# Law of Gravitation

Instructions: answer the questions, check them carefully, and when you are sure they are all right, press submit. The number of correct answers will be displayed.

Question 1: If the distance between two bodies is doubled, what happens to the gravitational attraction between them?

Question 2: Newton's Law of Universal Gravity assumes the mass of the Earth is concentrated at a point at the centre of the planet.
Do people feel heavier as they go down a deep mine?

Question 3: Planet Y has a mass twice that of Planet X, and Planet Y has a radius twice that of Planet X. What is the ratio of the gravitational field strength on the surface of Y to that on X?

Question 4: The escape velocity from the surface of a planet depends on:

Question 5: Gravitational potential at a point is defined as the work done

Question 6: The gravitational potential between two bodies is:

Question 7: The gravitational field strength of a mass M is:

Question 8: Two stars have the same density but star A has two times the radius of star B. What is the ratio of the gravitational field strength at the surfaces of the stars?

Question 9: What is the gravitational field strength at the surface of a planet with density ρ and radius R?

Question 10: A mass m is at the centre of a thin, hollow sphere of mass M and radius R. What gravitational force does m experience?

### Quote of the day...

The next morning began with a brief series of howl screeches, acoustically representing the dying moments of the entrance gate hinges. Considering the gate was not even closed, let alone locked, it would be safe to say whoever they were, these were not your run of the mill guests. Not that I am suggesting guests should be allowed to run the mill.