Launch height of a cyclist in car accidents
bicycle_disciple
Traffico, a journal by the Directorate General of Traffic of the
Spanish Ministry Of The Interior claimed on the site :
"If a car traveling at 46.5 kph hits a cyclist, the force of impact
would be sufficient to send the cyclist up to the thirteenth floor of
a building."
I was puzzled. While I'm all for wearing helmets for protection, I
thought this claim might be bolder than it may seem in order to
advance their helmet agenda. There is no data to back it whatsoever,
so I did a small analysis using couple of real videos and some data.
If you're interested in reading it, the link is : http://tinyurl.com/9w34vp
Thoughts are welcome.
BD
John Forrest Tomlinson
<1.crazy...@gmail.com> wrote:
>"If a car traveling at 46.5 kph hits a cyclist, the force of impact
>would be sufficient to send the cyclist up to the thirteenth floor of
>a building."
http://www.youtube.com/watch?v=VGDwScgb_Y0
Sweeet!
Ecnerwal
<00bf1a1d-af67-4d40...@u14g2000yqg.googlegroups.com>,
bicycle_disciple <1.crazy...@gmail.com> wrote:
> I found this on a helmet advocacy website.
...
> Thoughts are welcome.
Having actually studied better (motorcycle) helmets some time ago,
hitting anything solid (resulting in an abrupt stop) at 46.5 kph/29 mph
will mostly just kill you dead (helmet or no helmet). Impact speed is
*roughly* equivalent to falling 24 feet/8m (stepping off the 3rd or 4th
floor, depending on building construction)
Helmets are primarily good for absorbing the impact of a fall from 6
feet (2 meters) - ie, when you fall down and hit the
ground/road/sidewalk as part of your crash, and then slide to a stop.
Much more than that and they don't help.
However, bad "science" in the name of helmet laws is a definite trend
that also turned up in my research. I'd go with the commentator that
suggested "total energy of the car" might be roughly equal to the
ludicrous figure posted - the total energy of the car will not be
imparted to the cyclist, of course.
I was and remain committed to wearing a helmet myself, but the only
actual effects of helmet laws (for motorcyclists) I documented was a
huge decrease in miles ridden per year. Fatalities per mile ridden
actually *increased*, but miles ridden decreased more, so fatalities per
year decreased. Why that is the case is a subject for debate without
possibility of an actual conclusion, but that it happened is well
documented and a fact.
--
Cats, coffee, chocolate...vices to live by
Philip Holman
"bicycle_disciple" <1.crazy...@gmail.com> wrote in message
news:00bf1a1d-af67-4d40...@u14g2000yqg.googlegroups.com...
Assume the car has a mass of 1500 kg and the bicycle/cyclist 100 kg. In
a conservative totally elastic collision (energy conserved), the
velocity of the cyclist after the collision (assume a stationary
cyclist) would be v2 = 2 (m1v1)/(m1+m2) = 2*1500*12.92/1600 = 24.225 m/s
If the kinetic energy of the bicycle/cyclist were totally converted to
potential energy, the height attained would be ........
h = 1/2v^2/g = 1/2*24.225^2/9.8 = 29.94 m
Assuming each story is 10 feet, this would be ~10 stories albeit under
the most ideal conditions. In reality it would be a lot less.
Phil H
Frank Krygowski
wrote:
> In article
> <00bf1a1d-af67-4d40-bf6d-e1f62f855...@u14g2000yqg.googlegroups.com>,
>
>
>
> bicycle_disciple <1.crazyboy.o...@gmail.com> wrote:
> > I found this on a helmet advocacy website.
> ...
> > Thoughts are welcome.
>
> Having actually studied better (motorcycle) helmets some time ago,
> hitting anything solid (resulting in an abrupt stop) at 46.5 kph/29 mph
> will mostly just kill you dead (helmet or no helmet). Impact speed is
> *roughly* equivalent to falling 24 feet/8m (stepping off the 3rd or 4th
> floor, depending on building construction)
>
> Helmets are primarily good for absorbing the impact of a fall from 6
> feet (2 meters) - ie, when you fall down and hit the
> ground/road/sidewalk as part of your crash, and then slide to a stop.
