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Homework Help: Having homework trouble

  1. Apr 6, 2007 #1
    here is my problem:

    The surfaces are frictionless. The tracks are 60degrees from horizontal. A 350 kg mass is released from rest on a track at a height 3.2 m above a horizontal surface at the foot of the slope. It collides elastically with a 468 kg mass initially at rest on the horizontal surface. The mass 468 kg slides up a similar track. The acceleration of gravity is 9.8m/s^2.

    Part 1) What is the speed of the block 468 kg immediately after the collision? Answer in units of m/s.

    Part 2) To what maximum height h2 above the horizontal surface will the mass 468 kg slide? Answer in units of m.
  2. jcsd
  3. Apr 6, 2007 #2


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    What have you attempted thus far?
  4. Apr 6, 2007 #3
    Nothing, i'm completely stumped, I don't even know where to begin. this class has just driven me crazy. I'm having a baby in a few weeks and just cannot figure this stuff out it's completly warn me out.
  5. Apr 6, 2007 #4


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    Staff: Mentor

    What textbook are you using for this class. What does it say about what happens in elastic collisions? Is any particular quantity conserved?

    Congratulations on the upcoming baby, BTW!
  6. Apr 7, 2007 #5


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    You just draw force arrows (composants) for the initial configuration (all forces). In the elastic collision no kinetic energy is transformed to heat.
    Potential energy ( initial) Becomes kinetic energy when you release the 350kg, and in the collision the two bodies "share" the energy so that linear momentum is conserved. Then the kinetic energy of the 468kg is transformed into potential energy (when it slides up the slope).

    This is the procedure for ALL basic mechanics problems. Find all forces, draw composants, find the acceleration, energy (if elestic and no friction, that means no kinetic energy is transformed into heat) and momentum conservations.
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