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Homework Help: Help me solve my dilema.Kinematics and dynamics of Rigid body problem.

  1. Jul 5, 2011 #1
    1. The problem statement, all variables and given/known data

    Find acceleration-x ̈ of the load. Force F=10G, friction μ=1/3, mass of he body is G.

    I tried two ways of solving this problem but not sure if any is good. I think second is good. But wondering if first is also good?

    2. Relevant equations

    Ek=1/2 G/g x ̇^2

    Fμ=G μ

    3. The attempt at a solution

    Please look at the picture.There you can see my effort in solving this problem. Thanks for any help.

  2. jcsd
  3. Jul 5, 2011 #2


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    Homework Helper

    I think you mean that the weight of the block is G, not the mass.

    The first approach is correct, but not the second. It's not true that the rate at which work is being done is equal to the increase in kinetic energy, because friction takes away some of that energy.
  4. Jul 6, 2011 #3
    Work would be dA=Fdx-Gμdx

    dA=29/3 Gdx

    from which acceleration is x=29/3 g

    For first approach I don't see how to get G μ+G/g x ̈ =F from Newton's second law?

    Thanks for your help
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