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**1. Homework Statement**

Two particles of masses M1 = 81000 kg and M2 = 9400 kg are initially at rest an infinite distance apart. As a result of the gravitational force the two masses move towards each other. Calculate the speed of mass M1 and mass M2 when their separation distance is 26.5 km.

**2. Homework Equations**

**3. The Attempt at a Solution**

I think you have to use energy-conservation equations here for each mass

1/2mv1^2 - (GM1M2)/R = 1/2mv2^2 - (GM1M2)/R

so, for mass M1, v1=0 and (GM1M2)/R on the left = 0 because R = infinite. then you get

1/2m1v2^2 = (GM1M2)/R --and solve for v2, but this doesn't seem to be correct..