals that a cat requires about 6 inches (~1/6 of a second) to
change orientation by 180 degrees]
Your "rotation rate" during this exercise is not well defined since
you were not a rigid body. You might choose to regard the orientation
of your nose as defining your rotation rate. Or you might choose to
regard the rotation of your hips as defining your rotation rate. Or
you might choose to compute angular momentum divided by moment of
inertia. But you'll get three different answers. "Rotation of a
rigid body" is a poor way to think about this kind of situation.
"Changing orientation" challenges fewer intuitions.
Appledog
>
> Congratulations. You have changed orientation without ever having non-
> zero angular momentum.
Agreed, but that was never the issue. The issue was if the center of
gravity could be moved, and you will find that in this example it has
not yet moved.
Interesting example tho :)
-
Appledog
>
> I didn't accept his premise of an isolated body; I moved past it
> because it wasn't relevant to my response. And you didn't point out
> anything - you issued an incorrect statement and are now trying to
> pretend that you meant something else.
Oh, now you've moved past it? Okay hal.
> > No, actually, it's what RichD said and what you took and ran with.
> > DIdn't you see the quote I provided you? Oh, of course not.. you
> > apparently can't read, nor did you read RichD's OP where he said the
> > thing I quoted. Which is why they call it a quote.
>
> You edited his quote, Ollie.
You're lying.
-
Sam the Bam
> The trick is that a non-rigid body does not have to "rotate" in order
> to change orientation. Nor does it need to acquire non-zero angular
> momentum.
>
> To go into agonizing detail...
>
> Don your space suit. Step outside the space station. Take up
> position 20 feet away from the airlock facing away from the space
> station and standing erect.
>
> Bend slightly forward. Your hips are now closer to the space station
> and your head and feet are farther away.
>
> Move your hips to the left, beginning a clockwise "hula hoop" motion.
> Keep going. Your feet, your hips and your head are all moving in a
> clockwise circuit (as viewed from above). They all have angular
> momentum.
>
> circles clockwise, the orientation of your nose, your belly
> button and your toes are all shifting in a counter-clockwise
> direction. The angular momentum accounted for by the
> one motion precisely balances
> the angular momentum accounted for by the other motion.
Your head moves cw, while your nose moves ccw?
Dude, u rool....
Sam
herbzet
Appledog wrote:
> herbzet wrote:
> >
> > > > Lol, that's almost as good as "radius equals two pi squared"!
> >
> > > Or even funnier, "It described how divers for example could start
> > > their body twisting without an initial moment and nothing to push off
> > > of."
> >
> > > Boy, do you ever have egg on your face!
> >
> > So, in reference to an article about "Somersaulting and Twisting",
> > you interpret "divers" as meaning underwater divers, rather than
> > springboard or platform divers. Because underwater divers somersault
> > and twist all the time.
> >
> > God, you're right! How humiliating -- for *me*!
> >
> > Worse than "radius equals two pi squared"!
> >
> > I'm *mortified*!
>
> You should be. Because not only did androclese not get it, you
> actually thought I was being serious.
Oh, the "I was joking" cop-out again. Like, "I'm posting another
the-sky-is-falling scenario, this time about armed revolution in
America this winter, but I'm just joking, ha-ha-ha, now aren't you
stupid for not getting that I'm joking?"
Trying to play off your idiocy as intentional joking --
yeah, right, no one gets your sophisticated humor; you're just
too slick for everyone here. It's amazing, isn't it, how no one
can see you when you have your head planted firmly up your ass?
Which explains the shit-eating grin: "Heh-heh, I'm just joking, see?"
> Or, possibly, you are just
> looking for anything at all to try and pick on. It isn't working.
>
> > So, um, what about the cat righting itself as it falls? No comment?
>
> Lol, no, no comment. I wasn't really talking to you. You're almost a
> complete waste of my time.
>
> > So how about this: You're floating peacefully in space, in free-fall,
> > outside the space station, wearing your space suit, of course. Perhaps
> > listening to a Bach organ fugue in your helmet headphones.
>
> Okay. Not that this has anything to do with anything in the first
> place, but is it okay if I have some popcorn in a feeder?
>
> > And you have cradled under your arm a hammer -- one of those Olympic
> > hammer-throwing hammers -- you know, a 16 pound (7.2 kg) iron ball at
> > the end of a three-foot chain.
>
> Okay, sure. Given that ridiculous premise, let's see...
>
> > Now you begin to swing that hammer around in a circle -- above your head,
> > or on your right side, or left side, or in front of you, in a clockwise
> > or counterclockwise direction, like a propeller on a plane.
>
> Okay sure.
>
> > Do you suppose you can induce a rotation in your bodily orientation,
> > wrt, say, the space station?
>
> It's interesting you would bring up conservation of angular momentum
> as a means of propulsion
I didn't say anything about "propulsion", nor did anyone else but you --
but nice try at perception management again.
> but you will quickly find that regardless of
> whatever movement you perform your center of gravity won't move.
I never asserted that it did, since that's not at issue. That's *your*
strawman issue, with which you try to distract attention from your error.
