Question

At what height above the surface of earth the value of acceleration due to gravity would be half of its value on the surface of earth? (Radius of the earth is 6400 km)

• A. 2561 km
• B. 2650 km
• C. 3200 km
• D. 9800 km

Answer 1

Answer: (B)

2650 km

Answer 2

The ratio $\frac{g'}{g}=\frac{R^2}{(R+h)^2}=\frac{1}{2}$ or $R+h=\sqrt{2R}$ or $h=(\sqrt2-1)R$ or $h=(0.414)\times6400.$ $\Rightarrow$ h=2650 km