Question

A book leans against a crate on a table. Neither is moving. Which of the following statements concerning this situation is correct?

B BYhe Learning S Spo

• A. The direction of the frictional force acting on the book is in the same direction as the frictional force acting on the crate.
• B. Although there is no friction acting on the crate, there must be friction acting on the book or else it will fall
• C. The force of the book on the crate is less than that of the crate on the book.
• D. The net force acting on the book is zero.

Answer 1

The correct option is D

The net force acting on the book is zero.

Explanation for the correct options

Option (D)

1. According to newton's third law of motion, the force exerted by the crate on the book is equal to the force exerted by the book on the crate.
2. So, the net force on the book and the crate is zero
3. Therefore we can say the force exerted on the book is zero. Since the book is fixed on the table.

Diagram

Explanation for the incorrect options

Option (A)

1. The book leans and the crate is placed on the table at rest. That's why static friction will apply here. Static friction is applied when two bodies are at rest.
2. Since the net force exerted on the book leans - crate system is zero. So, the frictional force acting on the book is opposite to the frictional force acting on the crate.

Option (B)

1. There is static friction exerted on the book leans and crate. The book leans system is placed on the table at rest. So, the book can't fall down.

Option (C)

1. The system is stable on the table, it is possible when net force is zero. So, option (C) is incorrect.

Therefore, option (D) is correct.