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GingerBread27
Nov21-04, 03:49 PM
Assume an asteroid's moon is 1.6 km wide, and 148 km from the center of the asteroid, which is 55 km long. The moon's orbit is circular with a period of 21 h.

Whatis the mass of the asteroid?

Ok This has to do with Kepler's Laws and I don't really understand Kepler's Law. I tried using the Law Of Periods so I did (75600 s)^2=((4pi^2)/(GM))*(148 km)^3. I get the wrong answer so I don't know what I did wrong. Any ideas?
Doc Al
Nov21-04, 04:00 PM
It's a circular orbit. Use what you know about centripetal acceleration and gravity.
Doc Al
Nov21-04, 04:09 PM
Ok This has to do with Kepler's Laws and I don't really understand Kepler's Law. I tried using the Law Of Periods so I did (75600 s)^2=((4pi^2)/(GM))*(148 km)^3. I get the wrong answer so I don't know what I did wrong. Any ideas?
Of course there is nothing wrong with using Kepler's law! (Which is equivalent to what I suggested.) Be careful with units---convert km to m.