1. Jul 21, 2016

### Clara Chung

1. The problem statement, all variables and given/known data
The question is attached
2. Relevant equations
Kepler's laws and gravitational equations

3. The attempt at a solution
the question gave me a and T, I related it with Kepler's third law a^3/T^2, then I don't know what to do next. The answer of part a is 1.27 x10^17 /r^2 , part b = 1.9 x 10^27, How can I find GMm as the question only provided a and T?

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2. Jul 21, 2016

### BvU

What did you get out of Keplers third law ?

3. Jul 21, 2016

### Clara Chung

If I assume a=r, I can get GM?

4. Jul 21, 2016

### BvU

I think you can ignore the excentricity, yes.

5. Jul 21, 2016

### Clara Chung

How can I get m after that?

6. Jul 21, 2016

### BvU

Kepler's third law says a^3/T^2 is 'constant', namely ...
(They only ask for M of Jupiter and that's >> m of moons)

7. Jul 21, 2016

### Clara Chung

Thanks I got part A and B

Last edited: Jul 21, 2016