Question

At what height above earth 's surface, value of g is same as in a mine 100 km deep?

Answer 1

Solutions 

⇒ Let the variable "g" represent the height. 

g = 0 ( 1- $\frac{2h}{r}$ ) - (1) 

g = 0 ( 1- $\frac{d}{r}$  ) - (2) 

⇒ The variable "d" represents the depth or also known as how deep.  

g = 0 ( 1- $\frac{2h}{r}$ ) - (1) ≡ g = 0 ( 1- $\frac{d}{r}$ ) - (2)  

⇒   $\frac{2h}{r}$ = $\frac{d}{r}$

⇒ h = $\frac{d}{2}$ = $\frac{100}{2}$ = 50 km 

Simplify 
⇒ 50 km