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!

Homework Help: Quick question about Oribtal Velocities

  1. Jul 25, 2012 #1
    1. The problem statement, all variables and given/known data

    I was reading in a book a little section about orbital velocities.

    It states:

    For elliptical orbits, consider a body moving from point A to point B. The total work done by the force on the body is given by

    W = KE (for B) - KE (for A)

    2. Relevant equations

    3. The attempt at a solution

    Since W=Fd, does the KE simply represent the kinetic energy?

    Thank you.
    Last edited: Jul 25, 2012
  2. jcsd
  3. Jul 25, 2012 #2


    User Avatar
    Science Advisor
    Homework Helper

    Hi ZedCar! :smile:

    Yes, the work energy theorem says that the change in energy equals the work done.

    Since the only energy that changes for an orbiting body is the kinetic energy, and the only force is gravity, that means the change in kinetic energy equals the work done by gravity.

    (We ignore the gravitational potential energy, since it is defined as minus the work done by a conservative force, such as gravity … and we cannot count it twice! :wink:)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook