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Frictional force : The frictional force is the force exerted by a surface as an object moves across it or makes an effort to move across it . There are two types of frictional force sliding and static fiction . Fictional results from the two surfaces being pressed together closely causing intermolecular forces between molecules of different surfaces.
ADVANTAGES OF FRICTIONS : It becomes difficult to walk on a slippery road due to low friction.
We cannot fix a nail in the wood or wall if there is no friction.It is the friction that holds the nail.
A horse cannot pull a cart unless friction furnishes him a secure foot hold.
Disadvantages of friction : Friction id very important in our daily life but it also has some disadvantages like :
1. The main disadvantage of friction is that it produces heat in various parts of machines.In this way some useful energy is wasted as heat energy.
2. Due to friction we have to exert more power in machines.
3. It opposes the motion.
4. Due to friction noise is also produced in machine.
5. Due to friction engines of automobiles consume more fuel which is a money loss.
METHODS OF REDUCING FRICTION :
There are number of methods to reduce friction in which some are discussed here.
USE OF LUBRICANTS :
The parts of machines which are moving over one another must be properly lubricated by using oils and lubricants of suitable variety.
USE OF GREASE :
Proper greasing between the sliding parts of machine reduces the friction.
USE OF BALL BEARING:
In machines where possible , sliding friction can be replaced by rolling friction by using ball bearings.
DESIGN MODIFICATION :
Friction can be reduced by changing the design of fast moving objects . The front of vehicles and airplanes made oblong to minimize friction .