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: Centripetal forces and satellites

  1. Aug 22, 2011 #1
    Hi im kind of new to the forum nice to be here! here is my question.

    1. The problem statement, all variables and given/known data

    A satellite is kept in a circular orbit 300km above the surface of the earth by the force of gravity. At this altitude the acceleration due to gravity is 8.9 m/s. The radius of the earth is 6.4*10^6m

    a) calculate the period of the satellite

    b) calculate the speed of the satellite

    2. Relevant equations


    Where ac is the acceleration
    T is the period
    r is the radius


    3. The attempt at a solution


    Using the first equation listed

    T= (2(pi))(r/ac)^(1/2)

    T=5451.6 seconds

    b) Using our known T,
    V=7722 m/s

    Thanks in advance, I feel I may not have the concept down well enough and this may not be the way to do it.
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Aug 22, 2011 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    That looks right to me. Welcome to PF as a poster!!
  4. Aug 23, 2011 #3
    ** r = radius
    r = RE + h = (6.4*10^6m + 300,000m) = 6.7x10^6

    **C = Circumference


    **for circular motion there are 2 components of acceleration, radial acceleration and tangential acceleration. the radial (centripetal acceleration) is shown:


    **because gravity from the Earth is causing the satellite to undergo centripetal acceleration:

    mg = (mv2)/r

    **the masses of the satellite cancel to show the speed of the satellite:


    v = 7722 m/s

    ** the period
    T = 2(PI)r/v = 5448s

    Based on what I got, I would say you did a good job!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook