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: Period of a satellite orbiting Earth

  1. Aug 27, 2011 #1
    1. The problem statement, all variables and given/known data

    A satellite is orbiting Earth 4200 km from Earth's surface. Considering the trajectory to be a circle, calculate the period of the orbiting satellite.

    2. Relevant equations


    3. The attempt at a solution

    Well, the textbook gives the mass of the Earth to be M=5,98*1024 kg and the radius of Earth RE=6,38*106 m

    So the radius of the orbit is R=RE+4200 km=10,58*106 m

    Now off to find the gravitational acceleration for the satellite at the given distance (which is also the centripetal acceleration in this case)



    a=3,56 m/s2

    a=v2/R => v=sqrt(a*R)
    v=6,14*103 m/s


    And now for the period

    v=c/T => T=c/v
    T=10820 s

    The textbook says it ought to be 8300 s. Where did I go wrong? Have double checked the numbers, so dont think its a calculation error.

    Thanks in advance,
  2. jcsd
  3. Aug 27, 2011 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    I get the same answer you do. The book's answer is wrong.
  4. Aug 27, 2011 #3
    This post may be redundant, as I'm not sure exactly what you did on the second half, but...

    If you use the Newtonian variation of Kepler's third law, the number pops out straight away!
  5. Aug 28, 2011 #4
    Thanks guys.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Similar Threads for Period satellite orbiting
Reducing the mortgage period