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Homework Help: Work and energy

  1. Aug 10, 2008 #1
    A block of mass m is pushed off with an initial speed u so that it moves up a rough plane inclined at an angle @ to the horizontal. the friction between the block and the plane is R. Deduce an expression for the velocity v of the block after it has moved a distance d along the inclined plane. Explain any additional symbols in your expression.

    which is correct:

    (1) 1/2mu^2 - mgd sin @ - Rd = 1/2mv^2
    v = [ (mu^2 - 2mgd sin @ - 2Rd) / m]^1/2

    (2) 1/2mu^2 - mgd sin @ - Rd = mgd sin @ + 1/2mv^2
    v = [ (mu^2 - 4mgd sin @ - 2Rd) / m]^1/2

    AND WHY?

    thank you.
  2. jcsd
  3. Aug 11, 2008 #2
    Are you asking us to do you homework for you?
  4. Aug 12, 2008 #3

    well, i did it. Just get different answer from the answer given. Asking why is it like that because i dont understand, is this called asking you all to do my homework for me? well, personally, i dont think so. but if you think so, then it's fine with me. I'll apologize.
  5. Aug 12, 2008 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Why don't you explain how you arrived at each expression?
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