Friction Force: A Reflection on Forces and Motion

What is the magnitude of the friction force of the wall on the book?

The magnitude of the friction force of the wall on the 3.0-kg book is 66 N. But how is this calculated?

Calculation of Friction Force:

To find the magnitude of the friction force of the wall on the 3.0-kg book, we need to determine the normal force and then use the coefficient of static friction to calculate the friction force.

Understanding the Calculation:

When a 3.0-kg book is held at rest against a wall by a 120 N push force, the static friction force between the book and the wall comes into play. The coefficient of static friction is 0.55, which means for the book to remain at rest, the static friction force needs to counteract the push force and maintain equilibrium.

To calculate the friction force, we first need to calculate the weight of the book, which is equal to the mass times acceleration due to gravity. In this case, the weight of the book is calculated as W = 3 kg * 10 m/s² = 30 N.

Since the book is at rest, the normal force acting on it is equal to the push force against the wall, which is 120 N.

Using the formula for static friction force (Fs = μs * N), where μs is the coefficient of static friction and N is the normal force, we can calculate the static friction force as follows: Fs = 0.55 * 120 N = 66 N.

Therefore, the magnitude of the friction force of the wall on the 3.0-kg book is 66 N, which balances the push force and keeps the book at rest against the wall.