Question

The gravitational field strength at the surface of a certain planet is $g$. Which of the following is the gravitational field strength at the surface of a planet with twice the radius and twice the mass?

• A. $g/2$
• B. $g$
• C. $2g$
• D. $4g$

Answer 1

Answer: (A)

$g/2$

Answer 2

For a given planet, $g = \frac{GM}{R^2}$
Gravitational field strength at the surface of another planet, $g' = \frac{GM'}{R'^2}$
Here, $M' = 2M , R' = 2R$
$\therefore \:\:\: g' = \frac{G(1M)}{(2R)^2} = \frac{g}{2}$