Question About Sports And Gravity
Josh L
I am wondering if there are comparatively minute fluctuations in
gravitational pull on athletes' bodies (and the various tools of their
sports), and to what extent these fluctuations might affect the
outcome of events, and whether research has been done into this.
In Track & Field, the effect of air assistance or resistance is
acknowledged strongly enough such that the air flow is measured during
or around a race, and if it is too strong, then a wind-aided time
cannot count as a record.
Also in Track & Field, I don't know if there was an adjustment of the
rules after the Mexico City Olympics in acknowledgement that, in some
events, the thin air may have helped accomplish world records that
were a bit more statistically "outliers" than was expected at that
time (Bob Beamon's Long Jump, the strong world records in the Men's
400 meters and 200 meters, etc.).
So, with these thoughts in mind, I started wondering if the outcome of
some events might be affected by the moderate ebb and flow of
gravitational forces, such as are related to the Moon and perhaps (to
a lesser extent) the sun or even localized to certain parts of the
globe. While the changes in forces may be comparatively minute, so
too are the fractions of seconds that determine world records and
winners and losers. Maybe an historical statistical study could be
easily done, looking at performance versus the tides or versus some
local empirical measurement of gravitational forces. Are such
measurements taken? Perhaps not. Well, we know something of the
tides, so I guess that could be a proxy.
jl
tadchem
google "channel swimming"
Tom Davidson
Richmond, VA
David Williams
-> some events might be affected by the moderate ebb and flow of
-> gravitational forces, such as are related to the Moon and perhaps (to
-> a lesser extent) the sun or even localized to certain parts of the
-> globe. While the changes in forces may be comparatively minute, so
-> too are the fractions of seconds that determine world records and
-> winners and losers. Maybe an historical statistical study could be
-> easily done, looking at performance versus the tides or versus some
-> local empirical measurement of gravitational forces. Are such
-> measurements taken? Perhaps not. Well, we know something of the
-> tides, so I guess that could be a proxy.
-> jl
The moon's mass is only about 1/80 of the earth's mass, and the centre
of the moon is about 60 times further away from the earth's surface than
the centre of the earth. So the earth's gravity, at its surface, is
about 80 x 60 x 60 or nearly 300,000 times stronger than the moon's. I
don't think a variation of about three parts per million in
gravitational pull is going to make a measurable difference to athletic
performance.
On the other hand, there are variations much greater than that from
place to place on the earth's surface, mainly due to altitude. A place
that's 2 km above sea level is about 3e-4 earth-radii further from the
earth's centre than a place at sea level, so the pull of gravity is
about 6e-4 g less than at sea level. Thet's 300 times greater than the
effect of the moon. Could that have an appreciable effect on athletic
performances? Maybe.
dow
Josh L
>of the moon is about 60 times further away from the earth's surface than
>the centre of the earth. So the earth's gravity, at its surface, is
>about 80 x 60 x 60 or nearly 300,000 times stronger than the moon's. I
>don't think a variation of about three parts per million in
>gravitational pull is going to make a measurable difference to athletic
>performance.
>
>On the other hand, there are variations much greater than that from
>place to place on the earth's surface, mainly due to altitude. A place
>that's 2 km above sea level is about 3e-4 earth-radii further from the
>earth's centre than a place at sea level, so the pull of gravity is
>about 6e-4 g less than at sea level. Thet's 300 times greater than the
>effect of the moon. Could that have an appreciable effect on athletic
>performances? Maybe.
>
> dow
Yes. After I posted my question I realized that I'd left out an
important part which is that any trend after the 1968 Olympics to
recognize that performing at altitude may have influenced the outcomes
of events is a trend that was taking into account both wind resistance
and gravity. Both are reduced at altitude, as is the amount of
available air for endurance event participants to breathe.
So, I was accustomed to thinking of the outfall of the '68 Olympics as
an air resistance thing, but I guess it would also be a recognition of
gravitational efffect upon performance?
I've been taught most of my life that the tides are, for the most
part, a result of the interaction of the moon with the Earth, so even
granting your equations, the effect of the Earth-moon interaction at
sea level seems to be palpable for bodies of water, and perhaps also
palpable for elite athletic competition. Now, it may not be a simple
matter of the Moon's pull so much as that plus some aspects of the
Earth's rotation and orbit that are harder to understand?
