# what is friction ? Types of friction

what is friction ? Types of friction:- Whenever an object actually slides or moves over the surface of another body or tends to slide, then a force opposing the relative motion acts between these two surfaces in contact. It is known as frictional force or force due to friction.

Force of friction acts tangential to the surfaces in contact in a direction opposite to the direction of relative motion.

## How many types of friction

Static Friction It is the opposing force that comes into play when one body is at rest and tends to move it over the surface of another body.

• (i) Limiting Friction It is the limiting (maximum) value of static friction when a body is just on the verge of starting motion over the surface of another body.
• (ii) Kinetic (or sliding) Friction It is the opposing force that comes into play when one body is actually sliding over the surface of another body.
• (iii) Rolling Friction It is the opposing force that comes into play when a body of symmetric shape (wheel, cylinder or disc, etc.) rolls over the surface of another body.

what is friction ? Types of friction

Angle of Friction It is defined as the angle which the resultant of the limiting friction and normal reaction makes with the normal reaction. It is denoted by a. Mathematically, tanα = μs

•Angle of Repose It may be defined as the angle of the inclined plane at which a body placed on it just begins to slide. It is denoted by 8. Mathematically, [email protected]=μ, and α = 0

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