# Friction in Physics

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Friction in Physics.

Types of Friction Force

Static Friction

• The opposite force that comes into play when one body tends to move over the surface of another body but actually motion has yet not started is called static friction.
• The magnitude of static friction is not constant; hence it is a self adjusting force.

Limiting Friction

• As we increase applied force, a stage comes when the body is just at the verge of moving over the other, the static friction at this stage is maximum. This maximum value of static friction is called limiting friction.

Rolling Friction

• When two bodies actually roll on each other (as in case of ball bearing), the rolling friction comes into play. Sliding Friction

• When two bodies actually slide over each other, sliding friction comes into play.
• Rolling friction is always less then the sliding friction i.e.,

Rolling Friction < Sliding Friction

• When a person pushes the ground in backward direction, force of friction is in the forward direction.
• In cycling, rear wheel is pushed in backward direction and hence force of friction is in forward direction. Front wheel moves by itself, hence force is in forward direction and therefore, the force of friction is in backward direction.
• When pedaling is stopped, both the wheels move by themselves. So, force of friction is in backward direction.
• Rolling friction is always less than the sliding friction and hence it is easier to move a heavy object on rollers rather than to slide it. This property can be attributed to the fact that in case of rolling friction, the area of contact between the two surfaces is far less. #### JEE Main

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