Laws of friction

There are total five basic laws of friction so now let we check it out one by one.

Experiments have shown that the force of solid friction 

• is directly proportional to the normal reaction between the two surfaces.
• opposes the motion between the surfaces.
• depends upon the materials of the two surfaces.
• is independent of the area of contact.
• is independent of the velocity of sliding.

The last of these five laws is not true in the strict sense as it has been found that the friction force decreases slightly with the increase in velocity.