Explain Friction . Mention the methods used to decrease friction .

Explanation

Friction : It is a contact force parallel to the surface in contact friction will always oppose relative motion between the bodies .
Friction is a necessary evil . Friction is a must at some places and it must be reduced at some places .
Methods to reduce friction :
(1) Polishing : Friction causes due to surface irregularties . So by polishing friction can be reduced to some extent .
(2) Lubricants : By using lubricants friction can be reduced . Lubricants will spread as an ultra thin layer between the surfaces in contact and in friction decreases .
(3) A thin cushion of air maintained between solid surfaces reduces friction .
Ex: Air pressure in tyres .
(4) Ball bearings : Ball bearings are used to reduce friction between machine parts.
Ball bearings will convert sliding motion into rolling motion . As a result friction is reduced .