Chapter 2, Problem 1EA

Give three important “laws” that characterize frictional interactions between two Solids sliding past one another.

To determine

The three important “laws” that characterize frictional interactions between two solids sliding past one another.

Answer to Problem 1EA

The three laws of friction are

1. When a body is moving the frictional force is directly proportional to the normal contact force acting on the body.

2. The friction does not depend on the area of contact between the two bodies sliding past one another but depends on the type of surface in contact.

3. The value of coefficient of static friction is slightly more than the coefficient of kinetic friction.

Explanation of Solution

The laws are summarized which will characterize the two solid bodies sliding past each other.

First law:

When a body is moving the frictional force is directly proportional to the normal contact force acting on the body.

Second law:

The friction does not depend on the area of contact between the two bodies sliding past one another but depends on the type of surface in contact.

Third law:

If two solid bodies slide over each other, then the force of friction is given by

$f_{k_{}}={\mu }_{k}N$

Where, $N$ is the normal contact force and ${\mu }_k$ is the coefficient of kinetic friction between the surface of the two bodies.

If two solid bodies do not slide over each other then the force of friction is given by

$f_s\le {\mu }_{s}N$

Where, $N$ is the normal contact force and ${\mu }_s$ is the coefficient of static friction between the surface of the two bodies.

Conclusion:

The three laws of friction are

1. When a body is moving the frictional force is directly proportional to the normal contact force acting on the body.

2. The friction does not depend on the area of contact between the two bodies sliding past one another but depends on the type of surface in contact.

3. The value of coefficient of static friction is slightly more than the coefficient of kinetic friction.