Coriolis expression - Question about sign

[Curious2013]

Homework Statement

Dear all

I have a question concerning the Coriolis acceleration expression. I learned 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!

Homework Equations

The Attempt at a Solution

 

[tiny-tim]

Welcome to PF!

Hi Curious2013! Welcome to PF!

I have a question concerning the Coriolis acceleration expression. I learned 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?

There's no Coriolis force in an inertial frame.

(same as centrifugal force)

 

[TheEtherWind]

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

 

[tiny-tim]

Here's a site that derives it as positive:

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 ​