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Homework Help: Work energy and momentum

  1. Feb 23, 2010 #1
    Your cat "Ms." (mass 7.00 kg) is trying to make it to the top of a frictionless ramp 2.00 m long and inclined upward at 30.0 degrees above the horizontal. Since the poor cat can't get any traction on the ramp, you push her up the entire length of the ramp by exerting a constant 100 N force parallel to the ramp.

    If Ms. takes a running start so that she is moving at 2.40 m/s at the bottom of the ramp, what is her speed when she reaches the top of the incline? Use the work-energy theorem.

    So i'm not sure on how to even start this problem. I know that the work-energy theorem tells you that the work done by the hand pushing the cat must equal the change in mechanical energy of the cat. And I'm pretty sure that both KE and gravitational PE will change.
    please help.
  2. jcsd
  3. Feb 23, 2010 #2


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    Yes, you are correct. However, calculating the total change in gravitational PE, from beginning to end, is something you should find pretty easy (you almost already know what that is). So if you properly add up all known energies, either already in the system, or given to the system (gravitational PE, KE, W, or otherwise), you should be able to figure out the final kinetic energy.
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