# Talk:Gravity

## Exercise

The Apollo Command Module

On July 20, Neil Armstrong and Buzz Aldrin became the first humans to land on the Moon. While Armstrong and Aldrin did important research on the surface of the moon, the third astronaut, Michael Collins orbited in the command module above. Determine the height (read: distance from the surface of the moon) at which Collins orbited in the command module by exploiting the following data. The moon has been approximated to weigh 7,3477×1022kg, and the radius to 1 737,10 km. The mass of the command module was 30,320 kg. Collins stayed in lunar orbit for 59 h 30 m. The command module did exactly 30 laps around the moon in this time. Assume that the orbit was circular and that the command module was very light compared to the moon.