David Williams
-> part, a result of the interaction of the moon with the Earth, so even
-> granting your equations, the effect of the Earth-moon interaction at
-> sea level seems to be palpable for bodies of water, and perhaps also
-> palpable for elite athletic competition. Now, it may not be a simple
-> matter of the Moon's pull so much as that plus some aspects of the
-> Earth's rotation and orbit that are harder to understand?
Along most coasts, tides are quite small, less than a metre high. In
many places they are too small to be easily noticeable. Only in a few
places where there is an accidental resonance between the "sloshing"
frequency of the water in a semi-confined space and the roughly
twice-daily frequency of the tides does the amplitude become high.
Tides are produced by the interaction of (principally) the moon's
gravity with oceans of water that are thousands of kilometres in size.
Smaller bodies of water such as the Mediterranean Sea or Lake Superior
do not have perceptible tides. Even the largest athletes do not have
bodies large enough to be measurably affected.
dow
Josh L
the effect this might have on sports performance.
jl
David Williams
-> the effect this might have on sports performance.
Well, in an extreme case, altitude might alter the weight (but not the
mass) of an athlete by about 0.1 percent. So suppose in the long-jump
the distance a jumper can go is inversely proportional to the force of
gravity pulling him down, then if he can jump about 5 metres, he might
go 5 millimetres further at high altitude than at sea level, from this
cause. Also, there would be less air resistance slowing him down, so he
should be able to jump further still.
5 mm is a significant distance in this sport.
While we're on this line of thought, have you ever considered the
effect the earth's rotation has on the trajectory of something like a
golf ball? The Coriolis effect pushes it sideways, in opposite
directions in the northern and southern hemispheres. When a golfer gets
a "hole in one", he must (purely by accident) have compensated for the
sideways force on the ball, which would otherwise have moved it several
centimetres from the hole.
dow
Ralph
difference of 5 mm average, you'd have to be at an altitude where you
couldn't breathe.
There are studies going on, though, and gravity is a hot topic in physics.
The earths spin is also negligable. All the objects, including the air are
also in motion.
Why pick on such esoteric straws? Deal with the reality, and measureable
results.
The larger, and measureable effects are from the air, and 99% will be the
skill and attitude of the athlete.
More dense air in cold pressure areas, and at sea level will affect
performance two ways.
You get more oxygen, but have more air to push through.
At higher altitudes and lower pressure, that is reversed in still air.
Moving air adds its own force.
Don't blame the air, unless you're willing to stop using it.
"David Williams" <david.w...@bayman.org> wrote in message
news:1219113535.8...@bayman.org...
David Williams
-> difference of 5 mm average, you'd have to be at an altitude where you
-> couldn't breathe.
You'd have to be about 3 km above sea level. Sure, that's high, but not
high enough to prevent breathing. People live that high in places. It's
only about one-third as high as Everest.
dow
Ralph
diameter of just short of 8000 miles?
I'd like to see the math.
Yes, even at 3 miles altitude, it is *possible* to breathe, and with
conditioning, even live. People in Chile have developed their bodies in
these conditions.
Astronomers regularly have observatories at these altitudes.
Above that, and especially on Everest, where more than a third of the people
die in the attempt, oxygen is carried in tanks.
Athletics in those conditions is dangerous.
"David Williams" <david.w...@bayman.org> wrote in message
news:1219189335.8...@bayman.org...
David Williams
-> diameter of just short of 8000 miles?
-> I'd like to see the math.
I've already posted it, but here it is again.
The earth's radius is 6000 km (to one dignificant digit). 3 km is
therefore 1/2000 of the radius. The force of gravity is inversely
proportional to the *square* of the distance from the earth's centre,
so changing this distance by 1 part in 2000 will cause a change in
gravity by 1 part in 1000. In the long jump, the distance jumped is
proportional to the time in the air which is omversely proportional to
the force of gravity pulling the jumper down. So if a jumper can jump
about 5 metres, which good jumpers can, then at an altitude of 3 km he
should be able to jump about 5 mm further than at sea level, from this
cause.
-> Above that, and especially on Everest, where more than a third of the people
-> die in the attempt, oxygen is carried in tanks.
Not always. Nowadays a lot of climbers get to the summit just breathing
the ambient air.
dow
Ralph
error in estimation. The earths mass is grossly estimated at 5.97 x 10^24
kg, (note the error in the 10^21 kg range) and the diameter, depending on
how you take it, about 7926 miles. (error in miles) How do you justify an
answer in mm. or the weight of an athlete or his equipment?
