Question

Height at which the value of $g$ becomes $1/4th$ to that on earth is

• A. R
• B. 4R
• C. 2R
• D. $\frac {3}{2}R$

Answer 1

Answer: (A)

R

Answer 2

$g' = \frac{r\, R^2}{(R + h)^2}$ i.e. $\frac{1}{4} = \frac{R^2}{R+h^2}$ i.e. $\frac{1}{2} = \frac{R}{R+h}$ i.e. (R + h) = 2 R i.e. h = R