# What is friction?

Friction can be defined as a force which act at the surface of separation of two bodies in contact, and tend to oppose the motion of one over the other. Or

The force resisting the relative motion of solid surface, fluid layers or object sliding against each other

## Frictional Force

The  frictional force can be given as

F = μR

Where μ= coefficient of static friction and R is equal to the weight of the object on top or the reaction of the one on the ground and F = limiting frictional force.

### Types of friction

Static friction is the force that keeps an object at rest. This force must be overcome before that object can be moved. This kid of friction is only experienced by any object at rest.

Kinetic friction is the friction between bodies relatively in motion

Fluid friction is the friction between the layers of liquid

# Laws of solid Friction

(i). It opposes motion of machine parts

(ii). Frictional force is independent of area of the surface in contact

(ii). The frictional force is proportional to normal reaction for a give pair of surface . That is F = μR

(IV). The frictional force depend on the nature of  the surfaces in contact

(a).It make us to walk on the ground without slipping

(b). It prevent ladder from sliding

(c). It is used to convert mechanical energy to heat energy

(d). It make the brakes in our car and vehicle to work

(E). It assist the gripping of belt in machines

(f). It makes it  possible for nail to hold something on wall or for nail to hold two woods together

(1). It opposes or slows motion

(2). It causes tear and wear in parts

(3). It causes unwanted heat in our machine

(4). By opposing motion in machine it reduces its efficiency

# How to reduce Friction in our machine

(1). It  can be reduced in machine by the use of

(2).By the use of ball and roller bearings

(3). By smoothing and polishing the surface involved

(4). It can also be reduced by streamlining

Causes of friction: It is cause by, surface roughness, deformation and molecular adhesion. Adhesion is molecular force resulting from when two material are brought together