Q.

A body weighs 200 N on the surface of the earth. How much will it weigh half way down to the centre of the earth           [2019]
 

1 100 N  
2 150 N  
3 200 N  
4 250 N  

Ans.

(1)

Acceleration due to gravity at a depth d,

gd=g(1-dR)

For   d=R2gd=g(1-R/2R)=g2

Required weight W'=mgd=mg2=W2=2002=100 N