Question:
The earth is acted upon by gravitation of sun, even though it does not fall into the sun. Why? (CBSE 2012)
Solution:
The earth revolves around the sun. The centripetal force is needed by the earth to revolve around the sun. This centripetal force is provided by the gravitational force between the sun and the earth. The earth keeps on moving around the sun as long as gravitational force between the earth and the sun acts on it.