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Homework Help: Collision between two cars

  1. Nov 24, 2009 #1
    1. The problem statement, all variables and given/known data

    The driver of a 3850 lb Pontiac traveling East at 32 miles/hr has a collision with a 3100 lb Toyota traveling East at 24 miles/hr. The coefficient of restitution is .27. Find:
    i) The final speed of the Pontiac after the collision
    ii) The final speed of the Toyota after the collision

    3850lb = 1744kg
    3100lb = 1404kg
    32 miles/hr = 46.93 ft/s
    24 miles/hr = 35.2 ft/s
    Cr = .27

    2. Relevant equations

    I'm attempting to solve i) and ii) using the equation:


    3. The attempt at a solution

    I need to do the work in ft/s & kg

    Appx - 40.26 ft/s for m1'
    Appx - 43.45 ft/s for m2'

    Does it look right for this type of problem?

    iii) The kinetic energy lost in the collision

    KE = (1/2)(m)(v2 )

    KE (m1) = (1/2)(1744kg)(14.3m/s)2
    KE (m1') = (1/2)(1744kg)(12.27m/s)2
    KE (m2) = (1/2)(1404kg)(10.73m/s)2
    KE (m2') = (1/2)(1404kg)(13.24m/s)2

    KE (m1) appx = 178315
    KE (m1') appx = 131644
    KE (m2) appx = 80823
    KE (m2') appx = 123058

    (178315+80823) - (131644+123058)

    4436 Joules lost :)

    iv) Suppose the cars locked together during the collision. Find the final speed of the 2 cars after collision for this case



    = 41.7 ft/s
    Last edited: Nov 24, 2009
  2. jcsd
  3. Nov 24, 2009 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper

    Re: Collisions

    Looks good. I haven't checked your arithmetic in detail, but your method looks sound.
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