Find the acceleration due to gravity in a mine of depth 640 m if the value at the surface is 9.800 ms^{-2} . The radius of the earth is 6400 km.
Let g be the acceleration due to gravity in mine.
Then,g′=g(1−dR)=9.8(1−640640×103)=9.8(10000−1104)=9.81049999=9.8×0.9999=9.799m/s2