Chapter 5, Problem 1CQ

Define normal force. What is its relationship to friction when friction behaves simply?

To determine

What is normal force, and its relationship with the friction?

Answer to Problem 1CQ

Force in perpendicular direction of the surface is known as "normal force". Friction force is directly proportional to the normal force and it is expressed mathematically as

  $f=\mu N$

Explanation of Solution

Normal Force:

Normal force is the force that acts in perpendicular direction to the surface that an object contact.

Friction force:

Friction is a force that opposes the relative motion between systems in contact. Friction force is always present between present systems. Friction force always acts in the opposite direction of the motion.

The magnitude of the friction force is directly proportional to the normal force, mathematically it is expressed as

  $\begin{array}{c}f\propto N\\ f=\mu N\end{array}$

Here,

  $f$ is the friction force

  $\mu$ is the coefficient of friction

  $N$ is the normal force

Conclusion:

Friction force tends to oppose the relative motion of the systems.