FACTORS ON WHICH THE FRICTION DEPENDS

Friction depends upon the following two factors. 

1. Normal Reaction 
2. Nature, of Surfaces 

NORMAL REACTION

Force of friction is directly proportional to the normal reaction R which acts in upward' direction against the weight of the body sliding on a surface i.e. 

NATURE OF SURFACES

Force of friction also depends upon the nature of two surfaces in contact with each other, it is constant for various pairs of surfaces in contact and this value is called co-efficient of friction. 

SELF ADJUSTING FORCE 

The force of friction' has the ability to increase its value with the increase of applied force till it reaches a maximum value..,Due to this strange nature of frictional forces we call them as the self adjusting force. It is denoted by Fs. 

LIMITING FRICTION  

Definition 

The maximum force of friction which just stops the body from moving is called limiting friction 

COEFFICIENT OF FRICTION 

Definition

 Coefficient of friction is the ratio between force of friction and perpendicular reaction. 

p is coefficient of friction. R is perpendicular reaction. F is force of friction. 

ROLLING FRICTION 

Definition :

Then a body rolls over a surface it experiences an opposing force that is called rolling friction. polling friction between two bodies is much less than the sliding friction because in rolling the contact S-Irface is much less than that in sliding. 

ADVANTAGES OF FRICTION  

• Frictional forces help us to move forward. 

• Nut and bolt can hold a body due to friction. 

• A nail stays in the wood because of friction. 

• We can not hold any thing without friction. 

• We can tie a knot because of friction. 

DISADVANTAGES OF FRICTION  

There are so many disadvantages of friction but some are as follows. 

In a car engine oil under pressure is supplied continuously to ball bearing surface. Failure of the oil supply will allow metal to metal contact and the resulting friction, often raises the temperature and due to this ball bearings and piston are sized up.