Question

When an electric fan is swithecd on, from where does its angular momentum come?

Answer 1

Answer:Before answering to your question, I would like to make you recall a theory of physics,Newton’s First Law of Motion. It states that a rigid body at rest stays at rest and a rigid body in motion stays in motion with the same speed and same direction, unless and until an external force is being applied to the rigid body. And this law is also referred to as Law of Inertia.

Now here according to your question, the fan here is the rigid body and the rigid body is in motion when the switch is turned on. When the fan is switched off, here rotational inertia acts upon the rotating fan