Gravitational force between point masses — common mistakes

Always remember that the distance 'r' must be measured from the centre of one object to the centre of the other. For uniform spheres, their mass can be considered at their geometric centre. A common error in exams is using surface-to-surface distance instead of centre-to-centre! When calculating net force, draw a diagram and consider the vector nature of the forces.

The extremely small value of 'G' (universal gravitational constant) means that gravitational forces are only significant and easily observable when at least one of the interacting masses is astronomically large, like planets or stars. For everyday objects, the gravitational force is usually negligible.

No, gravitational forces are exclusively attractive. They always pull masses together and never exhibit repulsive behaviour. This is a fundamental characteristic of gravity.

An inverse square law means the gravitational force decreases very rapidly as the distance between two masses increases. Specifically, if you double the distance, the force becomes four times weaker ($1/2^2 = 1/4$). If you triple the distance, it becomes nine times weaker ($1/3^2 = 1/9$).