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Homework Help: Coriolis expression - Question about sign

  1. Dec 17, 2012 #1
    1. The problem statement, all variables and given/known data

    Dear all

    I have a question concerning the Coriolis acceleration expression. I learnt it as Ac = -2ω x v, where ω is the vector which indicates the rotation axis direction of Earth and v the velocity of a body that I want to check the Coriolis effect on.

    My question: where the minus sign comes from? As far as I understand, it depends on what reference frame I use (inertial or non inertial - the minus comes from the latter, like the Earth, in my conception). Am I correct?

    Thanks in advance!

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Dec 17, 2012 #2


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    Welcome to PF!

    Hi Curious2013! Welcome to PF! :smile:
    There's no Coriolis force in an inertial frame. :wink:

    (same as centrifugal force)
  4. Dec 17, 2012 #3
    The sign is solely due to the choice of coordinates. Here's a site that derives it as positive:

    http://www.nws.noaa.gov/om/wind/deriv.shtml [Broken]
    Last edited by a moderator: May 6, 2017
  5. Dec 17, 2012 #4


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    no, it derives it as negative

    Coriolis force exists only in the Earth's frame (the rotating frame),

    so in that frame (d2R/dt2)Earth is on one side of the equation, and everything else on the other side …

    the Coriolis force then does have a negative sign :wink:
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