Question: Define force of gravitation.

Answer: The force of attraction which exists between any two objects in the universe is known as force of gravitation.

Question: State Newton's law of gravitation.

Answer: According to this law, "Every particle in this universe attracts every other particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them".

Question: Why is G called a universal constant?

Answer: G is known as universal constant, because its value remains the same throughout the universe.

Question: List out the physical quantities on which the gravitational force between objects depends.

Answer: The gravitational force between two objects depends on

a) the mass and

b) the distance between them

Question: What do you mean by a freely falling object?

Answer: An object which moves towards the earth due to force of gravity is described as a freely falling object.

Question: What is acceleration due to gravity?

Answer: The acceleration produced in a body due to force of gravity is known as acceleration due to gravity.

Question: Two bodies of mass 10 kg and 12 kg are falling freely. What is the acceleration produced in the bodies due to force of gravity?

Answer: The acceleration due to gravity produced in both the bodies is the same as it is independent of the mass of the body.

Acceleration produced in both the bodies 10 kg and 12 kg is 9.8 m/s2.

Question: What will happen to the force of gravitation between two objects A and B if the distance between them is reduced to half?

Answer: Let d be the distance between the two objects A and B of mass m1 and m2 respectively,

The force between A and B when distance between them is reduced to half

F1 = 4 F

i.e., the force increases.

The force of gravitation between any two objects increases by a factor 4 if the distance between the objects is reduced to half.

Question: What would you observe if there are two massive bodies A and B of equal masses which experience only force of gravitation?

Answer: The objects A and B would be moving around each other.