'Wiki' has an article that I skimmed, and shows a difference in wieght of
.28% with over 8000 m in height. I doubt any measurable difference in an
athletes performance could be measured that finely.
http://en.wikipedia.org/wiki/Earth's_gravity
"David Williams" <david.w...@bayman.org> wrote in message
news:1219246633.8...@bayman.org...
Ralph
"BBO" <az...@dod.no> wrote in message
news:n6SdndEitLT...@telenor.com...
> Ralph wrote:
>> Use some figures that make sense. Your answer is a small percentage of
>> your error in estimation. The earths mass is grossly estimated at 5.97 x
>> 10^24 kg, (note the error in the 10^21 kg range) and the diameter,
>> depending on how you take it, about 7926 miles. (error in miles) How do
>> you justify an answer in mm. or the weight of an athlete or his
>> equipment?
>
> Given a spherical cow of uniform density we easily see that....
>
> Read: In theory and working with exact numbers you can justify those kind
> of numbers. In reality - not possible, because we all know there is no
> such cow.
>
> --
> You can't be a rational person six days a week...and on one day of the
> week, go to a building, and think you're drinking the blood of a two
> thousand year old space god. -- Bill Maher
David Williams
and miles.
My estimate of a decrease of gravitational force, and therefore of the
weight of an athlete, of 0.1 percent per 3000 metres of height is close
to what you quote from Wiki, 0.28 percent for a height of 8000 metres.
Thanks for confirming my result.
There is nothing inaccurate in my calculation, or in the way I did it,
except that I slightly underestimated the distances that long jumpers
jump. In the Olympic Games a few days ago, the best jumpers were going
more than 6 metres. I estimated 5. So the increase in distance at a
height of 3000 metres would be more than 6 millimetres, compared with
at sea level. In the sport, distances are measured to the nearest
centimetre, so 6 millimetres would often change a measured result.
dow
-> Use some figures that make sense. Your answer is a small percentage of your
-> error in estimation. The earths mass is grossly estimated at 5.97 x 10^24
-> kg, (note the error in the 10^21 kg range) and the diameter, depending on
-> how you take it, about 7926 miles. (error in miles) How do you justify an
-> answer in mm. or the weight of an athlete or his equipment?
-> 'Wiki' has an article that I skimmed, and shows a difference in wieght of
-> ..28% with over 8000 m in height. I doubt any measurable difference in an
-> athletes performance could be measured that finely.
-> http://en.wikipedia.org/wiki/Earth's_gravity
-> "David Williams" <david.w...@bayman.org> wrote in message
-> news:1219246633.8...@bayman.org...
-> >-> ....to make a measureable difference in gravity, with the earths mass? -
-> >and
-> > -> diameter of just short of 8000 miles?
-> > -> I'd like to see the math.
-> >
-> > I've already posted it, but here it is again.
-> >
-> > The earth's radius is 6000 km (to one dignificant digit). 3 km is
-> > therefore 1/2000 of the radius. The force of gravity is inversely
-> > proportional to the *square* of the distance from the earth's centre,
-> > so changing this distance by 1 part in 2000 will cause a change in
-> > gravity by 1 part in 1000. In the long jump, the distance jumped is
-> > proportional to the time in the air which is omversely proportional to
-> > the force of gravity pulling the jumper down. So if a jumper can jump
-> > about 5 metres, which good jumpers can, then at an altitude of 3 km he
-> > should be able to jump about 5 mm further than at sea level, from this
-> > cause.
-> >
-> > -> Above that, and especially on Everest, where more than a third of the
-> > people
-> > -> die in the attempt, oxygen is carried in tanks.
-> >
-> > Not always. Nowadays a lot of climbers get to the summit just breathing
-> > the ambient air.
-> >
-> > dow
Ralph
numbers, but you'd pick on those, too. -doesn't matter. All the figures I
quoted are more accurate, and you still can't use them to make your math any
better.
Your guesses at numbers with errors on the order of (corrected) kilometers,
with answers in millimeters, are the nonsense here.
Math can't be accurate unless the answer is greater than (you don't seem to
comprehend this) the error in the original numbers.
