# When I change the rpm of a turntable, how long does the turntable to get to the new rpm?

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.

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.

• Seems like a fun question to approach with a vinyl recording of a constant frequency, a microphone, and a spectrogram. Mar 26, 2015 at 4:16
• 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. Mar 26, 2015 at 14:36

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.

• 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. Mar 26, 2015 at 5:21
• Yes they should.