# Coriolis force - Question about sign

by Curious2013
Tags: coriolis force, deduction, reference frame
 P: 4 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!
P: 4,008
 Quote by Curious2013 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?
You can swap ω and v, and the minus sign is gone:

-2ω x v = 2v x ω

 Quote by Curious2013 As far as I understand, it depends on what reference frame I use (inertial or non inertial
The Coriolis force exist only in non inertial frames.
 Engineering Sci Advisor HW Helper Thanks P: 7,101 The minus sign is there because humans made the arbitrary decision to use right-handed coordinate systems rather than left handed ones. The Coriolis force is just a consequece of Newton's laws of motion. The physics doesn't depend on what frame you use to describe it, or whether the frame is inertial or non-inertial. The details of the math depend on those things, but "the map is not the country", and similarly "the math is not the phyiscs".
HW Helper
Thanks
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Coriolis force - Question about sign

 Quote by AlephZero The minus sign is there because humans made the arbitrary decision to use right-handed coordinate systems rather than left handed ones.
no, it would still be there, because you'd still need v = ω x r