Q.

Assuming the earth to be a sphere of uniform mass density, the weight of a body at a depth d=R2 from the surface of the earth, if its weight on the surface of the earth is 200 N, will be (Given R = radius of earth)                              [2023]

1 400 N  
2 500 N  
3 300 N  
4 100 N  

Ans.

(4)

M=Wg=20010=20 kg

Acceleration due to gravity at a depth

        g'=g(1-dR)

d=depth from surface, d=R2

g'=g(1-R/2R)=g2=5 m/s2

Weight=m×g'=20×5=100 N