Assertion (A) : A swimmer pushes the water backward to move forward in a swimming pool.

Reason (R) : Water exerts a greater but opposite force on the swimmer, helping him to move forward.

1. both A and R are true and R is the correct explanation of A
2. both A and R are true and R is not the correct explanation of A
3. assertion is false but reason is true
4. assertion is true but reason is false

State Newton’s law of gravitation.

Write an expression for the gravitational force of attraction between two bodies of masses m₁ and m₂ separated by a distance r.

How is the gravitational force between two masses affected if the separation between them is doubled ?