# Kepler's Law and Non-terrestrial Orbits (Not Earth)

## Homework Statement

A satellite orbits a planet at a distance of 6.80 multiplied by 10^8 m. Assume that this distance is between the centers of the planet and the satellite and that the mass of the planet is 3.08 multiplied by 10^24 kg. Find the period for the moon's motion around the earth. Express the answers in earth days

## Homework Equations

Kepler's 3rd Law
Period² = (4(pi)radius³)/(Gravitational Constant * Mass of Massive Body)

## The Attempt at a Solution

I have the answer in days of this planet, however, I don't know how to get the answer in Earth days.

7779136.049 = Period.

I'm incredibly sure this is a correct value, I've done multiple calculations and always got within 0.1% of this value

I saw this question in the archive, but I don't believe anyone realized the answer was in Earth days or they just did not show their work (which is what I was hoping to see).

Found my problem, needed to divide by days represented in seconds (Period / (60 * 60 * 24));

Answer was 90 days. (decimal dropped out of laziness, forgive me significant digits.)

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HallsofIvy
Homework Helper
HOW did you get it "in days of this planet" when nothing is said about the planet's rotation?

D H
Staff Emeritus

## Homework Equations

Kepler's 3rd Law
Period² = (4(pi)radius³)/(Gravitational Constant * Mass of Massive Body)

## The Attempt at a Solution

I have the answer in days of this planet, however, I don't know how to get the answer in Earth days.

7779136.049 = Period.
How did you go from Kepler's third law to 7779136.049? What are the units for this number?

In other words, show your work. It's a bit difficult to find where your mistake is if you don't show us how you arrived at your result.

## Homework Statement

A satellite orbits a planet at a distance of 6.80 multiplied by 10^8 m. Assume that this distance is between the centers of the planet and the satellite and that the mass of the planet is 3.08 multiplied by 10^24 kg. Find the period for the moon's motion around the earth. Express the answers in earth days

## Homework Equations

Kepler's 3rd Law
Period² = (4(pi)radius³)/(Gravitational Constant * Mass of Massive Body)

## The Attempt at a Solution

I have the answer in days of this planet, however, I don't know how to get the answer in Earth days.

7779136.049 = Period.
How did you get the radius of planet X if the question on,y mentions the satellite's orbital distance?

gneill
Mentor
How did you get the radius of planet X if the question on,y mentions the satellite's orbital distance?