1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    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!

Inelastic collision problem

  1. Nov 29, 2003 #1
    A car weighing 900 kg is waiting at a stop sign. A car weighing 1200 kg hits the oter car. The cars move .76 m after the collision. The coefficient of friction between the sliding tires and the pavement is .92. I need to find the speed of the car right before the collision.
    I dont know what to use. Conservation of momentum doesnt work because I need at least one of the velocities.I can get the work done by friction fairly easily. But i can't get anywhere from there.
  2. jcsd
  3. Nov 29, 2003 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Use conservation of energy (after the collision).
  4. Nov 29, 2003 #3
    but using conservation of energy wont work because the final velocity is zero so that sets one side to zero. leaving the other side just 1/2mv^2. im trying to find the v.
  5. Nov 29, 2003 #4


    User Avatar
    Science Advisor
    Gold Member

    It's implied that this is a totally inelastic collision (the cars stick together). You can use work-energy to find the velocity of the two cars immediately after the collision:

    .5*M*(v')2 = μMgd

    where M is the total mass (1200+900), v' is the velocity immediately after the collision, μ is the coefficient of friction, and d is the distance the cars slide.

    From conservation of momentum, you have mv = Mv', where m is the mass of the first car and v is what you're trying to find.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Inelastic collision problem