Question

With the help of an experiment show that the force of friction always opposes the relative motion between the bodies​

Answer 1

Answer:

Imagine that you are pushing a box on the horizontal surface. It is clear that you are trying to produce the motion of the box relative to the surface. If there is no friction between surface and bottom surface of box in contact, you will not require any force to move the box. In other words , in the absence of friction you do not need any force to have motion of the box relative to surface. Now, it is a matter of common experience that more the roughness of the surface( or more the friction) we need more force to move the box as friction opposes the motion of the box relative to surface.