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## Homework Statement

What is the mass of a planet (in kg and in percent of the mass of the sun), if:

its period is 3.09 days,

the radius of the circular orbit is 6.43E9 m,

and the orbital velocity is 151 km/s.

## Homework Equations

I'm unsure what formulas to use, though these seem relevant.

F= ma

accel. centripetal = v^2/r

Total Energy = -G*(mass of planet)*(mass of sun)/2*radius

## The Attempt at a Solution

I thought I should use Force of gravity = mass of the planet times the centripetal acceleration, but the mass of the planet cancels out. I can't ID the right relationship between the period, radius and mass, so I'm not sure what to do.

Thanks for any help.

JS