Question

A man weighs $60kg$ at earth surface. At what height above the earth's weight become $30kg$, Given radius of earth is $6400km$:

• A. $2624km$
• B. $3000km$
• C. $2020km$
• D. None of these

Answer 1

Answer: (A)

$2624km$

Let acceleration due to gravity at a height $h$ above the surface of earth be $g^{\prime }$

So, $m{g}^{\prime }=m\frac{g{R}^2}{(R+h{)}^2}$
or, $30=60\times \frac{(6400{)}^2}{(6400+h{)}^2}$
So, $h=6400\sqrt{2}-6400=2624km$