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 Acceleration and Satellite Question

  1. Sep 19, 2010 #1
    1. The astronaut orbiting the Earth in Figure P4.30 is preparing to dock with a Westar VI satellite. The satellite is in a circular orbit 600 km above the Earth's surface, where the free-fall acceleration is 8.21 m/s2. The radius of the Earth is 6400 km.
    a) Determine the speed of the satellite. m/s
    b) Determine the time required to complete one orbit around the Earth. min

    2. Relevant equations[/b]
    centripetal acceleration= v squared/ radius
    distance*speed= time

    3. The attempt at a solution[/b]
    To solve for the speed I used 8.21 as the centripetal acceleration and made that equal to v squared/7000 and then solved for v.

    8.21=v squared/7000
    v= 239 m/s

    I then took 14000*3.14 for the circumference of the orbit and multiplied that by 239 m/s for the total time to orbit and divided that by 60 to put the answer in minutes. I got 2919.94 minutes.

    However, both answers are wrong. Can I not use the free fall acceleration for centripetal acceleration?
  2. jcsd
  3. Sep 19, 2010 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Welcome to PF,

    Are you trying to claim that distance*speed = time? You might want to rethink that one...
  4. Sep 19, 2010 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Yes, you can, and you should, because gravity is what is providing the centripetal force that keeps the satellite moving in a circle. You might have a computation error. Can you post your calculations for part a?
  5. Sep 19, 2010 #4
    for part a I used the equation centripetal acceleration= v^2/ radius

    8.21= v^2/(6400+600)
    v= 239.73

    what is wrong with this calculation?

    Concerning finding the time. I completely forgot that t=distance/speed.
  6. Sep 19, 2010 #5
    I just realized my problem. I did not do the simple unit conversions from km to m. Everything worked out fine. Thanks for all of your help!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook