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# Harmonic approximation watch

1. So, I've a problem that says:

A particle of unit mass moves on teh positive x-axis under the force
F = 36(x^-3) - 9(x^-2).

Show that in the harmonic approximation the period of oscillation is T = 16pi/3.

Now, I'm not really sure what is meant by harmonic approximation. Any idea/suggestions/hints?
2. For SHM the (restoring) force must be directly proportional to x. (F=-kx) The harmonic approximation would be the range of values of x for which this is (approximately) true.
3. (Original post by Stonebridge)
For SHM the (restoring) force must be directly proportional to x. (F=-kx) The harmonic approximation would be the range of values of x for which this is (approximately) true.
So, I would set the given equation for force equal to -kx?
4. You need to find the zero of F (ie equilibrium), then taylor expand to 1st order about it, which will give the constant k.

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