True or false? If a book is sitting still on a shelf, the shelf is exerting a constant force on the book.

Analysis of the Statement

1. Understanding Forces: In order to determine if the statement is true or false, it's important to understand the concepts of forces and equilibrium. When an object is at rest on a surface, like a book on a shelf, it is in a state of equilibrium, meaning that the forces acting on it are balanced.

2. Identifying Forces: The primary force acting on the book is gravity, which pulls it downward. The shelf exerts an upward force known as the normal force. According to Newton's third law, for every action, there is an equal and opposite reaction. Therefore, the force exerted by the shelf must be equal in magnitude and opposite in direction to the force of gravity acting on the book.

3. Constant Force: Since the book is sitting still and not accelerating, it can be concluded that the upward normal force from the shelf exactly balances the downward gravitational force. Hence, the normal force can be considered a constant force as long as the weight of the book and the conditions of the shelf remain unchanged.

Conclusion

The statement is True. The shelf is exerting a constant force on the book; specifically, this force is equal to the weight of the book, allowing it to remain at rest.