1. Not finding help here? Sign up for a free 30min 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!

Gravtational Potential Energy

  1. Nov 21, 2012 #1
    1. The problem statement, all variables and given/known data

    9. What is the total energy needed to place a 2.0 x 10^3-kg satellite into circular Earth
    orbit at an altitude of 5.0 x10^2 km?

    10. How much additional energy would have to be supplied to the satellite in question 9
    once it was in orbit, to allow it to escape from Earth’s gravitational field?

    3. The attempt at a solution

    9. I was trying to use the equation

    Wpl = (- GMem/Ro) - (-GMem/Re)
    Wpl = ( - (6.67 x10^-11 Nm^2/s^2)(5.98 x10^24)(2 x 10^3 kg)/(5 x10^5m)+(6.38 x10^6m)) - (- (6.67 x10^-11 Nm^2/s^2)(5.98 x10^24)(2 x 10^3 kg)/6.38 x10^6m))

    Wpl = - 11.59494186 x 10^10 + 12.50363636 x10^10
    Wpl = 0.908717 x 10^10 J

    IS THIS CORRECT?

    and what can i do for Question 10 ?
     
  2. jcsd
  3. Nov 21, 2012 #2

    gneill

    User Avatar

    Staff: Mentor

    Placing a satellite in orbit requires not only that you move it up to the required distance in the Earth's gravitational field, but also that you impart the required speed for it to orbit (otherwise it would just fall straight back down). So there's gravitational PE involved as well as KE.

    One point that's not covered in the problem statement is whether or not you can take advantage of the initial speed of satellite due to it being launched from the surface of a rotating Earth; If you launch from the equator in the appropriate direction, you begin with an initial speed due to the Earth's daily rotation.
     
  4. Nov 25, 2012 #3
    ok so .... i am guessing you use the work of placement to find the speed?
     
  5. Nov 25, 2012 #4

    haruspex

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    No, the work of placement is what you're trying to determine. How fast does a satellite in circular orbit at radius r have to be travelling to stay there?
     
  6. Nov 25, 2012 #5
    yes thats for number 9 .. you are completely right about that;... but for the number 10 .. second question you are finding the binding energy correct?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Gravtational Potential Energy
  1. Potential energy (Replies: 1)

  2. Potential Energy (Replies: 5)

Loading...