> Much more than that and they don't help.
More detail on that paragraph: Helmets are not even that good. The
certification test is a 2 meter drop. But the object dropped is a
magnesium model of a human head. It has no body attached, so the
body's inertia that may influence a real head impact is completely
ignored.
And the magnesium headform is rigid, while the human skull is not.
One effect this probably produces is that thinner, but stiffer
styrofoam gives suitable test results and allows super-ventilated,
super-light $150 helmets to just pass the test. But these are likely
more damaging to a real skull than thicker, softer helmets.
Finally, the certification test measures only linear acceleration of
the headform, not angular acceleration. It's pretty well known that
angular accelerations are much more damaging, but standard helmets
don't address them at all, and may even exacerbate them because of the
larger radius given to glancing blows.
> However, bad "science" in the name of helmet laws is a definite trend
> that also turned up in my research.
Absolutely. Helmets are sold using a combination of scare tactics
like those for stranger abductions of children, and "science" claims
like those of the diet industry. "Lose up to 85 pounds in one week!"
- Frank Krygowski
Tim McNamara
"Philip Holman" <pho...@wbhsi.net> wrote:
Yes, because a lot of that kinetic energy would be absorbed by
hysteresis in the jelly-like consistency of human tissues.
A helmet would likely be of no use in that scenario. The cyclist's
brain would get bounced off the inside of the skull from the instant
acceleration caused by the impact, and the rider could die from a brain
injury without his head hitting a thing. If that didn't kill him, the
internal thoracic and abdominal injuries would.
Tim McNamara
Ecnerwal <Lawren...@SOuthernVERmont.NyET> wrote:
The same phenomenon was reported when Australia passed a mandatory
helmet laws for bicyclists a few years back.
Tim McNamara
<1d2cf3ae-1ed9-4952...@w1g2000prm.googlegroups.com>,
Frank Krygowski <frkr...@gmail.com> wrote:
> On Jan 11, 10:13 am, Ecnerwal <LawrenceSM...@SOuthernVERmont.NyET>
> wrote:
> > However, bad "science" in the name of helmet laws is a definite
> > trend that also turned up in my research.
"No science" would be a better description. Some ER doc once gave an
off-the-cuff estimate that helmets would reduce cycling fatalities by
85% and it's been canon ever since.
> Absolutely. Helmets are sold using a combination of scare tactics
> like those for stranger abductions of children, and "science" claims
> like those of the diet industry. "Lose up to 85 pounds in one week!"
My favorite was the Bell helmet poster of a 10 year old sitting wearing
Air Jordans with the tag line "does your kid have $200 feet and a $20
head?" You're a baaaaaaaad parent if you don't buy our most expensive
helmet (which, as Frank pointed out, may provide *less* protection than
the cheap helmet).
Mike Jacoubowsky
>> like those for stranger abductions of children, and "science" claims
>> like those of the diet industry. "Lose up to 85 pounds in one week!"
But if you combined helmet use with losing 85 pounds, the end result
might be much better survivability in a collision, due to less mass
having to decelerate.
I don't understand the problem... looks like a no-brainer to me.
--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com
"Tim McNamara" <tim...@bitstream.net> wrote in message
news:timmcn-F6EF8E....@news.iphouse.com...
Leo Lichtman
"Philip Holman" wrote: (clip)In
> a conservative totally elastic collision (energy conserved), (clip)
^^^^^^^^^^^^^^^^^^^^
Not that I am taking these calculations seriously, but: a baseball hitting
a bat is close to a totally elastic collision. A cyclist hitting a car is
closer to a ball of putty hitting a tank. Instead of conservation of
energy, you have conservation of momentum. The cyclist loses all of his
speed, and has almost no effect on the speed of the car.
