Chicken through the windshield

[Scorpixx]

Hi all,

I fell on those pics on the web (see attached files).

Now, there are people who tend to think this is a fake, and the others (I would be among them :) ). How to prove it ? I do not know the properties of the porsche windshield (it is a laminated windscreen of course), how much it can withstand but I guess I will be able to find that on the web by myself.

Now, let us assume the bird is about 2 kgs, the car 1300kgs. If the bird is at rest and the car is traveling at 200 kph, what would you able to say from that info ?

I assumed the collision was...inelastic. Now from what I remember the total momentum is conserved, but that didn't help much, except finding the final speed of the car.

Now my guess is I would have to compute the mass of a piece of the windshield same size as the chicken, assuming the chicken remains complete (i.e. is a strong solid) at the time of the collision...and then I determine the force (of that piece of windshield) exerted on the chicken, via the Kinetic Energy. Newton's 3rd law would say the chicken is then applying the same force to the windshield (thus, same work energy on the same distance). Any help :p ?

 

[Meir Achuz]

You have to estimate the elasticity of the chicken, because that determines the duration of the impact. Then f=m(of the chicken)*v(of the Porsche)/(duration of impact).

 

[Scorpixx]

Thank you very much Sir, I will have a look at that ! This is going to be hard determining the elasticity of the chicken (lol..) but this seems to be a very nice clue.

Edit: So I guess that from the formula you gave, we could say that as my speed increases over and over, elasticity has less and less influence.

That would be the force exerted by the chicken on the windshield correct ? Don't you have to take into account the elasticity of the windshield too ?

 

[turbo]

Looks real enough. A friend of mine hit a wild turkey with the windshield of his work van, and though the bird did not penetrate the windshield, it made a substantial shattered depression. Then again, though wild turkeys are more massive than chickens, they have a larger surface are, so they may not be as effective as a projectile, plus my friend was probably only doing 45 mph on his way to work.

 

[cesiumfrog]

You can't prove whether it is real just from a picture, but as for whether it is possible.. one thing you might want to watch is the relevant myth-busters episodes (the first of which being exemplary of the reason I no longer watch myth-busters: just because both frozen and thawed chickens passed through a cheap windshield clearly does not prove that the frozen chicken can't penetrate further, and to insist to a general audience that the physics equations definitively support such a conclusion..).

 

[wysard]

Faster than a speeding chicken

Mythbusters. Great show as long as you bear in mind the answer can at best be only as accurate as the quesiton.

So, Scorpixx given an mythological 7 milliseconds of chicken elasticity that would make your force 15, 873 kilogram meters per second. I guess you could find the strength of the windshield from the manufacturers specs and go from there.

 

[Meir Achuz]

Mythbusters. Great show as long as you bear in mind the answer can at best be only as accurate as the quesiton.

So, Scorpixx given an mythological 7 milliseconds of chicken elasticity that would make your force 15, 873 kilogram meters per second. I guess you could find the strength of the windshield from the manufacturers specs and go from there.

You no have to estimate the cross sectional area of the part of the chicken that is squashed against the windshield to get the pressure on the windshield.
It is the pressure that determines whether it cracks or not.

 

[wysard]

You no have to estimate the cross sectional area of the part of the chicken that is squashed against the windshield to get the pressure on the windshield.
It is the pressure that determines whether it cracks or not.

Oops my bad for not being clear enough. You are right of course. I calculated the total force, not the force per unit area. I made the assumption (I know, I know...lol) that from the manufacturers specs of the windshield including dimensions and using the pictures from the OP to provide an good approximation of area he could complete the calculation. Mostly because if the bird wound up all the way in the trunk it did not exceed the windshields capacity by just a little bit.

That'll learn me!

 

[Scorpixx]

Thanks a lot for your feedback. I wonder if 7 ms is close enough from reality, I will have a look inside 'impulse' problems and such. I may get some info --about the bird elasticity-- from the 'chicken gun' I guess. I will then find the specs of the windshield, see how much it can stand at that speed.