1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Comparing gravitational force at varying distances

  1. Nov 1, 2016 #1
    1. The problem statement, all variables and given/known data
    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 x 10^12 m to the force at perihelion (or closest approach), where d is about 5.0 x 10^10 m.


    2. Relevant equations
    F=GmM/d^2
    (Not applicable because masses aren't provided?)

    3. The attempt at a solution
    I wasn't sure where to begin considering the masses were not provided, but eventually I found that the distance from the sun at the furthest distance is 90x greater than when it is at its closest point. I then assumed that it wanted to me to use Newton's Law of Universal Gravitation that as the distance is doubled the force decreases by 1/4. But I'm not sure if where to go from here.
     
  2. jcsd
  3. Nov 1, 2016 #2

    ehild

    User Avatar
    Homework Helper
    Gold Member

    .

    The problem asks the ratio of the forces, F(aphelion)/F(perihelion). Yes, use the Law of Universal Gravitation.
     
  4. Nov 2, 2016 #3
    Thank you! I've concluded that the force of the sun's pull at aphelion is only 1/8100 of whatever it is at perihelion by using the inverse-square law . It was much simpler than I originally thought, I must've been over thinking it.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted