Question

Explain why the value of g is zero at the centre of the earth

Answer 1

Acceleration due to the earth's gravity is zero at the centre of the Earth because at that point the mass of the earth is equally distributed in all directions, so pulling equally in all directions for a net zero pull. 

 As the distance from the centre decreases, the acceleration due to gravity also decreases.
 At the centre the distance is zero, hence gravity is zero.

Answer 2

At the centre of the earth all the forces due to the earths gravitational field would be balanced. 
Hence g would be 0.


Hope this helps