Since your answer is orders of magnitude LESS than your errors in guessed-at
figures, your original statements and math are invalid.
The math from Wiki gives estimates for a model of gravity for a planet with
ideal condition of even density, and all other factors the same. It's
stated in the article.
In that *theoretical* world, using your estimates, a .1% difference would
change the weight of a 100 kg. athete by 100 grams.
Had a sandwich lately? It weighs more.
Realistically, that's neglible. All the other factors, including the mood
of the athlete, the weather that day, and lots more I'm sure an actual
athlete could name better than I, would be more notable than any change in
gravity.
That's why gravity is such a hot topic in physics. It's only recently that
equipment has been designed to work on such small differences. -on the
order of 10^-20 g.
Go for any numbers you make up and believe. I'll stick with the measured
results.
Have fun.
"David Williams" <david.w...@bayman.org> wrote in message
news:1219592763.8...@bayman.org...
David Williams
difficult. I showed a calculation, so simple that it can be done in the
head, that showed that, *from the effect of altitude on gravity*, a
long jumper wouold be able to jump the better part of a centimetre
further at an altitude of 3000 metres than at sea level, *all other
things being equal*. Since distances are measured to the nearest
centimetre, this would have a practical effect, making it easier to
break records at high altitudes,
You keep throwing out unnecessary numbers, such as the oblateness of
the earth. Certainly, there are other factors that affect how far an
athlete can jump, most significantly the wind, and latitude would be
one of these factors too. But my calculation was specifically about the
effect of altitude. Everything else is irrelevant.
Keep It Simple, Stupid.
If you want to argue that athletic records are meaningless because of
all the other factors, besides an athlete's ability, that can affect
results, then I would agree that you have a point. But if that's what
you mean, then that's what you should say.
dow
-> The units are irrelavent, and easily converted. I could supply specific
-> numbers, but you'd pick on those, too. -doesn't matter. All the figures I
-> quoted are more accurate, and you still can't use them to make your math any
-> better.
-> Your guesses at numbers with errors on the order of (corrected) kilometers,
-> with answers in millimeters, are the nonsense here.
-> Math can't be accurate unless the answer is greater than (you don't seem to
-> comprehend this) the error in the original numbers.
-> Since your answer is orders of magnitude LESS than your errors in guessed-at
-> figures, your original statements and math are invalid.
-> The math from Wiki gives estimates for a model of gravity for a planet with
-> ideal condition of even density, and all other factors the same. It's
-> stated in the article.
-> In that *theoretical* world, using your estimates, a .1% difference would
-> change the weight of a 100 kg. athete by 100 grams.
-> Had a sandwich lately? It weighs more.
-> Realistically, that's neglible. All the other factors, including the mood
-> of the athlete, the weather that day, and lots more I'm sure an actual
-> athlete could name better than I, would be more notable than any change in
-> gravity.
-> That's why gravity is such a hot topic in physics. It's only recently that
-> equipment has been designed to work on such small differences. -on the
-> order of 10^-20 g.
-> Go for any numbers you make up and believe. I'll stick with the measured
-> results.
-> Have fun.
-> news:1219592763.8...@bayman.org...
-> > My figures make more sense than yours, with your mixture of kilograms
-> > and miles.
-> >
-> > My estimate of a decrease of gravitational force, and therefore of the
-> > weight of an athlete, of 0.1 percent per 3000 metres of height is close
-> > to what you quote from Wiki, 0.28 percent for a height of 8000 metres.
-> > Thanks for confirming my result.
-> >
-> > There is nothing inaccurate in my calculation, or in the way I did it,
-> > except that I slightly underestimated the distances that long jumpers
-> > jump. In the Olympic Games a few days ago, the best jumpers were going
-> > more than 6 metres. I estimated 5. So the increase in distance at a
-> > height of 3000 metres would be more than 6 millimetres, compared with
-> > at sea level. In the sport, distances are measured to the nearest
-> > centimetre, so 6 millimetres would often change a measured result.
-> >
-> > dow
-> >
-> > -> Use some figures that make sense. Your answer is a small percentage of
-> > your
-> > -> error in estimation. The earths mass is grossly estimated at 5.97 x
-> > 10^24
-> > -> kg, (note the error in the 10^21 kg range) and the diameter, depending
-> > on
-> > -> how you take it, about 7926 miles. (error in miles) How do you justify
-> > an
-> > -> answer in mm. or the weight of an athlete or his equipment?
