Coriolis force - Question about sign


by Curious2013
Tags: coriolis force, deduction, reference frame
Curious2013
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#1
Dec17-12, 12:35 AM
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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!
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A.T.
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Dec17-12, 03:48 AM
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Quote Quote by Curious2013 View Post
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 Quote by Curious2013 View Post
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.
AlephZero
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Dec17-12, 01:17 PM
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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".

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Dec17-12, 02:32 PM
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Coriolis force - Question about sign


Quote Quote by AlephZero View Post
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

(btw, this is a duplicate thread to http://www.physicsforums.com/showthread.php?t=659387)
A.T.
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Dec17-12, 05:03 PM
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Quote Quote by AlephZero View Post
The minus sign is there because humans made the arbitrary decision to use right-handed coordinate systems rather than left handed ones.
To me it seems more like it's the arbitrary decision to have ω first in the term.


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