State the laws of friction and explain each of them 

• Friction force oppose relative motion between surfaces in contact.

Explanation; surfaces have projections with small area. When in contact, the surfaces rest on each other’s projection.  Because of the actual area of contact being small, high pressures exist at the points of contact and a force which opposes motion is developed.

• Friction force is independent of area of contact provided normal reaction is constant.

Explanation; When the object is turned over so that different surfaces are presented, the actual area of contact is approximately the same

• The friction force is directly proportional to the normal reaction.

Explanation; when the load increases, the pressure at points of contact increases the actual area of contact producing stronger bonds and increases the degree of interlocks. A greater force is therefore required for motion to take place.

Dr. Bbosa Science