Question

(i) Which is more fundamental, the mass of a body or its weight? Why?
(ii) How much is the weight of an object on the moon as compared to its weight on the earth? Give a reason for your answer.
(iii) Can a body have mass but no weight? Give reasons for your answer.

Answer 1

(i) Fundamental quantities are those quantities which cannot be expressed in the form of other quantities i.e. they are independent on their own. Example: Mass, Length, Time, etc.

Since weight is the amount of downward force a body exerts, therefore it is measured in Newton(N)
The unit 'Newton' can be expressed in terms of mass, length and time, so weight cannot be considered as a fundamental quantity.

Hence, mass is more fundamental.

(ii) Weight of an object on the moon is one-sixth of its weight on the earth. Mass and the radius of the earth and the moon are different in such a way that the earth's gravitational attraction is 6 times higher than the moon's gravitational attraction.

(iii) Weight of a body is simply the gravitational pull by any planet. In space, the force of gravity becomes zero. Therefore, the weight of the body becomes zero too. As the mass is a fundamental quantity, so a body can have zero weight but not zero mass.