Orbital mechanics: Io, white dwarf, Milky Way, and Earth satellite

[smw1016]

1.
Calculate the orbital period for Jupiter's moon Io, which orbits from the center of the planet.

2.
A white dwarf is a collapsed star with roughly the mass of the Sun compressed into the size of the Earth. What would be (a) the orbital speed and (b) the orbital period for a spaceship in orbit just above the surface of a white dwarf?

3
Given that our Sun orbits the galaxy with a period of 200 at a distance of from the galactic center, estimate the mass of the galaxy. Assume (incorrectly) that the galaxy is essentially spherical and that most of its mass lies interior to the Sun's orbit.

and
To how many Sun-mass stars is your estimate equivalent?

4
At what altitude will a satellite complete a circular orbit of the Earth in 1.8h ?

thank you thank you!

 

[mgb_phys]

Welcome to PF - when you submitted the question did you see some instructions about showing you work and what you had attempted?
Telling you the answers is no different from us just saying that the answer sheets are in the top left drawer of the teachers desk.

 

[smw1016]

yea there were 15 questions and i solved them all but this ones... i don't know where to start.. please help me thank you

 

[mgb_phys]

1, lookup orbit or orbital period. For a small body orbiting a much larger one there is an equation only containing the mass of the larger body and the radius. You should be able to find the mass of Jupiter and the radius of Io's orbit on wikipedia.

 

[smw1016]

Welcome to PF - when you submitted the question did you see some instructions about showing you work and what you had attempted?
Telling you the answers is no different from us just saying that the answer sheets are in the top left drawer of the teachers desk.

yea there were 15 questions and i solved them all but this ones... i don't know where to start.. please help me thank you