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Homework Help: Glancing Collision and Kinetic Energy

  1. Mar 5, 2013 #1
    A mass m1 = 6.20 kg is moving North with a velocity of v1 = 13.5 m/s when it collides perpendicularly with another mass m2 = 4.40 kg moving East with a velocity of v2 = 8.80 m/s. Mass m1 runs into mass m2 in an inelastic collision and both masses stick together and move off after the collision at an angle θ = 56.3˚.
    What will be the velocity of these two masses after the collision?
    How much kinetic energy was lost in this inelastic collision?

    My work so far:
    P initial:
    1: x - 0 y - 6.2(13.5) = 83.7
    2: x - 4.4(8.8) = 38.72 y - 0
    P final:
    1 & 2: x - 10.6(Vfcos56.3) = 5.9Vf y - 10.6(Vfsin56.3) = 8.8Vf

    I don't know what to do next.....

    Also for the kinetic energy what would I do? Thanks!
  2. jcsd
  3. Mar 6, 2013 #2


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    Science Advisor
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    Gold Member

    Momentum will be conserved in each direction, right? So equate the total x momentum before to the x momentum after, and similarly y (but either will do to determine Vf; they've given you more information than you need).
    Compute the KE before and the KE after.
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