Question

(a) Define mass of a body. What is the SI unit of mass?
(b) Define weight of a body. What is the SI unit of weight?
(c) What is the relation between mass and weight of a body?

Answer 1

(a) Mass of a body is defined as the quantity of matter(Solid, liquid or gas) contained in the given volume of the body. Mass is a scalar quantity. SI unit of mass is kilogram.

(b) The force felt by a body towards the center of the earth due to earth's gravitational attraction is known as the weight of the body. The SI unit of weight is Newton.

(c) We know that Force = (Mass)$\times$(Acceleration).

The weight of a body is actually the gravitational force applied by the earth.

Hence, we can write, Weight = (Mass)$\times$(Acceleration due to gravity) = m$\times$g = mg

So, the weight of a body is given by the product of its mass and acceleration due to gravity.