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Car-wall collision problem

  1. Mar 4, 2013 #1
    car-wall collision problem (urgent)

    1. The problem statement, all variables and given/known data
    What net force is acted upon the car by the wall during the collision. Explain your answer along with what assumptions you made.


    2. Relevant equations



    3. The attempt at a solution
    http://www.youtube.com/watch?feature=player_embedded&v=ywJ3WGpf0hw

    This video is the example of the question. So im not sure what the question mean by the net force acted upon the car.
     
    Last edited: Mar 4, 2013
  2. jcsd
  3. Mar 5, 2013 #2
    I'm not that great at this stuff, but what have you attempted so far?
    You should start off by thinking of what equation to use and drawing a Free Body Diagram
    Keep in mind Newton's Third law
     
  4. Mar 5, 2013 #3
    There is no equations, its an explanation problem. The only thing i can come up with is the force the car exerts on the wall will be same exact but opposite force the wall exerts back to the car. So the momentum of the car and wall added together should be zero because from the video you can see the car stops right after crashing, and did not bounce back.
     
  5. Mar 5, 2013 #4
    Right, maybe the car slams into the wall and comes to an immediate stop after traveling at a constant velocity and ending with a velocity of 0?
    I think if it was equal and opposite the car would have bounced back--it didnt occur in this case.

    "Either the wall is so massive that it accelerates/moves an imperceptible amount or it doesn't move at all, in which case the force of the collision actually acts on the entire planet - which is, obviously, so massive that the effects are negligible."

    I havn't really gone over collision problems in my lectures yet. So im not entirely sure :smile:
     
  6. Mar 5, 2013 #5

    ehild

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    Gold Member

    You see that the car comes to stop, and deformed during that time. The wall exerts a force that is opposite to the velocity of the car. If you know the time period Δt of the collision you can find the average force by using change of momentum = impulse : -mv=FΔt.

    ehild
     
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