Friction - Class 11 PDF Download

A Friction is a kind of force created by rubbing and can slow things down and then ultimately stop them.

When two objects or bodies are in contact with each other then a force comes into play. What makes the tires of the car wear away? What makes the Machine parts which come in contact with each other wear away subsequently? What makes the match sticks burn when they are scratched on an unequal surface? What makes us slip on a wet floor?

The answer to all these questions is an imaginary force called Friction which comes into execution when two bodies or objects come in contact. Rough surfaces create more friction than smooth one.

Definition of Friction

Friction can be defined in many different ways, some of them are:

Friction is a force that always exists between two bodies that are in contact with each other.

or

The opposing force of nature or the force which opposes motion of objects or bodies. or

Friction is the force which basically resists the relative motion of objects, solid surfaces, and even fluid layers sliding over each other. 

or

Friction can be defined as a force which is against an object when it touches another object. 

or

When an object moves over the surface of another object, its motion is always opposed by a retarding force that resists motion. This retarding force is called friction and it always acts in the direction opposite to the motion of the object.

Types of friction

i)Static friction

ii)Dynamic friction

a)Sliding friction

b)Rolling friction Friction : advantageous or disadvantageous with example. Friction is usually called a necessary evil. It means that it is essential in games and sports. Without friction we cannot give a better performance for example athletes use spikes and football players use studs to have appropriate friction, without friction they are unable to run fast. Even gymnasts use lime powder on their palms to perform on horizontal bar, Uneven bar and roman rings. On the other hand friction is disadvantageous in some games. In cycling there should not be more friction between road and the tyres of the cycle. If there is more friction there will be more wastage of energy of the rider and leads to damage of equipments.