Question

A man weighs $80$kg on the surface of earth of radius R. At what height above the surface of earth his weight will be $40$kg?

• A. $2637.6km$
• B. $3.675km$
• C. $8765km$
• D. $(\sqrt{2}+1)R$

Answer 1

The correct option is A $2637.6km$

On surface of earth $g$ is $9.81m/s^2$. The weight is given by $80kg$.

The gravitational force $\left(g\right)=\frac{G\times m_1\times m_2}{d^2}$ where $G$ is gravitational constant distance between two objects that weight $M_1$ and $M_2$. Considering weight on earth as $M_1$.

$\left(g\right)=\frac{h\times m_1}{d^2}$

Radius of earth is $6371km$ which will be halved $2637.6km$.

Therefore for a person going on earth to weight $40kg$. He has to move $2637.6km$ above earth's surface.