Acceleration Due to Gravity
The uniform acceleration produced in a freely falling object due to the gravitational pull of the earth is known as acceleration due to gravity .
It is denoted by g and its unit is m / s 2 . It is a vector quantity and its direction is towards the centre of the earth .
The value of g is independent of the mass of the object which is falling freely under gravity .
The value of g changes slightly from place to place . The value of g is taken to be 9.8 m / s 2 for all practical purposes .
The value of acceleration due to gravity on the moon is about . one sixth of that On the earth and on the sun is about 27 times of that on the earth .
Among the planets , the acceleration due to gravity is minimum on the mercury .
Relation between g and a is given by
g = Gm / R 2
where M = mass of the earth = 6.0 * 10 24 kg and R = radius of the earth = 6.38 * 10 6 m .
Acceleration due to gravity at a height h above the surface of the earth is given by
gh = Gm / ( R + h ) 2 = g ( 1 – 2h / R )