-> >
-> > -> 'Wiki' has an article that I skimmed, and shows a difference in wieght
-> > of
-> > -> ..28% with over 8000 m in height. I doubt any measurable difference in
-> > an
-> > -> athletes performance could be measured that finely.
-> >
-> > -> http://en.wikipedia.org/wiki/Earth's_gravity
-> >
-> > -> "David Williams" <david.w...@bayman.org> wrote in message
-> > -> news:1219246633.8...@bayman.org...
-> > -> >-> ....to make a measureable difference in gravity, with the earths
-> > mass? -
-> > -> >and
-> > -> > -> diameter of just short of 8000 miles?
-> > -> > -> I'd like to see the math.
-> > -> > I've already posted it, but here it is again.
-> > -> >
-> > -> > The earth's radius is 6000 km (to one dignificant digit). 3 km is
-> > -> > proportional to the *square* of the distance from the earth's centre,
-> > -> > so changing this distance by 1 part in 2000 will cause a change in
-> > -> > gravity by 1 part in 1000. In the long jump, the distance jumped is
-> > -> > proportional to the time in the air which is inversely proportional
-> > to
-> > -> > the force of gravity pulling the jumper down. So if a jumper can jump
-> > -> > about 5 metres, which good jumpers can, then at an altitude of 3 km
-> > he
-> > -> > should be able to jump about 5 mm further than at sea level, from
-> > this
-> > -> > cause.
-> > -> > -> Above that, and especially on Everest, where more than a third of
-> > -> > people
-> > -> > -> die in the attempt, oxygen is carried in tanks.
-> > -> > Not always. Nowadays a lot of climbers get to the summit just
-> > -> > the ambient air.
-> > -> >
-> > -> > dow
Ralph
Your denial of math logic, and the concept of gravity without using the most
basic part of it, are flawed.
The insignifcant values that you plug into your imaginary formulations give
you numbers that you're welcome to believe, done in your head, and
therefore, imagined true. If that's what you believe, you're welcome to
believe that an athletes mass is more important to gravity than the mass of
the earth.
This is a fairly simple concept, even in Newtonian gravity.
Result error based on inaccurate input is also fairly basic.
Keeping it simple: Garbage in, garbage out.
Your guesstimates seem to be increasing with your posts, so there's no
consistancy there.
This seems to be a philosophical tirade, since there are so many other
factors, and all other things would not be equal.
What I'm saying is that gravity is neither a measureable effect, or even one
that needs consideration in athletics.
I will never deny that athletic records are meaningless, so don't go putting
more words in my honour.
Actually, go ahead. It's fun to read and pass along to friends.
I'll say, not what you're trying to goad me into, but what I've backed up.
Simple, stupid.
"David Williams" <david.w...@bayman.org> wrote in message
news:1219679784.8...@bayman.org...
Ken S. Tucker
> OK, for you: simple.
>
> Your denial of math logic, and the concept of gravity without using the most
> basic part of it, are flawed.
> The insignifcant values that you plug into your imaginary formulations give
> you numbers that you're welcome to believe, done in your head, and
> therefore, imagined true. If that's what you believe, you're welcome to
> believe that an athletes mass is more important to gravity than the mass of
> the earth.
> This is a fairly simple concept, even in Newtonian gravity.
>
> Result error based on inaccurate input is also fairly basic.
> Keeping it simple: Garbage in, garbage out.
>
> Your guesstimates seem to be increasing with your posts, so there's no
> consistancy there.
>
> This seems to be a philosophical tirade, since there are so many other
> factors, and all other things would not be equal.
> What I'm saying is that gravity is neither a measureable effect, or even one
> that needs consideration in athletics.
>
> I will never deny that athletic records are meaningless, so don't go putting
> more words in my honour.
> Actually, go ahead. It's fun to read and pass along to friends.
> I'll say, not what you're trying to goad me into, but what I've backed up.
> Simple, stupid.
So is that why high jumpers and pole-vaulters do
better when the moon is full, because of tidal force?
Ken
PS:Usually Daves "guestimates" are as accurate
as my calculator!
"all other things being equal" is a partial derivative.
Ralph
Go to the head of the class!
"Ken S. Tucker" <dyna...@vianet.on.ca> wrote in message
news:2ba8f80c-ac3c-4626...@z6g2000pre.googlegroups.com...
