State four laws of static friction.

State four laws of static friction. 
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Answer :

1. The frictional force is always acts tangential to the plane of contact and in the opposite direction of motion. 2. When the body is in limiting equilibrium, the ratio of limiting friction to normal reaction is constant. This ratio is called as „coefficient of friction‟. 3. The coefficient of friction depends upon the nature of surfaces in contact and is not dependent on surface areas in contact. 4. The static friction is more than dynamic friction. 5. Force of friction is a self-adjusting force and it increases as the applied force increases up to limiting friction. 
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