Acceleration due to gravity

Acceleration due to gravity || BringMeKnowledge || 

Magnitude of gravity

When a body is released from a height, it freely falls towards the surface of the earth. While falling, its velocity goes on increasing so that it posses a uniform acceleration. Thus, when a body falls freely, it has a acceleration equal to the acceleration due to gravity of the earth. Hence, acceleration due to gravity is defined as the acceleration produced in a freely falling body due to the force of the gravity of the earth. It is denoted by "g" and its SI unit is "m\sec^2" Its average value is "9.8 m\s^2".  

The acceleration due to gravity  near the surface of the earth is about 9.8 m\s^2. It means that velocity of a body rises by 9.8 m\s^2 each second if the air resistance is neglected. Thus, acceleration of the freely falling body is 9.8 m\s^2. Similarly, if the body is thrown upward, its velocity decreases ( retardation) by 9.8 m\s^2 every second.

Falling bodies and acceleration due to gravity.

According to the legend, Galileo Galilee, simultaneously released iron balls  of different masses from the top of the Leaning Tower of Pisa. these balls reached the ground simultaneously which proved that all the bodies of different masses fall with the same acceleration.                                    In 1590 AD, Galileo did an experiment to demonstrate it. Before Galileo, it was thought that the speed with which a body falls to the ground depends on its mass. Higher the mass, more speedily it falls to the ground. Similarly, lower the mass, the more slowly it falls to the ground. This assertion was Aristotle's thought which proved to be wrong.

If a stone and a feather are allowed to fall from a height, the former falls to the ground much more quickly than the latter. This may give a wrong conclusion supporting Aristotle's idea. The actual fact is that the air resistance on the large surface area of the light feather is very large compared with the force of gravity on it. Air resistance as well as gravity (acceleration due to gravity )  determines the rate at which the body falls toward the earth. In other simple words, the acceleration of  freely falling bodies does not depend on mass; it is found to be equal for all bodies. 

It means two bodies, one heavier and another lighter, fall freely at the same rate if there is no air resistance or air resistance is neglected. That is they have the same acceleration equal to 'g' at every point during the motion, irrespective of their mass. If air resistance is excluded, the feather falls with the same acceleration as the stone. This was first demonstrated by Robert Boyle shortly after Galileo's death.