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!

2D inelastic collision and K of CM

  1. Feb 20, 2009 #1
    1. The problem statement, all variables and given/known data
    Car 1 (1500kg) is heading north 80km/h, Car 2 (3500kg) is heading east 50km/h. They collide inelastically.
    a.) Speed and direction of the wreck (car 1 + car 2)?
    b.) The kinetic energy lost?
    HERE I HAVE A PROBLEM:
    c.) What is the kinetic energy of the two-particle systems center of mass before and after the collision?
    d.) Where was the lost kinetic energy hidden before the collision?

    2. The attempt at a solution
    a. is just vector sum p1+p2 where I can get the velocity by dividing it with the masses (about 12m/s), I can get the angle too (34,438... deg)
    b. wrecks K minus K of car 1 and car 2 = - 360532,40... J so about 360 kJ lost
    c. But this one I don't understand. I'd say it stays the same, because... well, that's what I calculated (CM from the v-vectors = v of CM), yet I don't really belive it...
    d. ... after all shouldn't the K be lost to deformation of bodies (+heat etc.)? Does the K of CM stay the same anyways?
     
  2. jcsd
  3. Feb 21, 2009 #2
    Ok, I found something useful on the net:
    http://courses.washington.edu/ph122mo/A08/MT3info.html" [Broken]
    # Inelastic collisions

    * momentum is still conserved
    * kinetic energy of center of mass motion cannot be lost
    * maximum energy loss for items sticking together after collision


    And that is really all I needed to know. :approve:
     
    Last edited by a moderator: May 4, 2017
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: 2D inelastic collision and K of CM
  1. 2D inelastic collision (Replies: 5)

  2. 2D inelastic collision (Replies: 8)

Loading...