Question

You can keep a 3 kg book from falling to the ground by placing it on a horizontal surface. What reaction force is resisting the force of the book on the surface?

Answer 1

This resisting force is called the normal force. It is 29.4 N on a 3 kg object.

Explanation:

Because the book is stationary, it is not accelerating either. This means the net force acting on it must total zero.

Since the only vertical forces on it are its weight (the force of gravity) and the normal force of the table pushing up on the book, these two must balance.

The weight is found by `W=mg = 3 kg xx 9.8 N/(kg) = 29.4 N`

So, the normal force must also be 29.4 N.