course PHY 201 Pw谟nassignment #035
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00:35:47 Query introductory problem set 9, #'s 12-17 How do we find the mass of a simple harmonic oscillator if we know the restoring force constant k and how long it takes to complete a cycle?
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RESPONSE --> by rearranging k = mg/L to be: m = Lk/g
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00:43:43 We know the basic relationship omega = sqrt(k/m), which we can solve to get m = omega^2 * k. We are given k, so if we know omega we can easily find m. We know how long it takes to complete a cycle so we can find the angular frequency omega: From the time to complete a cycle we find the frequency, which is the reciprocal of the time required. From frequency we find angular frequency omega, using the fact that 1 complete cycle corresponds to 2 pi radians.
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RESPONSE --> oops, I guess I was too busy thinking about pendulums, I automatically read ""length to complete a cycle"" as length of a pendulum. Doesn't this: omega = sqrt(k/m) become this: m = k / omega^2
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00:44:08 If we know the mass and length of a pendulum how can we find its restoring force constant (assuming displacements x much less than pendulum length)?
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RESPONSE --> k = mg / L
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00:44:20 For small displacement from equilibrium vector resolution of the forces tells us that the x component of tension in the same proportion to tension as the displacement x to the length L: x / L Since for small angles the tension is very nearly equal to the weight mg of the pendulum this gives us Tx / m g = x / L so that Tx = (m g / L) * x. Since Tx is the restoring force tending to pull the pendulum back toward equilibrium we have restoring force = k * x for k = m g / L. So the restoring force constant is m g / L.
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00:44:24 Query Add comments on any surprises or insights you experienced
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00:44:27 as a result of this assignment.
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00:44:30 .
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