Acceleration of gravity on an unknown planet.

[flysae]

Homework Statement

A 92 kg man weighs 189 Newtons on the surface of an unknown planet. What ist he acceleration of gravity on this planet?

Basically, I thought the formula to finding the gravitational force was
G(gm)/r^2, but I'm missing the distance that the man from the planets center is. I don't know where the 189 Newtons fit in.

Homework Equations

G = (gm)/r^2

The Attempt at a Solution

G = (gm)/r^2
G = (6.67x10^-11nm^2/kg^2)(92kg)/r? What is R? I'm totally lost.

Thank you, appreciate it!

 

[Doc Al]

It's simpler than all that. If you knew the value of "g" on the planet, how would you find the weight?