Question

What is the cause of friction? what is the reason of using the frictionless pully ?
Define angle of friction?

Answer 1

Answer:

What is the Cause of Friction?

Friction is caused by the interlocking of irregularities in the surface of two objects which are in contact with each other.

What is the reason of using the frictionless pully?

The frictionless bit means that no force is required to overcome friction from the pulley rotating around it's axis and and also means that the pulley turning or not has no influence over the problem.

Define angle of friction?

The angle made by the resultant ( of frictional force and the normal reaction ) with the normal reaction is called angle of friction

Answer 2

Explanation:

Friction is the force which opposes the motion of an object/body which is in contact.

It is the opposition that we observe as the force of friction or just friction, between them. For example - A book is lying on the table. Because it has friction between two surface a table and a book.