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If the turntable was rotating at 16 rpm and I switched it to 30 rpm, is the change in speed pretty much instantaneous, or is their a period of acceleration? When I did it, the change appeared to be close to instant, but that's only from observation.

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There absolutely is a period of acceleration. Speed never changes instantly, even if it changes too quickly for you to sense with your eyes and ears, as a direct consequence of Newton's laws. Probably it accelerates over a 1/10 of a second or so, if I had to guess.

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    $\begingroup$ Seems like a fun question to approach with a vinyl recording of a constant frequency, a microphone, and a spectrogram. $\endgroup$ – zeldredge Mar 26 '15 at 4:16
  • $\begingroup$ That's a really good idea, actually. There are freely available audio spectra monitor programs available that run off a soundcard. Anyone with a turntable and a PC could attempt this experiment. $\endgroup$ – James Palmer Mar 26 '15 at 14:36
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The increase in rpm depends upon angular acceleration which is how quickly it's rpm increases (in this case) or decreases. When u increased the rpm, the change appeared instantaneous because of very small time required to increase the rpm. The less the time required, the greater tbe acceleration. So it is a period of acceleration.

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  • $\begingroup$ For example, if I go from 0 to 16, then 16 to 30, then 30 to 45, would the sum of these forces be equal to going from 0 to 45 instantly? I'm thinking they should. $\endgroup$ – L to the V Mar 26 '15 at 5:21
  • $\begingroup$ Yes they should. $\endgroup$ – Saad Mar 26 '15 at 5:31
  • $\begingroup$ But you shouldn't use the word forces. Torque would be more appropriate since the system is in angular motion. $\endgroup$ – Saad Mar 26 '15 at 5:37
  • $\begingroup$ Sorry, I haven't learn about torque yet. $\endgroup$ – L to the V Mar 26 '15 at 14:22
  • $\begingroup$ Torque you can say is the force which makes a body rotate rather than move in a straight line $\endgroup$ – Saad Mar 26 '15 at 15:29

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