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Homework Help: Restoring force on a pendulum

  1. Nov 6, 2012 #1
    1. The problem statement, all variables and given/known data
    What is the net force done on a driven pendulum?

    2. Relevant equations
    Fd=mk (driving force)
    Fg=mg (Gravitational force)
    Fr=????? (Do I need to include this????)

    3. The attempt at a solution
    Fnet = Fd + Fg = mk + mg

    I'm not sure if I need to include the restoring force, which was not given in the problem but I know it is there.
  2. jcsd
  3. Nov 6, 2012 #2


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    Force "done"? Unusual terminology. Does it really say that?
    Why is the driving force proportional to the mass of the pendulum? Or is this some other mass?
    Are you using g as a vector here? If not, you need to consider that not all the forces will be collinear.
    Depends what it is. There certainly is another force somewhere, or the pendulum would drop like a stone.
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