Question

A rock has a mass of 25kg on earth. What will be its mass on the moon given that the value of g on the moon is one-sixth the value of g on the Earth.
(A) 25 kg
(B) 2.5 kg
(C) 250 kg
(D) 40 kg

Answer 1

There are two quantities which are to be kept in mind they are mass and the weight. Mass is the amount of matter contained in the body. Units of mass are kg while the unit of weight in newtons.

Complete step by step answer:
Moon is a satellite of the earth. The universal law of gravitation holds everywhere. It is due to the gravitational force of the earth which holds all the bodies. If a body is allowed to fall freely from a certain height than it falls under the influence of gravity and the acceleration of the body is g whose value is 9.8 $m/{{s}^{2}}$
So, weight on the earth, W=mg, where m is the mass of the body
Weight of body on the earth, W=$\dfrac{mg}{6}$
But the mass remains intact in any place in the universe. So, the mass does not change and it remains the same no matter whether the body is on earth or is at the moon or is at the Saturn. Hence the mass remains the same and is 25kg.
Hence, the correct option is (A)

Note: The value of g given in the question is misleading. It has no use. Mass is the amount of matter contained in the body. Had the question talked about weight then its value would have changed and the infarct value of g changes from pole to equator.