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Coriolis and fictitious motion
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Rotating frames show apparent deflection of moving bodies.
a = −2Ω×vIn a frame rotating at Ω, a moving body seems deflected by the Coriolis acceleration −2Ω×v and pushed outward by the centrifugal term. These explain the rotation direction of cyclones and the drift of long-range shells.
In the northern hemisphere moving air is deflected to the right, so cyclones spin counterclockwise.
Coriolis effect is negligible for sinks or baths on human scales.
In more detail
In a rotating frame, objects appear to experience the Coriolis force, which deflects moving bodies, and a centrifugal effect. These fictitious forces explain the large-scale motion of winds and ocean currents.
Real-world uses
- Weather systems spin in opposite directions in the Northern and Southern Hemispheres due to the Coriolis effect.
- Artillery shells and long-range projectiles are corrected for Coriolis deflection.
- Meteorologists use the Coriolis effect to explain why hurricanes spin in opposite directions in the two hemispheres.
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Frequently asked questions
Is the Coriolis force real?
It is fictitious, arising from describing motion in a rotating frame, though its effects are real.
Does it affect a bathtub drain?
Not noticeably. The effect is too small over a bathtub for the water to show it.
Does the Coriolis effect make water spin down a plughole?
Not in a sink, because the effect is far too small over a short distance. The direction of the spin is set by the basin's shape and small initial currents.
Related topics in Kinematics
Parametric motion · Galilean transformation · Frames: inertial vs non-inertial · Chase and meeting problems · Average vs instantaneous acceleration