Question

If a rock is brought from the surface of the moon
A. Its mass will change
B. Its weight will change
C. Both mass and weight will change
D. Its mass and weight will remain the same

Answer 1

Hint: To determine the possible changes in weight and mass, we study the definitions of mass and weight closely and state their properties. Also, gravity of a body is dependent on its mass.

Complete answer:
Given, a rock is brought from the surface of moon –

Mass of a body is defined as the inertia or resistance the body shows when it is subject to an acceleration. In other words, it is the count of the total number of atoms in it.
The formula of mass of an object is given as
${\text{m = }}\dfrac{{\text{D}}}{{\text{V}}}$, density D per unit volume V. And the S.I units of mass is Kilograms (Kg).
Hence from its definition it is obvious that the mass of a body does not change, as neither the density of the object nor the volume the body occupies cannot be changed, the number of atoms in it cannot be altered by just moving it from the moon’s surface to a different place.

Weight of a body is defined as the force with which it is attracted to any celestial body due to its gravity. In other terms, weight of a body on earth is the force exerted by earth on the body due to earth’s gravity.
The formula of weight of an object is given as
${\text{W = mg}}$, where m is the mass of the object and g is the gravitational acceleration acting on the object. Its S.I unit is Newton.
Hence from the definition we can say weight of a body is directly proportional to the gravitation acceleration that it is subject to and this gravitation acceleration is in relation with the object that is attracting our body.

Therefore when a rock is brought from the surface of the moon, we can say that the gravitational acceleration “g” it was experiencing on the moon need not be equal to the new gravitational acceleration it experiences on a different surface.
Hence when a rock is brought from the surface of the moon, its mass remains the same and its weight changes.

So, the correct answer is “Option B”.

Note:
 In order to answer this type of question the key is to understand that the gravitational acceleration acting on an object is in relation with the body that exerts a gravitational pull on the object, it does not have anything to do with the object experiencing the pull.
The conventional value of gravitational acceleration on earth is about: g = 9.8${\text{m}}{{\text{s}}^{ - 2}}$.