1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Quick help needed for some homework

  1. Oct 5, 2009 #1
    Hi all, struggling with a question.

    A vehicle of mass 600kg, moving at a speed of 30m/s, collides with a stationary vehicle of mass 900kg. The two vehicles lock together on impact. Calculate

    a) The speed of the vehicles immediately after impact

    b) the force of the impact, if the duration of the collision was 0.15s,

    c) the acceleration of each vehicle during the collision.

    I've done part a, but struggling with b). Any help much appriciated, no numeric answers though please.

    Thanks all
  2. jcsd
  3. Oct 5, 2009 #2


    User Avatar
    Homework Helper

    Force= rate of change of momentum
  4. Oct 5, 2009 #3
    I know that, but is it the rate of change of momentum for the whole system, as the moving car slows down, whereas the stationary car speeds up after the collision. So how would I find the change in momentum?
  5. Oct 6, 2009 #4
    Can anyone help, I really need this homework done?
  6. Oct 6, 2009 #5


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Change = Final value - Initial value

    You are right, one car slows down and the other speeds up and the momentum of either car changes. What is the sum of the two momentum changes, though?
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook