Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Strange question

  1. Jun 18, 2003 #1
    So I came across a question in a quiz book the other day and I still haven't been able to answer it, so I figured I would ask some experts... Here goes...

    As a NASA senior physicist, would you agree with the calculation made by a junior physicist regarding the speed of an artificial satellite, v = 3 x 10^4 m/s, assuming that it is travelling at an altitude h = 230 km above the earth's surface where g = 9.0 m/s^2. The radius of the earth is 6370 km.
  2. jcsd
  3. Jun 18, 2003 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    I would disagree.

    For all circular motion, a = v2/r, where a is the centripetal acceleration, v is the linear velocity, and r is the radius of the circle.

    Plug the numbers in, and you'll see there's a contradiction.

    The satellite should be moving at roughly 7,000 m/s, not 30,000 m/s.

    For more info on circular motion: http://hyperphysics.phy-astr.gsu.edu/hbase/circ.html#circ

    - Warren
  4. Jun 18, 2003 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member


    If the sat is going at that speed and altitude, it won't be at that altitude for long.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook