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.
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.