All you had to say is "Oh, you meant *platform* divers doing gymnastics,
not underwater divers. Oops, my mistake." But now you're stuck trying
to defend your simple misunderstanding by inventing strawmen arguments,
making yourself look like a retard (again) instead of a grown-up mature
man who can say "Oops, I misunderstood what you said".
But you're fully invested in your idiocy now: you're stuck with inventing
ever more preposterous arguments, aren't you? This is easy for me now; I
can just sit back and let you make an ever-bigger fool of yourself -- it's
like shooting fish in a barrel:
> This
> means you and the hammer. You need to be more careful; you have asked
> if I can induce a rotation in my bodily orientation wrt (say) some
> independant observer. The only true answer (yes) might be taken as
> some sort of evidence I was wrong,
Yes, you *were* wrong, when you said "I don't for one moment believe they
can start rotating without having anything to push off of." That's a
direct, cut-and-paste quote from you, so you can bag your usual accusation
of me lying about what you said.
And you were wrong -- just wrong. Try to be grown-up about it.
Alternatively, you could just go and beat some more "bad" kids in
your class, so you can feel better about yourself. Like you're a
big grown up man and all.
> until one realized that swinging
> the hammer shared a single center of gravity betwee the two, which is
> not the same thing as YOUR OWN center of gravity.
Not necessarily true: one can arrange to have one's own center of
gravity coincide with the COG of the self-hammer system.
But though your remark is correct in the case of whirling the hammer
around in a plane that does not include YOUR center-of-gravity, it is,
of course, an utterly irrelevant remark to the point at issue.
Um, you *do* understand the point at issue, right? :)
Hint: it has something to do with the physics of sit-ups.
But don't let me stop you from sqirting more ink like a frightened
squid. You're all in now!
> In essence, you have removed the idea of an isolated body by
> introducing a 'hammer'.
Lol -- really clueless, appledork. I'm sorry, but I'm afraid you'll
just have to take my word for that, since you're really clueless.
> Was this yet another one of your pathetic
> attempts to trick me, or was it simple ignorance?
Why do you insist on talking about physics?
Really, 'dork, it just makes you look stupid, I mean, stupider.
> > What if you didn't have an Olympic hammer, but had a big tail, like,
> > say, a cat does?
> >
> > Or maybe if you just swing your legs around in a big circle? Or arms?
> > Or both?
> >
> > Ever seen any trampolining?
> >
> > Ever see a "diver" do a jackknife ... and end up in a stable head-down
> > orientaion?
> >
> > Or ... a helicopter when the tail rotor stops working?
>
> Have you ever fucked yourself?
No, but don't think I haven't tried.
> > It spins.
>
> Yeah I know. Go try it. Go fuck yourself and see what happens.
I love it when you get pissed off. That's when I know -- I gotcha!
Heh-heh-heh!
Have a nice day, 'dork! :)
--
hz
Androcles
"herbzet" <her...@gmail.com> wrote in message
news:4B208DAB...@gmail.com...
Easy, isn't it? The trouble is there are so many fish in the barrel
(just like him) that it gets boring; then you use a grenade and
throw in a worm on a hook for the survivor.
"Some men, reasoning preposterously, first establish some conclusion
in their minds which, either because of its being their own or because
of their having received it from some person who has their entire
confidence, impresses them so deeply that one finds it impossible
ever to get it out of their heads." -- Galileo Galilei.
herbzet
Androcles wrote:
> Easy, isn't it? The trouble is there are so many fish in the barrel
> (just like him) that it gets boring; then you use a grenade and
> throw in a worm on a hook for the survivor.
>
> "Some men, reasoning preposterously, first establish some conclusion
> in their minds which, either because of its being their own or because
> of their having received it from some person who has their entire
> confidence, impresses them so deeply that one finds it impossible
> ever to get it out of their heads." -- Galileo Galilei.
Thanks for your support, but please -- don't take my posts to
AppallingDork as an endorsement of your position on -- well,
anything.
--
hz
Androcles
You'll have to beg harder than that. It's amazing, isn't it, how no one
can see you when you have your head planted firmly up your arse?
jbriggs444
> On Dec 9, jbriggs444 <jbriggs...@gmail.com> wrote:
> > As your feet, your hips and your head are all moving in
> > circles clockwise, the orientation of your nose, your belly
> > button and your toes are all shifting in a counter-clockwise
> > direction. The angular momentum accounted for by the
> > one motion precisely balances
> > the angular momentum accounted for by the other motion.
>
> Your head moves cw, while your nose moves ccw?
> Dude, u rool...
Close, but no cigar. Read for comprehension next time and pay
attention to word choice.
Another set of words that could have been brought to bear would
include "rotate" and "revolve". And, perhaps,
"retrograde". An example would be Venus.
Appledog
what a long message.. i admit skimmed it but I didn't see anything
worthwhile...
-
Appledog
Sorry didn't see this until just now.
I already told you, it was convex. Twice. Actually this is the third
time. Did you need a run down of the hula hoop experiment again or do
you agree that at some point Pi will be exactly three?
-