Characteristics of gravitational force :

1. Since the gravitational force act along the line joining the particles, it is a central force and so gravitational field is conservative.
2. Gravitational force is only attractive force, it is not a repulsive force and it varies as the inverse square of the distance between the two particles.
3. The value of gravitational constant \( G \) is very small, so the gravtational force becomes significant only for very large masses, e.g, in case of attraction between the planets, stars etc. This force is insignificant in case of atoms and molecules because their masses is very very small.
4. The attractive force exerted by earth on a body is proportional to the mass of the body. This mass is called gravitational mass. Again a constant force F acts upon a body, there is constant acceleration \( f \) of the body and \( F \alpha f \) and \( \frac{F}{f} \) is constant, which is called inertial mass of the body. Experiment shows that gravitational mass and inertial mass of a body are the same.