1. The problem statement, all variables and given/known data A satellite is in a circular orbit around an unknown planet. The satellite has a speed of 1.70 × 104 m/s, and the radius of the orbit is 5.25 × 106 m. A second satellite also has a circular orbit around this same planet. The orbit of this second satellite has a radius of 8.60 × 106 m. What is the speed of the second satellite? 2. Relevant equations Kepler's Laws of Planetary Motion -- T2/r3 = 4pi2 / GM v = sqrt (GM / r) 3. The attempt at a solution There really isn't much conceptual work involved in this, so I might just be making an arithmetic mistake somewhere. But I've worked the problem out three times and gotten the same (wrong) answer every time... I used the v = sqrt (GM / r) -- plugged the values in for the first satellite and solved for the planet's mass which must be 2.274 x 1025 kg. Then I used that mass value for M in the same equation, switching out the radius value for the second satellite. I get that v = 1.3 x 104. But the answer is 1.3 x 10-7. Why is my answer so far off? Is the problem with the planet mass value or just in the calculations for the second satellite's speed? I think my process is right.