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Work on an inclined plane

  1. May 4, 2009 #1
    A block of mass M is being puled up an inclined plane at a constant speed, by an attached rope that exerts a tension T. The block is pulled a distance L. The plane makes an angle theta with the horizontal, and the coefficient of kinetic friction between the block and the incline is uk.

    a) Let E=PE + KE of the block. What is the change in the mechanical energy E of the block? What is the change in the potential energy of the block?

    b) Verify that deltaE = Wnoncons, the change in the mechanical energy of the block is equal to the work done by the non-conservative forces acting on the block.

    c) what is the Wgrav, the work done by gravity on the block? Check that Wgrav = -delta PE.

    d) Combining your results find the total work done on the block, Wtot = Wcons + Wnoncons.
    Verify that Wtot = delta KE

    any help would be much appreciated..not sure how to do this part. thanks
  2. jcsd
  3. May 4, 2009 #2


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    Homework Helper

    Welcome to PF.

    Start with a) then. The block moves at constant speed, so what is the Δ in KE? It moves L, at an angle of θ, so how much higher does it get after moving L? What does that make the Δ in PE of gravity?

    For the rest of it, what is the non-conservative force? Friction? And the work to friction is what? W = F*d = μ *m*g*cosθ ?
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