Question

A book is sitting on a desk. what best describes the normal force acting on the book

Answer 1

the upward force the desk pushes on the book.

from the free body diagram of the book, it is clear that on the book, there are two forces acting.

1) normal force F by the desk in Upward direction.

2) force of gravity by earth in downward direction.

The Upward normal force by the desk on the book balances the force of gravity by earth in downward direction. that is why the book remains stationary on the desk.

Answer 2

The forces acting upon the book are shown below. The force of gravity pulling downward and the force of the table pushing upwards on the book are of equal magnitude and opposite directions. These two forces balance each other.