Question

A planet has a gravitational acceleration on its surface of 0.5 times Earth's gravitational acceleration on its surface. The planet's radius is two times Earth's radius. What is the mass of the planet, in terms of Earth masses, ME?

Hint: Write equations for the gravitational acceleration on the surface of the planet and on Earth's surface in terms of their respective masses and radii. Then write the relationships between Earth's and the planet's gravitational accelerations, and between the Earth's and the planet's radii. Substitute your expressions into your gravitational acceleration equation for the planet. Compare your result with the gravitational acceleration equation for Earth. You can solve both for G, for example, or gEarth, and set them equal to each other, or you can divide both equations. Your answer should be a number multiplied by ME, all other constants should drop out or cancel.

Answer 1