Question

The mass of the moon is about 1.2% of the mass of the earth. Compared to the gravitational force the earth exerts on the moon, the gravitational force the moon exerts on earth
(A). Is the same
(B). Is smaller
(C). Is greater
(D). Varies with its phase

Answer 1

Hint: We can find out the answer without any calculation. According to Newton’s universal law of gravitation, the force of attraction only depends on the masses of the bodies and the distance between them. From this theory, we can find out the answer.
Formula used: $F=\dfrac{GMm}{{{r}^{2}}}$, where G is the gravitational constant, M and m are the masses of the two bodies and r is the distance between two bodies.

Complete step by step answer:
According to the law of gravitation, the objects participating in the attraction exerts the same force on other bodies. We can check this by taking the equation of gravitational force of attraction.
$F=\dfrac{GMm}{{{r}^{2}}}$, where G is the gravitational constant, M and m are the masses of the two bodies and r is the distance between two bodies.
Here you can see, masses of both bodies involved in this force of attraction. The distance between the two masses will be the same for two bodies. So, the gravitational force will be the same for two bodies that are participating in the attraction. Therefore, the correct option is A.

Additional information: We can discuss the properties of gravitational force.
The gravitational force is the weakest in nature
The gravitational force is attractive
The gravitational force is a mutual force. The bodies participating in this force of attraction, attract each body with the same forces.
The gravitational force obeys the inverse square law.
It depends only on the mass and distance between the bodies.
It is considered as the long-range force.
The gravitational force does not depend upon the medium. There is no gravitational shielding.

NOTE: Do not think that heavier mass will attract smaller masses with more force. It is a wrong concept. Both masses are involved in the force of attraction equally. The force does not depend on any other physical quantities. The gravitational force due to the earth and an object of mass 1kg placed at the surface of the earth is 9.8 N. This value is referred to as the acceleration due to gravity.