friction type of friction

 

Friction

Friction is a force between two surfaces that are sliding, or trying to slide, across each other. For example, when you try to push a book

           Along the floor, friction makes this difficult. Friction always works in the direction opposite to the direction in which the object is moving, or trying to move.                                                                                               TYPES OF FRICTIONS

Static Friction

 

Static friction acts on objects when they are resting on a surface. For example, if you are hiking in the woods, there is static friction between your shoes and the trail each time you put down your foot (see figure below).. Without this static friction, your feet would slip out from under you, making it difficult to walk. In fact, that’s exactly what happens if you try to walk on ice. That’s because ice is very slippery and offers very little friction.      

LIMITING FRICTION

The maximum friction that can be generated between two static surfaces in contact with each other. Once a force applied to the two surfaces exceeds the limiting friction, motion will occur. For two dry surfaces, the limiting friction is a product of the normal reaction force and the coefficient of limiting friction.

DYNAMIC FRICTION

Kinetic friction, also known as dynamic friction or sliding friction, occurs when two objects are moving relative to each other and rub together (like a sled on the ground).

ROLLING FRICTION

Rolling friction is the frictional force that occurs when one object rolls on another, like a car's wheels on the ground. This is classified under static friction because the patch of the tire in  contact with the ground, at any point while the tire spins, is stationary relative to the ground.

SOME BASIC DEFINATIONS

 

 

Angle of friction

For the maximum angle of static friction between granular materials

For certain applications, it is more useful to define static friction in terms of the maximum angle before which one of the items will begin sliding. This is called the angle of friction or friction angle.

 

Angle of repose

The angle of repose, or critical angle of repose, of a granular material is the steepest angle of descent or dip relative to the horizontal plane to which a material can be piled without slumping. At this angle, the material on the slope face is on the verge of sliding. The angle of repose can range from 0° to 90°

Coefficient of friction

A coefficient of friction is a value that shows the relationship between two objects and the normal reaction between the objects that are involved. The coefficient of friction depends on the objects that are causing friction. The value is usually between 0 and 1 but can be greater than 1. A value of 0 means there is no friction at all between the objects; such is possible with Superfluidity.

NORMAL REACTION
The component of contact force normal to the surfaces in contact is called normal reaction. It is the force acting perpendicular to two surfaces in contact with each other. It is a measure of the force holding the two surfaces together.

 FRICTION IN EQUBILLIUM

When the frictional force is at its maximum, the body in question will either be moving or will be on the verge of moving. The maximum frictional force (when a body is sliding or is in limiting equilibrium) is equal to the coefficient of friction × the normal reaction force.

Everyday Examples of Sliding Friction

·        Rubbing both hands together to create heat.

·        A sled sliding across snow or ice.

·        Skis sliding against snow.

·        A person sliding down a slide is an example of sliding friction.

·        A coaster sliding against a table.

·        A washing machine pushed along a floor.

·        An iron being pushed across material.