You may have noticed that sometimes, the brushless motors in your RC planes or multirotors do not spin freely after you've been flying but at other times they spin very freely indeed.
Why is this?
Well it's probably caused by the fact that the FETs in your ESC retain a charge that works to keep them turned on so that they effectively act like brakes on your motors -- until that charge leaks away.
Try the experiments in this video yourself and see what I mean.