Question

A book is on the table. If the weight of the book is 25 newtons, what is the magnitude and direction of the normal force?

Answer 1

I'm not sure about the magnitude, but the direction of the normal force is upward. 

Answer 2

Magnitude : 25 N

Direction: upward

Explanation:

The weight of the book is 25 N and is directed downward: this is the force exerted by the book on the table.

As stated in Newton's third law, for every object A that exerts a force on an object B, object B exerts an equal and opposite force on object A.

In this case, object A is the book and object B is the table. Based on Newton's third law, we can say that the table exerts an equal and opposite force on the book: therefore, the magnitude of the normal force is equal to the weight of the book (25 N), while the direction is opposite (so, upward).