Flyheel the storage energy. The transfer from mechanical energy to electric energy was equal. The situation was, i got a 1/2 hp electric motor (EM) that can turning a 5 kg flywhell (∅ 28 cm) to 1500 RPM within 10 second. (connected by gear to each other) question was: 1. at the 11 second, i turn off the EM, how much energy stored in flywheel until it stop turning. 2. at the 11 second, i turn off the EM, then the flywheel start to reduce it speed to 1300 RPM. At that moment, i'm starting turn on the EM again. How much energy from EM needs to turning and to regain the top speed of the flywheel (from 1300 to 1500 RPM).? Thanks alot for the answer.