A chair is kept on the floor. When does friction act between them? Where does this force act? Is the magnitude of this force a constant ?

A chair is kept on the floor. When does friction act between them? Whe

1.	A chair is kept on the floor. When does friction act between them? Where does this force act? Is the magnitude of this force a constant ?
Answer» Solution :When the chair is at rest on the floor frictional force does not act. Friction comes into play when one TRIES to drag the chair over the floor and it CONTINUES to act when the chair is ACTUALLY in motion. The frictional force acts parallel to the surface of CONTACT between the chair and the floor and opposite to the direction of motion or relative motion. Magnitude of the force of friction is not a constant. As the force on the chair is gradually increased the force of friction also increases and reaches a LIMIT called the force of limiting friction . On further increase of the applied force , the frictional force decreases a little and thereafter remains constant .