Question

If action force acting on a body is gravitational in nature, the reaction force:
A. may be a contact force
B. must be gravitational force
C. may be a gravitational or contact force
D. may be a force of any origin

Answer 1

Gravitational force is the force of attraction between two bodies with some mass, which is a pulling force in nature. We will use the concept of the motion's third law given by Newton to know the reaction force's nature.

Complete step by step answer:
From the concept of motion's third law given by Newton, we can state that if any force P is applied on a body, it brings a reaction force that will be equal to the magnitude of force P but opposite in direction. Also, the nature of the reaction force and applied force P will be the same.

It is given the nature of action force acting on a body is gravitational. Based on the concept of motion's third law given by Newton, we can say that the nature of reaction force will also be the same as that of action force.

Therefore, the reaction force's nature must be a gravitational force if acting force acting on a body is gravitational in nature

So, the correct answer is “Option B”.

Note:
We have to note that the reaction force's direction will be opposite to the applied force's direction.
Additional information: If we consider two particles separated by some distance, then the expression of the gravitational force between them is given by:
$F = \dfrac{{G{m_1}{m_2}}}{{{r^2}}}$
Here ${m_1}$ is the mass of one particle and ${m_2}$ the mass of another particle, G is the gravitational constant, and r is the distance between these two particles' centers.
This force F is experienced as a pulling force by both the particles.