# Homework Help: High school Circular Motion Help?

1. Jan 17, 2014

### Steins

1. The problem statement, all variables and given/known data
Part 1
You are traveling to Jupiter's moons:Ganymede and Callisto. You have to land on the slower moon before trying to accelerate to the faster moon. Which moon will you land on first? What must your velocity be in order to "catch up"(accelerate) to the faster moon?

Part 2
Your spacecraft weights 2.04x10^6kg and the fluid friction from the slow moom is 500,000N. The Acceleration due to gravity is 1.3m/s^2. If it takes 30 mins to accelerate to the faster moon, how much thrust does the spacecraft exert?

2. Relevant equations
G=6.67x10^-11m^3/kg^2
Ganymede: Mass=1.48x10^23kg, Semi-Major Axis=1,070,400km
Callisto: Mass=1.076x10^23kg, Semi-Major Axis=1,882,700km

3. The attempt at a solution
I used F=GMm/r^2 to find the pull between the two moons and Jupiter, and I think that the slower moon would be Callisto. But I don't think that's the right equation to use. And now I have no idea where to even start the other parts of the question.I really want to understand because I don't really get my teacher's explanation. So any help would be greatly appreciated.

2. Jan 17, 2014

### Student100

Think about this, what are the orbital speeds of the planets in the solar system? Is there some kind of relationship? Would the relationship, if it exists, be the same for juipters moons?

Now what about two planets the same distance from the sun, one with twice the mass as the other. Which planet would orbit quicker?