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Homework Help: Show the relative difference in clock time between plane/ground is

  1. Mar 14, 2014 #1
    1. The problem statement, all variables and given/known data
    http://puu.sh/7vC46.png [Broken]
    http://puu.sh/7vBG5.png [Broken]
    Note: In this image the ohm symbol represents the angular frequency of the earth's rotation

    2. Relevant equations
    Gamma = 1/SQRT(1-v^2/c^2)
    V (relative to centre of earth) = angular frequency(R+h) +/- v
    v= plane velocity dependent on direction
    R= radius of earth
    h= height plane is flying

    3. The attempt at a solution
    The first part about showing it isn't dependent was easy and I just did some basic algebra. However, the second part is problematic.I can't seem to get to the equation it's asking for using the 2 tricks suggested. I think possibly because I'm using the wrong velocities when putting in Gamma(earth) and Gamma(plane)

    The velocities I used were
    V(plane) = Angular frequency*(R+h)+/-v
    V(Earth) = Angular frequency*(R+h)
    I put those into the gamma formular and went from there. I think I might be using the wrong velocities and have mucked up the inertial frames or something.
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Mar 14, 2014 #2


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    Gold Member

    For what it's worth, I was able to derive the equation using
    V(Earth) = Angular frequency*R

    I figured since that clock is on the Earth, there's no reason to include "h" for that particular clock (The "h" is still present in the planes' velocities though).

    But, and this is a big "but," I also had to assume that [itex] \frac{\Omega^2 h^2}{c^2} [/itex] and [itex] \frac{\Omega h v}{c^2} [/itex] were negligible compared to other, similar terms and can be neglected (contrasted with terms like [itex] \frac{R \Omega^2 h}{c^2} [/itex] and [itex] \frac{R \Omega v}{c^2} [/itex] which are obviously much larger). That particular approximation wasn't spelled out in the problem statement, so I'm not sure if my method is "correct" either. :redface:
  4. Mar 14, 2014 #3
    Omg... Wow thank you so much. I can't believe I overlooked that haha :P
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