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Homework Help: Amount of Kinetic Energy Lost in Inelastic Collision

  1. Apr 25, 2013 #1
    1. Two carts, each of mass M, travel towards each other on a frictionless air track, one with velocity V, and the other with -3V. They collide and stick together. How much kinetic energy is lost in the collision?

    2. P = mv, KE=1/2mv2

    3. Initial KE of the system is the sum of the kinetic energies of the two masses.

    K1 = (1/2)Mv2, K2 = (1/2)m(-3v)2 = 9mv2

    sum: 10mv2

    assuming momentum is conserved, velocity of the two masses after the collision is -V.

    Then calculate final KE = 1/2(2m)(-V)2 = mv2

    subtract this from the initial and I get 9mv2 Joules are lost in the collision.

    My key says the answer is 4mv2
  2. jcsd
  3. Apr 25, 2013 #2
    K1 = (1/2)Mv2, K2 = (1/2)m(-3v)2 = 9mv2

    sum: 10mv2

    check your arithmetic.
  4. Apr 25, 2013 #3
    forgot to divide by 2... goodness. Thanks!
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