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Q14 (IAS/2024) Geography › World Physical Geography › Atmospheric pressure winds Official Key

With reference to "Coriolis force", which of the following statements is/are correct ? 1. It increases with increase in wind velocity. 2. It is maximum at the poles and is absent at the equator. Select the answer using the code given below :

Result
Your answer: —  ·  Correct: C
Explanation

The correct answer is option C because both statements are correct.

The Coriolis force acting on a body increases with an increase in its velocity.[1] This relationship is also evident from the mathematical formula, where the magnitude (Coriolis force) of the effect is given by 2νω sin ϕ, in which ν is the velocity of the object, ω is the angular velocity of the Earth, and ϕ is the latitude.[2] Therefore, statement 1 is correct.

Regarding statement 2, the Coriolis force is zero at the equator but increases with latitude, reaching a maximum at the poles.[2] This is because at the equator, ϕ = 0° and at the poles, ϕ = 90°[2], and since the force depends on sin ϕ, it becomes zero at the equator (sin 0° = 0) and maximum at the poles (sin 90° = 1). Hence, statement 2 is also correct.

Since both statements accurately describe the characteristics of the Coriolis force, option C (Both 1 and 2) is the correct answer.

Sources
  1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Geostrophic Wind > p. 384
  2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Causes of The Coriolis Effect > p. 309
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Q. With reference to "Coriolis force", which of the following statements is/are correct ? 1. It increases with increase in wind velocity. 2…
At a glance
Origin: From standard books Fairness: High fairness Books / CA: 10/10 · 0/10

This is a classic 'Return on Investment' question directly from NCERT Class XI, Chapter 9. It proves that despite the hype around dynamic questions, static Climatology remains the backbone. If you missed this, you are neglecting the 'Forces Affecting Wind' section which is fundamental to understanding Cyclones and Jet Streams.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Does the magnitude of the Coriolis force increase with increasing wind velocity (i.e., is Coriolis force proportional to wind speed)?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Causes of The Coriolis Effect > p. 309
Presence: 5/5
“• The Coriolis effect is related to the motion of the object, the motion of the Earth, and the latitude. For this reason, the magnitude (Coriolis force) of the effect is given by 2νω sin ϕ, in which ν is the velocity of the object, ω is the angular velocity of the Earth, and ϕ is the latitude. At the equator, ϕ = 0° and at the poles, ϕ = 90°. Thus, the Coriolis force is zero at the equator but increases with latitude, reaching a maximum at the poles.”
Why this source?
  • Gives the quantitative expression F_C = 2 ν ω sin φ, where ν is the object's velocity — directly showing proportionality to speed.
  • Explicitly links the Coriolis magnitude to the motion of the object (wind) and latitude, making the velocity dependence central.
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Geostrophic Wind > p. 384
Presence: 5/5
“• The Coriolis force acting on a body increases with an increase in its velocity. The winds in the upper atmosphere, 2-3 km above the surface, are free from the frictional effect of the surface and are controlled by the pressure gradient and the Coriolis force. When isobars are straight, and when there is no friction, the pressure gradient force is balanced by the Coriolis force, and the resultant wind blows parallel to the isobar (deflection of the wind is maximum). This wind is known as the geostrophic wind. Why Don't Winds Flow from Tropical High-Pressure (In Upper Troposphere) To Polar Low (In Upper Troposphere) Directly as Shown in The Figure Below?”
Why this source?
  • Plainly states that the Coriolis force acting on a body increases with an increase in its velocity.
  • Applies this to fast upper‑air winds (jet streams), showing practical cases where higher speeds produce larger Coriolis effects.
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > UPSC Prelims 2011] Which one of the following weather conditions is indicated by a sudden fall in barometer reading? > p. 308
Presence: 4/5
“• Due to the earth's rotation, winds do not cross the isobars at right angles as the pressure gradient force directs but get deflected from their original path. This deviation is the result of the earth's rotation and is called the Coriolis effect. Due to this effect, winds in the northern hemisphere get deflected to the right of their path and those in the southern hemisphere to their left (Farrell's Law). This deflection force does not seem to exist until the air is set in motion and increases with wind velocity and an increase in latitude.”
Why this source?
  • States the deflection (Coriolis effect) increases with wind velocity and with latitude.
  • Connects increased pressure gradient → higher wind speed → larger deflection, reinforcing the speed dependence.
Statement 2
Is the Coriolis force absent at the equator and maximum at the geographic poles?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Causes of The Coriolis Effect > p. 309
Presence: 5/5
“• The Coriolis effect is related to the motion of the object, the motion of the Earth, and the latitude. For this reason, the magnitude (Coriolis force) of the effect is given by 2νω sin ϕ, in which ν is the velocity of the object, ω is the angular velocity of the Earth, and ϕ is the latitude. At the equator, ϕ = 0° and at the poles, ϕ = 90°. Thus, the Coriolis force is zero at the equator but increases with latitude, reaching a maximum at the poles.”
Why this source?
  • Provides the formula 2νω sin φ linking Coriolis magnitude to latitude and velocity
  • Explains that sin φ = 0 at φ = 0° (equator) so the force is zero, and is maximal at φ = 90° (poles)
  • Connects dependence to object velocity and Earth's angular velocity, making the latitude dependence explicit
FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 9: Atmospheric Circulation and Weather Systems > Coriolis Force > p. 79
Presence: 5/5
“to the left in the southern hemisphere. The deflection is more when the wind velocity is high. The Coriolis force is directly proportional to the angle of latitude. It is maximum at the poles and is absent at the equator. The Coriolis force acts perpendicular to the pressure gradient force. The pressure gradient force is perpendicular to an isobar. The higher the pressure gradient force, the more is the velocity of the wind and the larger is the deflection in the direction of wind. As a result of these two forces operating perpendicular to each other, in the low-pressure areas the wind blows around it.”
Why this source?
  • States Coriolis force is directly proportional to the angle of latitude
  • Explicitly asserts it is absent at the equator and maximum at the poles
  • Notes deflection increases with wind velocity, supporting magnitude variation with latitude
Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 12: Major Crops and Cropping Patterns in India > Biotic: Living > p. 105
Presence: 4/5
“Chorley, R.J. 1969, Water, Earth and Man, ed., London, Methuen. Coriolis Force: Te apparent defection of moving objects on Earth from a straight path, in relationship to the diferential speed of rotation at varying latitudes. Defection is to the right in the Northern Hemisphere and to the left in the Southern Hemisphere; it produces a maximum efect at the poles and zero efect along the equator. Crater: A circular surface or pipe; can be at the summit or on the fank of a volcano. Crust: Earth's outer shell of crystalline surface rock, ranging from 5 to 60 km in thickness from oceanic crust to mountain ranges.”
Why this source?
  • Describes zero effect along the equator and maximum effect at the poles
  • Links deflection direction in each hemisphere with a maximum at high latitudes
Pattern takeaway: UPSC is punishing candidates who skip the 'Mechanism' paragraphs in NCERTs. They didn't ask about the *result* (deflection direction); they asked about the *variables* (velocity/latitude). The pattern is a shift from 'What happens?' to 'Why/How it happens?'
How you should have studied
  1. [THE VERDICT]: Sitter. Directly lifted from NCERT Class XI (Fundamentals of Physical Geography), Chapter 9, under the heading 'Coriolis Force'.
  2. [THE CONCEPTUAL TRIGGER]: Climatology > Atmospheric Circulation > The 3 Forces governing Wind (Pressure Gradient, Coriolis, Frictional).
  3. [THE HORIZONTAL EXPANSION]: 1. Geostrophic Wind (PGF = Coriolis, flows parallel to isobars). 2. Frictional Force (reduces wind speed -> reduces Coriolis -> wind crosses isobars). 3. Ferrel's Law (Right in NH, Left in SH). 4. Buys Ballot's Law (Back to wind -> Low pressure on left in NH). 5. Cyclogenesis limit (No cyclones 0-5° latitude).
  4. [THE STRATEGIC METACOGNITION]: Don't just memorize the definition. Convert the text into a mental formula: F = 2vΩsinφ. This tells you immediately that Force (F) is proportional to Velocity (v) and Latitude (sinφ). This mathematical approach makes Statement 1 and 2 obvious without rote learning.
Concept hooks from this question
📌 Adjacent topic to master
S1
👉 Coriolis force proportionality & formula
💡 The insight

