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Homework Help: Fastest speed in a Pendulm

  1. Nov 3, 2008 #1
    1. A simple pendulum is made from a 0.773-m-long string and a small ball attached to its free end. The ball is pulled to one side through a small angle and then released from rest. After the ball is released, how much time elapses before it attains its greatest speed?



    2. f = 1/2pi (g/l)^1/2



    3. I thought that maximum speed would be when the string is vertical for the first time.
    This would be when the pendulm had gone through 1/4 of a full oscillation.

    So I calculated f =.567s
    and 1/4 f = .142s,

    But this is wrong,

    Am I on the right track or way off?
     
  2. jcsd
  3. Nov 3, 2008 #2

    CompuChip

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    You thought well, but I don't think you did the calculation right. If I use the formula you provided, I get a frequency which is about 10 times larger. So you might want to redo the number crunching :smile:
     
  4. Nov 3, 2008 #3
    I have seen some problems like this that have to do with Kinetic Energy.

    Ek=1/2mv² so if you have any of the values for this, u can isolate for v like this:

    v=√2(Ek)/m

    OR.. If u can only work with potential energy you could use this equation

    v=√2g▲h

    ▲h will be the change in height.. but ur looking for time.. so.. hmm.

    You may need an equation that has "t" in it.. like P=w/t... if u could find the work done.. or something.. i dont know.. lol.. hope any of this helps.. sorry, im just starting physics! :)
     
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