Question

(a) What is force? Mention its SI and CGS units.
(b) Define atmospheric pressure.
(c) What do you mean by static and dynamic friction?

Answer 1

(a) Force is a push or pull which changes or tends to change the state of rest or state of uniform motion of an object. SI unit of force is newton (N) and CGS unit is dyne.

(b) The pressure exerted on us due to the atmosphere is called as atmospheric pressure. It is measured in the units bar and mm of Hg.

(c) The force of friction acting at the interface of two surfaces when there is no relative motion between them, is called as static friction. it is a self adjusting force.

The force of friction acting at the interface of two surfaces when there is a relative motion between them, is called as kinetic / dynamic friction. it is always less than static friction.