Question

An astronaut on a strange planet finds that acceleration due to gravity is twice as that on the surface of Earth. Which of the following could explain this?

• A. Both the mass and radius of the planet are twice as that of Earth.
• B. Mass of the planet is half as that of Earth, but radius is same as that of Earth.
• C. Both the mass and radius of the planet are half as those of Earth.
• D. Radius of the planet is half as that of Earth, but the mass is the same as that of Earth.

Answer 1

Answer: (C)

Both the mass and radius of the planet are half as those of Earth.

The expression for acceleration due to gravity on the surface of a planet is given by $g=\frac{GM}{R^2}.$

if g on the other planet is double then this will be satisfied by the only condition in option C.

in option A, g on other planet is half that of the earth.

in option B, g on other planet is half that of the earth.

in option D, g on other planet is four times that of the earth.

so the best possible answer is option C.