Friday, May 25, 2012

The Earth’s Force of Gravity

What is the earth’s force of gravity?

            According to science, the earth attracts everything towards its centre. It is for this reason that fruits from trees or a ball thrown up into the air, all fall to the earth surface. This invisible force of attraction between the earth and any other body is called the force of gravity.

Gravitational pull keeps the moon revolving around the earth

            The centre of gravity of the earth lies in this center. Imagine what would happen if a hole is drilled in the earth form one side to the other, passing through its centre and a ball is dropped in this hole. The ball, in fact, will stop at the centre of the earth; it will not come out form the other side. The weight of a body will be more, if it is nearer the centre of the earth.

            Similarly, the weight will be less if the body is away from it. This is why a body weighs more at the poles than at the equator, since the poles are nearer to the centre than the equator.

            Not only the earth, but all other planets have this force of gravity. As a matter of fact, every body in this Universe attracts the other body with its force of gravitations, and it is this force that keeps all the planets and stars in their places in the sky. It is this gravitational pull that keeps the moon revolving around the earth, and the earth revolving around the sun.

            Naturally, the moon also attracts the earth; tides in the seas are mainly due to the gravitational pull of the moon.

            Till the end of the 15th century, it was assumed that if two bodies were simultaneously dropped from the same height in vacuum, the heavier body would hit the ground first.

            But this assumption was found to be baseless. The famous scientist Galileo Galilei was the first to prove that irrespective of their masses, all the objects dropped simultaneously form the same point in vacuum will reach the ground at the same time. He dropped one ball weighing 100 pounds and another of just half pound at the same time from the learning tower of Pisa, and demonstrated in the presence of thousands of people that both the balls hit the ground at the same time.

            Subsequently, Newton propounded the law of gravitation. According to this law, the force of attraction between two bodies is directly proportional to the product of their masses ad inversely proportional to the square of distance between them. It follows form this that the force of attraction will be doubled if the mass of one of the two bodies is doubled.

            On the other hand, if the distance between them is doubled, the force will be reduced to one-fourth of the initial value. The velocity of a freely falling body towards the earth increases by 9.8 meters or 32 feet every second. This is called acceleration due to gravity.