At what factor between the two particles gravitational force does not depend?

1

(a)

Gravitational force does not depend upon the medium between the two particles.

Are the Kepler's laws applicable only to the solar system?

1

(a)

No, they are applicable to the artificial satellite too.

Two particles of masses m₁ and m₂ attract each other gravitationally and are set in motion under the influence of the gravitational force? Will the centre of mass move?

1

(a)

Since, gravitational force is an internal force, therefore the centre of mass would not move.

When will the Kepler's law be applicable on the planets?

1

(a)

Kepler's law will be applicable whenever inverse square law is involved.

Work done in moving a particle round a closed path under the action of gravitation force zero. Why?

1

(a)

Gravitational force is a conservative force which means that work done by it, is independent of path followed.