1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Inelastic Collisions in One Dimension

  1. Jul 16, 2005 #1
    Here's my problem:

    Car A (mass 970 kg) is stopped at a traffic light when it is rear-ended by car B (mass 1600 kg). Both cars then slide with locked wheels until the frictional force from the slick road (with a low mk of 0.23) stops them, at distances dA = 5.8 m and dB = 3.6 m. What are the speeds of (a) car A and (b) car B at the start of the sliding, just after the collision? (c) Assuming that linear momentum is conserved during the collision, find the speed of car B just before the collision.

    The name of the section that this problem corresponds to is the title of this thread. I know about the conservation of momentum (ma(va1) + mb(vb1) = ma(va2) + mb(vb2), where a and b are the cars and 1 and 2 is initial and final) and the equation for the center-of-mass velocity ((pa1 + pa2)/(ma + mb)), but I don't know what to do with the friction. Should I find the frictional forces and integrate them to get the final momentums?
  2. jcsd
  3. Jul 16, 2005 #2
    Nevermind, I can't believe I didn't think of this earlier. I just realized that, after the collision, the kinetic energy transfers completely to thermal energy, so I was able to find va2 and vb2 from K = 1/2v^2. Then, applying the equation for conservation of momentum, I was able to find vb1.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook