# Space module problem

1. Dec 12, 2003

### cowgiljl

if the command module is 60 miles above the surface of the moon it wants me to calculate the speed of the module adn the time it takes to complete one revolutionaround the mooon?
givens

mass moon = 7.35 * 10 to the 22 power
radius moon = 1.74 * 10 to the 6 power
altitude above the surface of the moon = 60 miles

converted the 60 miles to meters which was 96540 m

Ro = Rm + h
Ro = 1.74E6 + 96540
Ro = 1.74E22

Vcm is the command module

Vcm^2 = G * Mm/ro
Vcm^2 = 6.673E-11 * 7.35E22/1.74E22
Vcm = 1.679 meters/sec

and not sure if this is right and don't know what to use to figure out the time it took to make 1 revolution

thanks

2. Dec 12, 2003

### cowgiljl

on the time part of it should i use kelpters law?

3. Dec 13, 2003

### enigma

Staff Emeritus
Period can be found by using this formula:

$$P = 2\pi \sqrt{\frac{a^3}{\mu}}}$$

Where a is the semimajor axis (the radius for circular orbits, like your problem)
and mu is the gravitational parameter, or G*M