How to use Kepler's Third law?

Question

I'm using kepler's third law and the formula a3/p2=c

I have already asked a question regarding this formula and the person that answered it was helpful but I'm not sure how to find the cuberoot of a number. The original problem was: If a planet has a revolutionary period of 6 years, using Kepler's third law find the distance from that planet with the revolutionary period of 6 years to the Sun.

I know you plug the 6 into P

And you end up with 1au x cuberoot (36)

But how do I find the cuberoot?

And once I have the cuberoot I just multiply that by one AU and that's the distance from the planet to the sun?

Answer 1

This might sound silly, but the easiest was is to type it into your calculator on the computer.

Type in 36, hit the x^y key and then type .33333333333. Hit enter, that's the cube root.

If you don't like that answer the other ways are using a slide rule or computing a series. Trust me - use your calculator. :)

...and oh yeah. Make sure your calculator is in Scientific mode first. The x^y key is not available under the standard view.

Answer 2

If you have the calculator that comes with Windows XP, do the follwing:

Enter 36 in the display, click on the Inv box, click the x^3 button.  You'll get 3.3019 for the answer.

The x^3 button gives the cube of a number, Inv x^3 gives the cube root.