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Simple Harmonic Motion Pendulum problem

  1. Oct 19, 2014 #1
    1. The problem statement, all variables and given/known data
    A simple pendulum of length =30.0cm is released from rest from an angle of θ=10.0∘ to the vertical.
    Assuming that the pendulum undergoes simple harmonic motion, find its maximum speed.

    Source: https://isaacphysics.org/questions/accuracy_shm_pendulum_num
    2. Relevant equations
    a) v=wA
    b) T=2pi*root(L/g) --possibly?

    3. The attempt at a solution
    so w=root(g/L) by subbing equation a) into b).
    g=9.81 and L=0.3.

    so v=root(9.81/0.3)*(0.3-0.3cos10)
    =0.02606... ms^(-1)

    But that isn't the correct answer?
  2. jcsd
  3. Oct 19, 2014 #2


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    A is the amplitude of oscillation, not the length of the pendulum.
  4. Oct 19, 2014 #3
    Is A=0.3-0.3cos10 ?
  5. Oct 20, 2014 #4
  6. Oct 20, 2014 #5


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    How did you come up with this number? How far away from the equilibrium is the pendulum when it is at an angle of 10 degrees?
  7. Nov 9, 2014 #6
    Its maximum velocity will be at the lowest point. The total length is 0.3m. Its current vertical height distance from the top is 0.3cos10. So the difference is 0.3-0.3cos10 which is the maximum amplitude..?
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