Ken S. Tucker
On Aug 25, 3:33 pm, "Ralph" <aj...@ncf.ca> wrote:
> Very good.
> Go to the head of the class!
Thanks:-). Your discussion got to me to thinking
if we launched a rocket (all other things being equal)
at high tide (full or new moon) if less propellant
would be required to achieve the same orbit if we
launched at neap tide.
I'm hoping for a simple answer, otherwise I'll need to
enter the Riemann Christoffel "tidal tensor", R_abcd
into the geodesic.
Regards
Ken
> "Ken S. Tucker" <dynam...@vianet.on.ca> wrote in messagenews:2ba8f80c-ac3c-4626...@z6g2000pre.googlegroups.com...
David Williams
If you think that calculations done as you think they should be done
will produce a conclusion different from mine, then let's see them. Put
up, or shut up.
I don't include the earth's mass in my calculation because I can see in
advance it will cancel out. In order to calculate a jumper's takeoff
velocity, I will have to start with the distance he can jump, since
that's a measured quantity, and work backward, using the earth's mass.
Then I'll work forward again, using the mass again, and it will simply
cancel out! So I might as well just use the distance a jumper can
jump in the calculation, and not worry about the earth's mass.
But I guess you're too stupid to see that.
Ken Tucker has known me for decades. If he criticizes my logic, I take
the criticism seriously. But criticism from you is clearly of no
consequence.
dow
Ken S. Tucker
On Aug 25, 5:09 pm, david.willi...@bayman.org (David Williams) wrote:
> You're revealing yourself as an idiot.
>
> If you think that calculations done as you think they should be done
> will produce a conclusion different from mine, then let's see them. Put
> up, or shut up.
>
> I don't include the earth's mass in my calculation because I can see in
> advance it will cancel out. In order to calculate a jumper's takeoff
> velocity, I will have to start with the distance he can jump, since
> that's a measured quantity, and work backward, using the earth's mass.
> Then I'll work forward again, using the mass again, and it will simply
> cancel out! So I might as well just use the distance a jumper can
> jump in the calculation, and not worry about the earth's mass.
While I lurked this discussion, I was replaying
(in my mind) the video of the Apollo astronauts
on the moon, but that could be a "red herring".
> Ken Tucker has known me for decades.
Dave, you are too complex to really know,
but I'll try for a few more decades ;-).
> If he criticizes my logic, I take the criticism seriously.
LOL, you never did before, but really, the equation is
acceleration = GM/r, with a minor variance on "r",
should I Rubber Bible G,M,r and dr ?
> dow
Regards
Ken
Ralph
I was descending to a level of name-calling I didn't like, (but the source
shows) and no amount of logic can change that. (or any fantasy)
I'll leave cancelling the earths gravity to the source that brought it into
the subject.
Maybe I'll go watch a tide.
Thanks again,
"Ken S. Tucker" <dyna...@vianet.on.ca> wrote in message
news:e0c4418d-c9d0-41da...@t1g2000pra.googlegroups.com...
David Williams
-> Go to the head of the class!
-> "Ken S. Tucker" <dyna...@vianet.on.ca> wrote in message
....
-> > So is that why high jumpers and pole-vaulters do
-> > better when the moon is full, because of tidal force?
-> > Ken
-> > PS:Usually Daves "guestimates" are as accurate
-> > as my calculator!
-> > "all other things being equal" is a partial derivative.
So you're praising Ken for saying that my "guesstimates" are often very
good. Yet you seem to think the opposite.
Consistent you're not.
dow
David Williams
-> if we launched a rocket (all other things being equal)
-> at high tide (full or new moon) if less propellant
-> would be required to achieve the same orbit if we
-> launched at neap tide.
-> I'm hoping for a simple answer, otherwise I'll need to
-> enter the Riemann Christoffel "tidal tensor", R_abcd
-> into the geodesic.
-> Regards
-> Ken
My first guess is that it would be better (require less fuel) to have
the spacecraft travel to the moon at approximately new moon than at
other times of the month. Full moon would be the worst time. The
rotating vector of the sun's gravity (rotating because of the earth's
orbital motion) would add momentum to the craft at new moon and remove
it at full moon - I think. Both new and full moon are spring tide
situations, so the situation doesn't match the tides.
