Question

Force on earth revolving around sun is example of
A. Normal Force
B. Reaction Force
C. Centrifugal Force
D. Centripetal Force

Answer 1

Hint: Centripetal force is the force that keeps objects revolving around the center. It is the force that constantly changes the direction of centripetal acceleration, which acts in the tangential direction to the circular path. It is felt as a pull towards the center.

Complete answer:
Let us understand the forces, given in the options before answering.
Normal Force is the force applied by the surface, so that the object does not fall through the surface, by the surface, in the direction perpendicular to the surface. Thus, it is a contact force. But, there is no contact between the Sun and the Earth.
Reaction Force can be described from Newton’s 3rd law which states that - “for every action there’s an equal and opposite reaction”. So, due to the gravitational pull by the Sun and the Earth, there’s an equal reaction force on the Sun from Earth. Nonetheless, it does not contribute to the revolution of Earth.
Centrifugal Force is the outward force applied by the rotating object, in a non – inertial frame of reference. It is an imaginary force.

Centripetal Force is the force that keeps the body revolving in a circular motion towards the center. It is the force that keeps the Earth revolving around the Sun.

So option D is the correct option.

Note:
The non-inertial frame of reference, we mentioned above is the frame of reference of Earth, where Earth appears to be stationary while the Sun appears to move.
One might assume that there’s also action of centrifugal force. It is not so, because we can observe the centrifugal force only from the Earth’s frame of reference while it is in motion and it's completely imaginary.