Question

The acceleration due to gravity at a depth "d" reduce to 25% from the value at the surface. Calculate the value of "d" if the radious of the earth is 6400km.

Answer 1

g1=g(1-d/R)

Here, g1=25 % of g i.e (25/100)g

So, (25/100)g=g(1-d/R)

1/4 = 1-d/R

d/R= 1-1/4

d=(3/4)R

Now,putting value of R as 6400

d= (3/4)6400

d= 4800 km