To be sure of this, I think a simulation should be done. I know you
already have most if not all of the necessary software, so you should
be the person to do it.
dow
Ken S. Tucker
On Aug 26, 6:46 am, "Ralph" <aj...@ncf.ca> wrote:
> Thanks Ken,
> I was descending to a level of name-calling I didn't like, (but the source
> shows) and no amount of logic can change that. (or any fantasy)
It may not be a direct extrapolation of radius,
perhaps local density has an effect.
> I'll leave cancelling the earths gravity to the source that brought it into
> the subject.
> Maybe I'll go watch a tide.
Check out "sci.physics.foundations" , it's moderated.
Regards
Ken
David Williams
-> LOL, you never did before, but really, the equation is
-> acceleration = GM/r, with a minor variance on "r",
-> should I Rubber Bible G,M,r and dr ?
-> Regards
-> Ken
No need. If the athlete's takeoff velocity can be resolved into a
horizontal component, Vh, and a vertical component, Vv, then at landing
he will be going downward at Vv, so the total change in velocity is
2Vv. The time this will take is 2Vv/g, so the distance he will travel
is 2.Vh.Vv/g. As you say, g=GM.r^2, so the distance the jumper travels
is 2.Vh.Vv.r^2/(GM). If the value of r changes from r1 to r2, then the
two distances the athlete jumps are:
d1 = 2.Vh.Vv.r1^2/(GM)
d2 = 2.Vh.Vv.r2^2/(GM)
So d2/d1 = (r2/r1)^2
Behold! The V's, G, and M have cancelled out! I could see that coming.
The twit obviously couldn't.
So if r2/r1 = 1.0005, which will be true if r1 = 6000 and r2 = 6003 (in
kilometres), then d2/d1 qill be 1.0005^2, which is almost precisely
1.001. If d1 = 6 (metres), d2 will be 6.006 metres. In other words, at
an altitude of 3000 metres, a good long-jumper who can jump 6 metres at
sea level will be able to jump 6 millimetres further. Since distances
are measure to the nearest centimetre, his jump distance will probably
be conted as 1 cm further than at sea level.
Ken, I'm sure this was obvious to you. Apparently at least one other
person here lacks your insight.
dow
Ken S. Tucker
> -> LOL, you never did before, but really, the equation is
> -> should I Rubber Bible G,M,r and dr ?
> -> Regards
> -> Ken
>
> No need. If the athlete's takeoff velocity can be resolved into a
> horizontal component, Vh, and a vertical component, Vv, then at landing
> he will be going downward at Vv, so the total change in velocity is
> 2Vv. The time this will take is 2Vv/g, so the distance he will travel
> is 2.Vh.Vv.r^2/(GM). If the value of r changes from r1 to r2, then the
> two distances the athlete jumps are:
>
> d1 = 2.Vh.Vv.r1^2/(GM)
> d2 = 2.Vh.Vv.r2^2/(GM)
>
> So d2/d1 = (r2/r1)^2
>
> Behold! The V's, G, and M have cancelled out! I could see that coming.
That's sweet the way it works out.
> So if r2/r1 = 1.0005, which will be true if r1 = 6000 and r2 = 6003 (in
> kilometres), then d2/d1 qill be 1.0005^2, which is almost precisely
> 1.001. If d1 = 6 (metres), d2 will be 6.006 metres. In other words, at
> an altitude of 3000 metres, a good long-jumper who can jump 6 metres at
> sea level will be able to jump 6 millimetres further. Since distances
> are measure to the nearest centimetre, his jump distance will probably
> be counted as 1 cm further than at sea level.
I think that same distance would ratio in Pole-Vault
as well (?). We can turn that (1.001) around to a
reduction of 1gm / Kg of the jumpers weight, so
an 80Kg athelete would jump 1/cm further for each
80 gms of weight loss.
The reason I'm curious is because (IIRC) the womens
long jump was 1 cm different, between 1st and 2nd.
If 80 gm's is true we're looking at shoe, bra and tampax
weight, and maybe even pooping before the jump :-).
> Ken, I'm sure this was obvious to you.
It's obvious now! 1 part in 1000 outputs 1 cm yeah(?).
Regards
Ken
David Williams
-> as well (?). We can turn that (1.001) around to a
-> reduction of 1gm / Kg of the jumpers weight, so
-> an 80Kg athelete would jump 1/cm further for each
-> 80 gms of weight loss.
