suppose that the acceleration of an object is zero. Does this mean that there is no force acting on it?

not necessarily. It could mean that the forces acting on the object are balances and that the net force of the object is 0.

Explanation:

An example would be if you get a book on the table. It doesn't move; however, the force of gravity pulls downwards onto it while the normal force of the table will try to push up on it. These forces will be equal but opposite and are balanced.

a

explanation:

no diagram was provided, but i'm guessing it's the one i've attached to my answer.

here, a mechanical force turns the rod.   this generates an electric current in the coil, which powers the bulb.

b.a device that inputs heat into a cool object