Gravitation is defined as a force of attraction between any two bodies. Gravity is also a force of attraction exerted by the earth upon a body on or near its surface. The weight of any object at any point in the space can be defined as the resultant gravitational force, which is acting on the object caused by all the remaining objects in the space.

The motions of all the heavenly bodies have fascinated the ancient thinkers too. The invention of telescope by Galileo did facilitate the recording of the movements of astronomical bodies.

Sir Issac Newton could simplify the Kepler’s laws of planetary motion into a simple law and is termed as the law of universal gravitation. It was proved that his law is applicable not only for the heavenly bodies, but also for any two bodies in our universe.

He opined that the force of attraction between any two material objects in our universe is directly proportional to the product of their masses and also inversely proportional to the square of the distance between their centres. He could also derive several mathematical equations related to the gravitational force.

According to him, the gravitational force of attraction of any object towards the centre of the earth is equal to the weight of the object, w= mg.

The mass of any object is defined as the quantity of matter contained in it. It is constant and does not change from location to location. It can never be zero.

The earth does attract every object towards its centre. This attraction force does depend on the mass of the body and also the acceleration due to gravity at any specific location. Thus the weight of any object is the force with which it would be attracted towards the centre of the earth.

The acceleration generated b the force of attraction of the earth is termed as the acceleration due to gravity.

The falling of any object in air under the action of gravity by neglecting the air resistance can be termed as a free fall and the object is known as the freely falling body.

It was proved that in the absence of any air resistance, or in vacuum all the objects do fall at the same rate irrespective of the magnitude of their masses. But some early thinkers did assume that all the objects fall down at equal rates of velocity in the absence of air resistance!