Coriolis effect

Discussion in 'Physics & Math' started by flameofanor5, Nov 7, 2009.

  1. flameofanor5 Not a cosmic killjoy Registered Senior Member

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    What exactly is the Coriolis effect? Try to explain it in words for the uneducated, (as in me.)
     
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  3. christa Frankly, I don't give a dam! Valued Senior Member

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  5. christa Frankly, I don't give a dam! Valued Senior Member

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    it seems to me its how a person views things from different point of views.
     
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  7. flameofanor5 Not a cosmic killjoy Registered Senior Member

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    Thanks =P
     
  8. CheskiChips Banned Banned

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    No. Wind coming off the North Pole moving south has no horizontal or rotational motion (but the earth does). The Earth rotates beneath the air and so the result is winds that effectively move opposite to the Earths rotation.
     
  9. James R Just this guy, you know? Staff Member

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    The Coriolis effect is an apparent force felt by objects moving North or South, due to the Earth's rotation.

    Since the Earth rotates as a rigid body, the equator rotates a lot faster than mid-latitudes. Suppose you're in a plane flying south from the tropic of Cancer towards the equator. As you fly south, the Earth's rotation is getting faster underneath you, so to you it seems as if your plane is being pushed westward by some mysterious force - the Coriolis force.

    The Coriolis force is the reason that weather systems rotate. Air masses moving towards or away from the equator are "pushed" around in circles as they try to move from high pressure regions to low.
     
  10. D H Some other guy Valued Senior Member

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    The coriolis effect affects any object moving along the surface of the Earth, not just those moving northward or southward.

    The Coriolis effect when discussed in the context of the Earth is about the horizontal deflection of an object that is moving horizontally, with velocity measured from the perspective of the rotating Earth. There is a vertical deflection called the Eotvos effect due to eastward motion. Vertical motion in turn causes a eastward/westward deflection. I'll ignore the effects on/by vertical motion. I'll also ignore that the Earth is not truly spherical (it is better modeled as an oblate spheroid). Some key concepts regarding the (horizontal) Coriolis acceleration due to horizontal motion:
    • The magnitude of the Coriolis acceleration is proportional to speed. Whether the object in question is moving north, south, east, or west doesn't matter in terms of the magnitude of the effect.
    • The magnitude of the Coriolis acceleration is proportional to the sine of latitude. The effect is greatest at the poles, zero at the equator, and changes sign at the equator.
    • The direction of the Coriolis acceleration is always normal to the velocity. The effect makes moving objects curve to the right in the Northern hemisphere but to the left in the Southern hemisphere.
    • Because the effect is always normal to velocity, it does not change the magnitude of the velocity vector. It instead turns the velocity vector.
    • The effect is solely the result of looking at things from the perspective of a rotating reference frame. An inertial observer will see zero Coriolis acceleration.
     
  11. temur man of no words Registered Senior Member

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    Imagine two (wide) moving walkways next (and parallel) to each other, moving with different speeds. Imagine you are walking on one of them across the direction of the movement of the platform. When you cross the line between the two walkways as you step on the other platform, because of the speed difference you will feel a force. This is the Coriolis force. Now you imagine a moving walkway consisting of many narrow bands, or micro-walkways if you will, each moving with different speeds, but the speed varying slowly. This is essentially the situation with Earth since near the equator the surface moves faster than the surface near the poles.
     
  12. James R Just this guy, you know? Staff Member

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    You're right, of course. I over-simplified things. The force is proportional to \(\omega \times v\), where \(\omega\) is the Earth's angular velocity vector and \(v\) is the velocity vector of the moving object.
     
  13. noodler Banned Banned

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    .

    Note that, if you were above the north pole the direction of rotation of the polar vortex in both hemispheres would look the same (assuming you can see through the earth); the left or right handed assignment is because we align the northern hemisphere "upwards"...
     
  14. stereologist Escapee from Dr Moreau Registered Senior Member

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    There are claims that water drains either CW or CCW due to the Coriolis effect. That is not true. The Coriolis effect is too small at the scale of tubs of water to have any effect. This has not stopped enterprising folks near the equator demonstrating to tourists that as they move back and forth across the equator the water drains either CW or CCW. It's a fun way for tourists to leave their cash behind. How the trick at the equator is performed is a puzzle I'll leave to others to figure out.
     
  15. Absane Rocket Surgeon Valued Senior Member

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  16. stereologist Escapee from Dr Moreau Registered Senior Member

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    Thanks for the video absane. That video is fairly old. I remember seeing it in school a long time ago.
     

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