Not if the loss is muscle.
dow
David Williams
-> Regards
-> Ken
In the marathon last week, plenty of athletes' times were within 1 part
in 1000 of each other.
In the final of the women's 100 metre hurdles, the favourite to win,
who was ahead at the time, just touched the second-last hurdle with her
foot. She stumbled and lost the lead. Quite likely, if her foot had
been 1 mm higher, i.e. about 1/1000 of the height of the hurdle, she
wouldn't have touched the hurdle and would have won the gold medal.
Such tiny differences can have huge effects.
dow
Peter Munn
message of Mon, 18 Aug 2008
>-> Thanks. I'll concentrate on the altitude and its effect on weight and
> -> the effect this might have on sports performance.
>
> Well, in an extreme case, altitude might alter the weight (but not the
> mass) of an athlete by about 0.1 percent.
Actually, latitude is the more important determinant of local gravity as
experienced in practice (that is net of centrifugal force) on Earth.
Plugging values into the relevant formula, I see that to obtain local
gravity as low as experienced at sea level at the equator, I would have
to ascend a mountain of 10,700m at my own latitude of 53 degrees. Of
course, no such mountain exists.
At 60 degrees 35' north, net gravity is 0.4% greater than at the
equator, so it's realistic to account for differences of 0.4% in local
gravity between athletic stadia.
So suppose in the long-jump
> the distance a jumper can go is inversely proportional to the force of
> gravity pulling him down,
Given equal initial vertical velocity, the time in the air is inversely
proportional to the _square root_ of the local gravity (this is related
to the units of local gravity being length divided by time _squared_).
So, with 0.1% lower gravity and take off speed being equal, you could
expect approximately 0.05% increase in distance; with 0.4% lower
gravity, approximately 0.2% increase.
then if he can jump about 5 metres, he might
> go 5 millimetres further at high altitude than at sea level, from this
> cause.
My upper end value of 0.2% would yield a 16mm increase to an 8m jump (a
jump at the lower end of male international standard). Horizontal jumps
are measured to the nearest 1cm, so this would be above the official
threshold of significance.
More striking, perhaps, the difference to a world record men's triple
jump (somewhat over 18m), would be 5cm or 6cm as measured. This is not
just theoretical, as Jonathan Edward's 1995 world record of 18.29m was
set in Goteborg in Sweden, a seaport 57.7 degrees North, so this may be
equivalent to 18.34m at the equator.
Also, there would be less air resistance slowing him down, so he
> should be able to jump further still.
I can confirm your assessment of the importance of air resistance, David
- it is generally recognised as being a major factor in athletic
performance. When decreased air resistance is due to following winds it
is officially recognised, and world records cannot be set in certain
track and field events unless there is a record of the wind speed and it
doesn't exceed 2 m/s in the direction of motion. I think empirical
analysis shows that wind assistance of 2 m/s is worth about 0.1s in a
world class men's 100m (so about 1%) - in any event, it can contribute
substantially more than gravity differences.
Since the 1968 Mexico City Olympics, there have often been debates in
athletics circles about whether similar status should be given to
performances that are "altitude assisted", because of the lesser air
resistance. Indeed, there was a time when some people kept unofficial
low-altitude world records for (principally) the men's 100m and men's
long jump, because the records set in 1968 at over 2000m altitude were
not being seriously challenged.
Beamon's long jump record was the most celebrated of these records, and
it had been set with the maximum allowable 2 m/s wind assistance as
well. Using a standard formula for fluid drag resistance, and assuming
air density at 75% of sea-level and that Beamon travelled at 10 m/s, I
calculated the combined reduced air resistance as equivalent to 3.5 m/s
wind assistance at sea level. So, there are strong grounds for arguing
that Beamon's performance had more environmental assistance than other
performances that were ineligible for accreditation as world records.
Beamon's record was broken in 1991, and afterwards the debate died down
about officially recognising "altitude assistance" for performances. As
to gravity differences affecting performances, I've never been aware of
it being debated in athletic circles.
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Ralph
so any real results would have to be checked to more accuracy than then
local variance.
Lists of G vs. location are available on the internet.
Much less math is needed if you check the facts.
"Peter Munn" <pmun...@pearce-neptune.demon.co.uk> wrote in message
news:5HphwCAR...@pearce-neptune.demon.co.uk...