You are on some moon with no atmosphere (in a space suit obviously). The moon has a radius of 2×105 km. You drop a rock from a height of 10 meters, and it takes 4.5 seconds to reach the ground. a) What is the mass of the moon?

b) If you were in a circular orbit around this moon at 14000 km how long would it take to complete one orbit?

c) I'm pretty comfortable falling 2 meters (provided I land on my feet). What height above the ground would be "equivalent" to falling 2 meters on this planet? Disregarding that I'm probably wearing a big heavy space suit, on this airless moon, lets say I mass 70kg, and my legs compress 0.5m when decelerating from a fall.

Hints:

Consider energy.

In order to stop myself, my legs can produce some force over the distance that they compress. They can do some fixed amount of work.

The work my legs do is more than just my initial potential energy.