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UPSC Prelims 2024 · World Geography · Oceans, Seas and Straits
With reference to “Coriolis force”, which of the following statements is/are correct?
- It increases with increase in wind velocity.
- It is maximum at the poles and is absent at the equator.
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Show the answer and explanation
Answer: (c) Both 1 and 2
Speed and latitude are the two terms in the Coriolis formula (2vΩ sinφ).
Statement by statement
1. ✓ CORRECT The Coriolis force is proportional to the speed of the moving air: faster wind, stronger deflection.
2. ✓ CORRECT It depends on the sine of the latitude: zero at 0° and greatest at 90°.
The idea
The Earth’s rotation deflects moving air and water to the right in the northern hemisphere and to the left in the southern. With no Coriolis force at the equator, winds can’t spin up — so cyclones don’t form within about 5° of it.
No Coriolis at 0° → no spin → no cyclones near the equator
Why the others are wrong
(a) Doubts the latitude effect. Coriolis depends on sin(latitude) — 0 at the equator, 1 at the pole.
(b) Doubts the speed link. The deflecting force grows with the velocity of the moving air.
(d) Would mean the force is the same everywhere — but then cyclones could form on the equator.
The trap
People remember “no Coriolis at the equator” but doubt the speed link. Both are in the same NCERT paragraph.
🔒 Coriolis ∝ wind speed × sin(latitude): zero at the equator, maximum at the poles; right in the north, left in the south.
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