Question

At what height from the ground will be the value of $g$ be the same as

that in $10km$ deep mine below the surface of earth.

• A. 20 km
• B. 7.5 km
• C. 5 km
• D. 2.5 km

Answer 1

The correct option is A 20 km

Same changes in value of ${}^{\prime }{g}^{\prime }$ can be observe at a depth ${}^{\prime }{x}^{\prime }$

and height ${}^{\prime }2x^{\prime }$

given that the depth ${}^{\prime }{d}^{\prime }=x=10km$

$\therefore$ the same charge can be observed at a height $2x=20km$

Hence,

the correct option is $A.$