Is a simple pendulum simple harmonic motion?

  • Thread starter maccha
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  • #1
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I'm wondering this because my textbook says that for small angles it is, but we learned that for simple harmonic motion to occur there must be a linear restoring force.. eg F= -kx.. but for the simple pendulum the restoring force is F= -mgsin(theta).. wouldn't this not be linear?
 

Answers and Replies

  • #2
rock.freak667
Homework Helper
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Well you see for small angles θ, sinθ≈θ so that the restoring force is F=-mgθ.

And now you know θ=x/l (x=arc length and l=length of pendulum)

so F=-mgx/l
 
  • #3
53
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Ohh okay, makes sense. Thank you!
 

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