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Q in dynamics, kinetics, Energy

  1. Nov 20, 2009 #1
    1. The problem statement, all variables and given/known data

    1 Kg block slides on a circular rod (no friction) from rest in A position by a force of 40N. What is the speed when it reached point B. (see attached pic)

    2. Relevant equations


    3. The attempt at a solution
    The energy in A is 0, the energy in B is mgh+0.5mv^2
    My problem is how to find the work of the force.


    Attached Files:

    • 1B.JPG
      File size:
      10.4 KB
  2. jcsd
  3. Nov 20, 2009 #2


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    Welcome to PF!

    Hi vemplord! Welcome to PF! :smile:

    (try using the X2 tag just above the Reply box :wink:)
    Work done = force "dot" displacement …

    so for a small angle dθ, find the displacement, "dot" it with the force, and then integrate. :smile:
  4. Nov 21, 2009 #3

    I tried that:
    The Y displacement is rsinθ an X displacement is r-rcosθ, tried to integrate from "0" to "π/2" but it doesn't come out right.

    What am i doing wrong?
  5. Nov 21, 2009 #4


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    dunno :redface:show us! :smile:
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