Hi everyone,(adsbygoogle = window.adsbygoogle || []).push({});

I'm really confused with a particular question:

1. The problem statement, all variables and given/known data

A space shuttle orbits the Earth at 6720 km from its centre. The gravitational field strength is 8.9N/kg. Calculate the shuttle's orbital period in minutes...

2. Relevant equations

g=4pi^2 x R /T^2

3. The attempt at a solution

The thing is, I know how to solve it using g=4pi^2 x R /T^2, but I want to know why I can't just use g=r^3/T^2 (the constant for all objects orbiting a particular mass)...if I have r and g, why can't i just use this equation???

Thanks!!

Steve

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Planetary Motion, calculation of orbital period

**Physics Forums | Science Articles, Homework Help, Discussion**