Jay Beattie
I would imagine that main rider impact would be against the windshield
and the leading edge of the roof -- and not the front of the car, at
least for those of us on diamond frames. It might be survivable, and
maybe not. See http://www.williamsonforensic.com/Animations.html
(scroll down). Here is a seriously greusome one.
http://www.highimpactlit.com/animations/automotive/AUT01187/ That
last one doesn't look like much fun, and I doubt a helmet would have
helped. -- Jay Beattie.
Barry
> a bat is close to a totally elastic collision.
Actually, according to "The Physics of Baseball" by Robert Adair, when a
baseball is hit by a wood bat, about 68% of the energy is lost to friction.
So, in Adair's words, "the collision is quite inelastic".
r15...@aol.com
> "bicycle_disciple" <1.crazyboy.o...@gmail.com> wrote in message
In a nutshell: Don't get hit by cars traveling near 30 mph. You'll
likely end up in the hospital or worse.
Philip Holman
"Barry" <Ba...@invalid.invalid> wrote in message
news:gke958$p6e$1...@news.motzarella.org...
My intent was to show that even in the most conservative scenario, the
energy imparted to the rider could not result in a 13 story elevation
gain.
Collisions are never totally elastic; it violates the 2nd law of
thermodynamics.
Phil H
bicycle_disciple
Phil H :
I think you proved it. It would be great if someone actually did a
simulation on something like this, but so far we have some videos that
don't sufficiently predict what can happen. I have posted a certain
simulation in the same article See http://tinyurl.com/9w34vp
BD
bicycle_disciple
wrote:
> <00bf1a1d-af67-4d40-bf6d-e1f62f855...@u14g2000yqg.googlegroups.com>,
Ecnerwal :
Given speed = 46kph or 25.12 m/s.
If we assume the cyclist was at rest when hit by the 2000 kg car
sideways,and the time of impact was say 0.5 seconds
Force of impact = m * (delta v/delta t) = 2000 * 25.12/0.5 = 100480
Newtons !
For a 70 kg man, that means you just got slapped by 146 times your own
body weight. Ouch.
Given that scenario...you know what, I'll do any damn thing to protect
my brain box..regardless of whether the helmet is going to
disintegrate like a bomb on impact.
carl...@comcast.net
Dear Phil,
I agree that a car won't launch a real and squashable cyclist 13
stories into the air, but I took your back-of-the-envelope
calculations to show that 13 stories was quite plausible for an
idealized elastic collision.
After all, you calculated ~10 stories with a 220-lb stationary bicycle
and rider hit by a car doing ~30 mph and weighing only 3300 pounds.
Not much more height is gained with a lighter 180-lb bike+rider at
81.8 kg or even the lighter bike and a heavier 5,000-lb (2272.73 kg)
SUV:
v2 = 2 (m1v1)/(m1+m2) =
2 * 2272.73 * 12.92/2472.73 = 23.754 m/s SUV vs heavy rider
2 * 1500 * 12.92/1600 = 24.225 m/s light car vs heavy rider
2 * 1500 * 12.92/1581.8 = 24.504 m/s light car vs light rider
2 * 2272.73 * 12.92/2354.1 = 24.947 m/s SUV vs light rider
h = 1/2v^2/g = 1/2*23.754^2/9.8 = 28.79 m = 94.5 feet
h = 1/2v^2/g = 1/2*24.225^2/9.8 = 29.94 m = 98.3 feet
h = 1/2v^2/g = 1/2*24.504^2/9.8 = 30.64 m = 100.6 feet
h = 1/2v^2/g = 1/2*24.947^2/9.8 = 31.75 m = 104.7 feet
All that weight-fiddling gains only about ten feet.
But what if the bicycle is moving and hits the SUV head-on? A baseball
hit from a tee doesn't go as far as a pitched ball.
