If the distance between two masses is tripled, the gravitational force between changes by a factor of

a. 1/9
b. 1/3
c. 3
d. 9

In positive numbers less than 1, the zeros between the decimal point and non zero are significant

The star betelgeuse is about 600 light-years away. if it explodes tonight, a. we'll know because debris from the explosion will rain down on us from space. b. we'll know it immediately because it will be brighter than the full moon in the sky. c. we won't know about it until 600 years from now. d. none of the above.

Suppose a comet has an orbital period of 309.1 years around the sun. what is it’s average distance from the sun?