Which one of the following statements about the Coriolis force is not correct ?
It deflects the wind to the right direction : in the southern hemisphere.
Understanding the Coriolis Force
The Coriolis force is an apparent force that acts on objects moving within a rotating reference frame. On Earth, this rotating reference frame is the planet itself. The Coriolis force significantly influences the movement of large-scale air and water masses, like winds and ocean currents.
Let's analyze each statement about the Coriolis force to determine which one is not correct.
Analysis of Statements on Coriolis Force Properties
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Statement 1: It is maximum at the Poles.
The magnitude of the Coriolis force is dependent on the speed of the object, the angular velocity of the Earth's rotation, and the sine of the latitude. The formula for the Coriolis force (per unit mass) is approximately:
\(F_c = 2v\Omega \sin(\phi)\)
Where:
- \(v\) is the speed of the object
- \(\Omega\) is the angular velocity of Earth's rotation
- \(\phi\) is the latitude
At the Poles (\(\phi = 90^{\circ}\) or \(-90^{\circ}\)), \(\sin(90^{\circ}) = 1\) and \(\sin(-90^{\circ}) = -1\). Since \(|\sin(\phi)|\) is maximum when \(|\phi| = 90^{\circ}\), the Coriolis force is maximum at the Poles. This statement is correct.
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Statement 2: It is absent at the Equator.
At the Equator (\(\phi = 0^{\circ}\)), \(\sin(0^{\circ}) = 0\). According to the formula \(F_c = 2v\Omega \sin(\phi)\), if \(\sin(\phi) = 0\), the Coriolis force is zero. Therefore, the Coriolis force is absent at the Equator. This statement is correct.
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Statement 3: It deflects the wind to the right direction : in the southern hemisphere.
The direction of deflection due to the Coriolis force depends on the hemisphere. In the Northern Hemisphere, the deflection is to the right of the direction of motion. In the Southern Hemisphere, the deflection is to the left of the direction of motion. This statement claims deflection is to the right in the Southern Hemisphere, which is incorrect.
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Statement 4: It deflects the wind to the right direction in the northern hemisphere.
As mentioned above, in the Northern Hemisphere, the Coriolis force deflects moving objects (like wind) to the right of their intended path. This statement is correct.
Based on the analysis, the statement that is not correct is the one claiming that the Coriolis force deflects the wind to the right in the Southern Hemisphere.
Summary of Coriolis Force Deflection
| Hemisphere | Direction of Deflection |
|---|---|
| Northern Hemisphere | To the right of motion |
| Southern Hemisphere | To the left of motion |
Therefore, the statement "It deflects the wind to the right direction : in the southern hemisphere." is incorrect.
Revision Table: Coriolis Force Facts
| Property | Description | Correct/Incorrect Statement |
|---|---|---|
| Magnitude at Poles | Maximum | Statement 1: Correct |
| Magnitude at Equator | Zero/Absent | Statement 2: Correct |
| Deflection in Northern Hemisphere | To the right | Statement 4: Correct |
| Deflection in Southern Hemisphere | To the left | Statement 3: Incorrect |
Additional Information on Coriolis Force
The Coriolis effect is more pronounced for large-scale phenomena like global winds, ocean currents, and the paths of hurricanes. It is generally negligible for small-scale, short-duration events like water draining from a sink, where other forces like viscosity and initial conditions are dominant.
This apparent force arises because a point on the Earth's surface travels faster at the Equator (larger radius of rotation) than at higher latitudes (smaller radius of rotation). As an object moves north or south, it carries its initial eastward velocity. If it moves towards a latitude with a different eastward velocity, the Coriolis effect acts to conserve angular momentum, resulting in the observed deflection.
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