This handy calculator lets us plug in a 2272.72 kg mass at 12.94 m/s
(5,000 lbs of SUV doing ~30 mph) and an 81.8 kg bike+rider doing
various speeds.
http://home.att.net/~srschmitt/script_collision1d.html
bike speed before afterward height
----------------- --------- ------
0 mph = 0.000 m/s +24.94 m/s
-5 mph = -2.235 m/s +27.02 m/s
-10 mph = -4.470 m/s +29.10 m/s
-15 mph = -6.705 m/s +31.18 m/s
-20 mph = -8.940 m/s +33.26 m/s
h = 1/2v^2/g = 1/2*27.02^2/9.8 = 37.25 m = 122.3 feet
h = 1/2v^2/g = 1/2*29.10^2/9.8 = 43.20 m = 141.9 feet
h = 1/2v^2/g = 1/2*31.18^2/9.8 = 49.60 m = 162.9 feet
h = 1/2v^2/g = 1/2*33.26^2/9.8 = 56.44 m = 185.3 feet
In other words, a light 81.8 kg rider + bike doing a leisurely 10 mph
head-on into the 5,000-lb ~30 mph SUV goes BOING! hard enough to reach
14 stories when the forces in our implausible perfectly elastic
collision are rearranged to shoot him straight up.
In real life, of course, the rider mostly squashes if he hits the car
squarely.
Cheers,
Carl Fogel
Bernhard Agthe
Ecnerwal wrote:
> In article
> <00bf1a1d-af67-4d40...@u14g2000yqg.googlegroups.com>,
> bicycle_disciple <1.crazy...@gmail.com> wrote:
>
>> I found this on a helmet advocacy website.
> ...
>> Thoughts are welcome.
Cool, then let me make out the new slogan for helmet propaganda: "Using
a helmet gets you to 13th floor faster than the elevator" ;-)
Did they use the physical law for "elastic impact"? 13th floor? That
must be a joke! 3rd floor perhaps! But only if the helmet wearer is made
from ideal rubber?!
> Helmets are primarily good for absorbing the impact of a fall from 6
> feet (2 meters) - ie, when you fall down and hit the
> ground/road/sidewalk as part of your crash, and then slide to a stop.
> Much more than that and they don't help.
So, actual bike helmets are probably suitable for pedestrians ;-)
> However, bad "science" in the name of helmet laws is a definite trend
> that also turned up in my research. I'd go with the commentator that
> suggested "total energy of the car" might be roughly equal to the
> ludicrous figure posted - the total energy of the car will not be
> imparted to the cyclist, of course.
Very likely - they used billiard balls for their calculation or
something like that?! Problem is, after watching three repetitions of
"Science TV - spectacular phenomenons" each and every kid or adult
considers himself a science professor...
You see, at least bike helmets have a very interesting effect, I often
see people wearing them and they often ride in a way I would describe as
"Helmet on, brain off"... So I see the pumpkin helmets as a quite
effective way to make bike helmets ridiculous - which they are, in a way
(at least in the way they are propagated by some self-styled "rescuers
of humankind" B-)
Ciao ;-)
Frank Krygowski
wrote:
>
>
> Given speed = 46kph or 25.12 m/s.
>
> If we assume the cyclist was at rest when hit by the 2000 kg car
> sideways,and the time of impact was say 0.5 seconds
>
> Force of impact = m * (delta v/delta t) = 2000 * 25.12/0.5 = 100480
> Newtons !
>
> For a 70 kg man, that means you just got slapped by 146 times your own
> body weight. Ouch.
>
> Given that scenario...you know what, I'll do any damn thing to protect
> my brain box..regardless of whether the helmet is going to
> disintegrate like a bomb on impact.
a) Your physics is way, way wrong.
b) If the force on the 70 kg man were 100,000+ Newtons, nothing on
earth could prevent his body from exploding into something like
hamburger.
c) If in spite of that you put your faith in a delicate styrofoam hat
- what do you put on your head when you walk across the street? Same
parameters, no?
- Frank Krygowski
Chalo
>
> Frank Krygowski wrote:
> >>
> >> Absolutely. Helmets are sold using a combination of scare tactics
> >> like those for stranger abductions of children, and "science" claims
> >> like those of the diet industry. "Lose up to 85 pounds in one week!"
