Question

A book rests on a table. A small horizontal force of 2N is applied on it but it does not move. What is the reason for this? What is the magnitude of this force?​

Answer 1

When a object is surface contact with another object.

There are interlocking between surface irregularity.

These interlocking have tendency to prevent relative motion at point of contact of object.

For prevent this relative motion, these interlock produce force opposite to motion of object at point of contact to a certain value.

This opposition force is called friction force.

Now come to question:

A book rests on a table.

A small horizontal force of 2 N is applied on it but it does not move.

On apply force it does not move, it means there are some resistance force.

This resistance force is called friction force.

There are no motion, so friction force value is equal to apply force.

Means magnitude of friction is 2 N.