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Homework Help: Force question

  1. Nov 1, 2006 #1
    I am completely stumped on this one...

    Imagine that in a movie chase scene, the director wants a 1000-kg car traveling at 15 m/s to run head-on into a brick wall without knocking over the wall. If the wall brings the car to rest in about 0.2s, roughly what force will the car exert on the wall during the collision?
  2. jcsd
  3. Nov 1, 2006 #2
    We know that [tex]F = ma[/tex] and we are after [tex]F[/tex] and know the mass [tex]m[/tex] (1000kg). So we need to find the acceleration [tex]a[/tex] (which in this case is actually slowing the car down) - and we can find this from our formulas. We know the initial velocity and the final velocity - and the time it takes to change from these different speeds.

    From this the answer should present itself. If not, please explain where you are stuck.
  4. Nov 1, 2006 #3
    Adding to what HalfMan said, remember that, assuming constant acceleration, [itex]a=v/\Delta t[/itex].
  5. Nov 1, 2006 #4
    ok so I can just use F = m (vf-vi/tf-ti)?

    With that equation, I got 75,000N.
  6. Nov 1, 2006 #5
    That looks good.
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