>
> But if you combined helmet use with losing 85 pounds, the end result
> might be much better survivability in a collision, due to less mass
> having to decelerate.
>
> I don't understand the problem... looks like a no-brainer to me.
Especially true if the brain is left behind at the scene of the
collision.
Chalo
Chalo
>
> This handy calculator lets us plug in a 2272.72 kg mass at 12.94 m/s
> (5,000 lbs of SUV doing ~30 mph) and an 81.8 kg bike+rider doing
> various speeds.
>
> http://home.att.net/~srschmitt/script_collision1d.html
>
> bike speed before afterward height
> ----------------- --------- ------
> 0 mph = 0.000 m/s +24.94 m/s
> -5 mph = -2.235 m/s +27.02 m/s
> -10 mph = -4.470 m/s +29.10 m/s
> -15 mph = -6.705 m/s +31.18 m/s
> -20 mph = -8.940 m/s +33.26 m/s
>
> h = 1/2v^2/g = 1/2*27.02^2/9.8 = 37.25 m = 122.3 feet
> h = 1/2v^2/g = 1/2*29.10^2/9.8 = 43.20 m = 141.9 feet
> h = 1/2v^2/g = 1/2*31.18^2/9.8 = 49.60 m = 162.9 feet
> h = 1/2v^2/g = 1/2*33.26^2/9.8 = 56.44 m = 185.3 feet
>
> In other words, a light 81.8 kg rider + bike doing a leisurely 10 mph
> head-on into the 5,000-lb ~30 mph SUV goes BOING! hard enough to reach
> 14 stories when the forces in our implausible perfectly elastic
> collision are rearranged to shoot him straight up.
>
> In real life, of course, the rider mostly squashes if he hits the car
> squarely.
Ah, the Fogel Institute for Theoretical Science has come through for
us again!
But surely Fogel Laboratories for Applied Science can arrange an
experiment. There are plenty of fundamentalist Christians in nearby
Colorado Springs who have utter faith in their Almighty to protect
them from harm, so they would probably exhibit near-perfect elasticity
in a collision. They are also highly suggestible, so they could more
than likely be talked into volunteering for an experiment to advance
our understanding of what God has created. Delicate references to
Shadrach, Meshach and Abednego should motivate any hesitant
subjects.
Maybe you can get some of them to drive their 5000-pound SUVs to the
lab.
Chalo
Ecnerwal
<428a5be9-af14-4be4...@v18g2000pro.googlegroups.com>,
Frank Krygowski <frkr...@gmail.com> wrote:
> On Jan 12, 12:21 am, bicycle_disciple <1.crazyboy.o...@gmail.com>
> > Given speed = 46kph or 25.12 m/s.
> a) Your physics is way, way wrong.
I do love folks that can't even convert kph to m/s correctly.
Hint: there are 1000 meters in a kilometer. Kilo meter, get it?
There are 3600 seconds in an hour. 60 minutes, 60 seconds per minute.
The math is not that difficult. Getting it wrong by a factor of 2 is
ludicrous.
Tim McNamara
Ecnerwal <Lawren...@SOuthernVERmont.NyET> wrote:
Well, a factor of 1.96591304348 anyway. ;-)
Tim McNamara
<dfdced87-adb8-4085...@q30g2000prq.googlegroups.com>,
r15...@aol.com wrote:
> In a nutshell: Don't get hit by cars traveling near 30 mph. You'll
> likely end up in the hospital or worse.
A fine summation.
Philip Holman
<carl...@comcast.net> wrote in message
news:874af3a1-c24e-44c0...@u18g2000pro.googlegroups.com...
Dear Phil,
http://home.att.net/~srschmitt/script_collision1d.html
Carl,
you forgot that the collision has to during the vernal equinox
in dense fog.
Phil H
Michael Press
Bernhard Agthe <dark...@gmx.net> wrote:
Would be better with a tinfoil hat blocking
the government propaganda broadcasts.
--
Michael Press
alan...@sbcglobal.net
wrote:
> I found this on a helmet advocacy website.
