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Homework Help: Conservation of kinetic energy/linear momentum problem

  1. Nov 3, 2013 #1
    1. The problem statement, all variables and given/known data
    An 8-kg sphere A is moving to the left with a velocity of 15 m/s when it strikes the 45° inclined surface of a 10-kg block B which is moving to the right a 5 m/s. The ball strikes the block 1 meter above the ground. The block is supported by rollers and impact is perfectly elastic. Determine the speeds of A and B after the impact.

    2. Relevant equations
    1/2mb(vb)^2 + 1/2ma(va)^2 = 1/2mb(vb)^2 + 1/2ma(va)^2 (initial kin. energy = final kin. energy)
    mbvb + mava = mbvb + mava (initial linear mom. = final linear mom.)

    3. The attempt at a solution
    I know to use those 2 equations to solve for the 2 unknowns Vb final and Va final, but the only thing that's messing me up is what to do with the 45° incline on the block, and I think that the ball striking the block 1 foot about the ground is irrelevant, but I'm not positive. Any help is much appreciated.
  2. jcsd
  3. Nov 4, 2013 #2
    Try and resolve the 'v' of the inclined block into its horizontal component. And then put the derived 'v' into the equation.
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