Halley's Comet orbits the sun about every 75 years due to the gravitational force the sun provides. Compare the gravitational force between Halley's Comet and the sun when the Comet is at aphelion (its greatest distance from the sun) and d is about 4.5×10^12m the force at perihelion (or closest approach), where d is about 5.0×10^10m. (I really don't know where to start :( )

Answer 1

You're in a bit of a pickle if you don't know the mass of Halley's comet.
Fg = Gm1m2/r^2
You can look up the mass of the sun, but Halley's comet?
Hmm. Well I'll be. Is there anything the internet doesn't know. m1=2.2e14.
m2=1.99e30.
And away you go...