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Homework Help: Pendulum homework problem help

  1. Dec 6, 2009 #1
    original pendulum of mass 11 kg with a period of 1.6 sec, displaced an angle of 12 degrees from the vertical. What would its acceleration be in the vertical (y) direction as it reachs the lowest point on its swing?

    wouldn't it just be -9.8? (since its just the force of gravity acting on it)
  2. jcsd
  3. Dec 6, 2009 #2
    Re: Pendulum

    It is a pendulum, which means it is attached by a rod or string. In either event, what does that do to the force of gravity at the low point?
  4. Dec 6, 2009 #3
    Re: Pendulum

    umm...not sure...
  5. Dec 6, 2009 #4
    Re: Pendulum

    Well if you look at the free body diagram the tension in the rod cancels out the force of gravity.
  6. Dec 6, 2009 #5
    Re: Pendulum

    ok so its just zero
  7. Dec 6, 2009 #6
    Re: Pendulum

  8. Dec 6, 2009 #7
    Re: Pendulum

    you need more information to solve the problem. you need to know the tension in the rod or string that's supporting the pendulum. Then you will be able to solve the eqn
    ΣF=ma=mg-T Cos θ
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