Friction

Friction

Friction is a force which acts in opposite direction to the direction of motion at the surface of separation of two bodies and opposes the motion between the two bodies.

When force Ff                 is applied to the load with wight  =mg and normal reaction as shown above,the frictional force  Fr . R=mg

opposes the motion.

when the value of the load is increases, R increases , the value of the limiting frictional force Fr

increases. Therefore, the limiting frictional force is directly proportional to normal reaction.

Fr

R=mg

where μ=coefficient of limiting friction or static friction. 

Characteristic of frictional force

1. Friction depends on normal reaction R.  Fr
2. frictional force opposes motion Ff -Fr=ma
3. it depends on the nature of the surface
4. it is independent of area in contact but depend on the mass
5. it is independent of relative velocity between the surface.

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