>
> Spanish Ministry Of The Interior claimed on the site :
>
> "If a car traveling at 46.5 kph hits a cyclist, the force of impact
> would be sufficient to send the cyclist up to the thirteenth floor of
> a building."
>
> I was puzzled. While I'm all for wearing helmets for protection, I
> thought this claim might be bolder than it may seem in order to
> advance their helmet agenda. There is no data to back it whatsoever,
> so I did a small analysis using couple of real videos and some data.
> If you're interested in reading it, the link is :http://tinyurl.com/9w34vp
>
> Thoughts are welcome.
>
Guys, guys....wait, no calculations are needed here.
It's a trick question, everyone knows that there are no 13th floors in
buildings!
By the way, when I was hit by an accelerating pick-up truck and did a
little flying myself, I had the good sense to lift my head just before
impact with the street. That way I didn't need to buy a new helmet
after talking to the nice policeman and the nice ambulance-driver and
the nice doctor and the nice x-ray tech.
ABS
bicycle_disciple
Frank Krygowski :
Sorry I took the wrong mass! Ha!
Just after collision, the cyclist's velocity or change in velocity
(assuming he was at rest initially) = 25.12m/s (from momentum transfer
equation)
If that change in velocity happened in say 0.5 seconds, the
acceleration of the cyclist with his new velocity is 25.12/0.5. The
average force of the impact is Favg = m.(delta v/delta t) = 70kg mass *
(25.12 m/s / 0.5s ) = 3516.8 Newtons which is 50.24 times the
cyclist's body mass. My initial mistake came to be around 100,000
newtons which should roughly be the force with which an 600mi/hr
airplane hits a 1 pound flying duck in the air.
Frank Krygowski
What coefficient of restitution did you use?
And did you account for the possibility of a non-central impact, and
the rotational inertia of all the various body part, plus the action
of the muscles on those various parts?
I think it was Einstein who said "Things should be made as simple as
possible. But no simpler." I believe you've violated the latter part
of his advice.
- Frank Krygowski
bicycle_disciple
Frank :
I assumed COR = 1. Thats probably what you took into consideration in
your calculations as well, since it was elastic and the final velocity
of the cyclist post impact is almost twice of the approaching car.
Nevertheless, I see this as a fruitless exercise since we aren't
accounting for the real factors the DON'T send a cyclist rocketing to
the 13th floor of a building.
bicycle_disciple
Frank :
Can you account for rotational inertia of muscles and bones? And the
ruprture and breaking of those muscles and bones upon impact? I bet
this exercise isn't as easy as incorporating a "correction factor"
into the equations.
:)
Tim McNamara
<68539169-f460-4be0...@s9g2000prm.googlegroups.com>,
Frank Krygowski <frkr...@gmail.com> wrote:
> What coefficient of restitution did you use?
That's up to the court order.
Michael Press
<01c1b2b0-beb0-490f...@r37g2000prr.googlegroups.com>,
alan...@sbcglobal.net wrote:
Sorry about your trouble.
Spike TV's Manswers program showed how to be hit by a car
using a Hollywood stuntman and a compatriot at the wheel.
30 mph.
* Stand sideways to the oncoming car.
* Turn you face toward the oncoming car.
* As the car nears you, jump.
* Tuck your head.
* Turn and aim your back at the windshield.
--
Michael Press
Bernhard Agthe
Michael Press wrote:
> Bernhard Agthe <dark...@gmx.net> wrote:
>> You see, at least bike helmets have a very interesting effect, I often
>> see people wearing them and they often ride in a way I would describe as
>> "Helmet on, brain off"...
>
> Would be better with a tinfoil hat blocking
> the government propaganda broadcasts.
But don't forget the antenna so you can tell everybody that these cell
phone radiation effects you so much, you get a headache all the time :-/
Or the aliens are after you...
In a lecture a professor told us they had set up a new cell phone
antenna in some village and all the people in there started to complain
about their cows farting badly... The antenna was not even switched on
at the time. Hysteria goes a loooonnng way ;-)
Ciao..