Question

The weight of a body at the surface of earth is $18\, N$ The weight of the body at an altitude of $3200 \,km$ above the earth's surface is (given, radius of earth $R _{ e }=6400 \,km$ ):

• A. 19.6 N
• B. 9.8 N
• C. 4.9 N
• D. 8 N

Answer 1

Answer: (D)

8 N

Answer 2

Acceleration due to gravity at height $h$
$g'=\frac{g}{[1+\frac{h}{R}]^2}$

So weight at given height

$mg'=\frac{mg}{[1+\frac{h}{R}]^2}$

=$\frac{18}{[1+\frac{1}{2}]^2}=8N$

$\text{Therefore, the correct option is (D):} 8N$