Satellite orbital time without any numbers

[rasen58]

A satellite moves in a low circular orbit about a spherical earth that has no atmosphere (it barely skims the surface of the earth). Approximately how many minutes will it take the satellite to make one revolution around the earth?

 

I think you would use Kepler's third law here, but there are no numbers and the answer choices are 80,82,84, and 86 minutes.

How do you do this?

[swansont]

It's circular motion, meaning the gravitational force is a centripetal force.

 

You're told it's earth rather than some random planet, so you can probably use known earth values in the problem.

[rasen58]

Oh okay, that worked for me, just didn't realize I should've used the earth constants. Thanks.