Coriolis force magnitude scales with the moving air's speed and is expressed as F_C = 2 ν ω sin φ (ν = velocity).

High‑yield for UPSC: enables direct answers to conceptual and quantitative questions on wind deflection, cyclone formation and upper‑air dynamics; links dynamics to latitude and angular velocity so candidates can solve balance and scaling problems.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Causes of The Coriolis Effect > p. 309
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Geostrophic Wind > p. 384
🔗 Anchor: "Does the magnitude of the Coriolis force increase with increasing wind velocity ..."
📌 Adjacent topic to master
S1
👉 Latitude dependence of Coriolis force
💡 The insight

Coriolis magnitude varies with latitude — zero at the equator and maximum at the poles — altering deflection for the same wind speed.

Essential for questions on regional wind patterns, cyclone genesis zones and global circulation cells; connects to topics like Hadley cells and why cyclones form away from the equator.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Causes of The Coriolis Effect > p. 309
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 26: Tropical Cyclones > Coriolis Force > p. 356
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 9: Atmospheric Circulation and Weather Systems > Coriolis Force > p. 79
🔗 Anchor: "Does the magnitude of the Coriolis force increase with increasing wind velocity ..."
📌 Adjacent topic to master
S1
👉 Geostrophic balance and role of friction
💡 The insight

When friction is negligible, pressure gradient and Coriolis forces balance to produce geostrophic winds; wind speed (and thus Coriolis) controls the balance and resulting flow direction.

Crucial for explaining jet streams, upper‑troposphere wind directions and deviations between surface and upper winds; helps answer how force balances determine wind flow relative to isobars.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Geostrophic Wind > p. 384
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Geostrophic Wind > p. 385
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 9: Atmospheric Circulation and Weather Systems > Forces Affecting the Velocity and Direction of Wind > p. 78
🔗 Anchor: "Does the magnitude of the Coriolis force increase with increasing wind velocity ..."
📌 Adjacent topic to master
S2
👉 Latitude dependence of Coriolis force (2Ωv sinφ)
💡 The insight

Coriolis magnitude varies with latitude following 2νω sin φ, making it zero at 0° and maximal at 90°.

High‑yield for explaining why wind deflection changes with latitude, why large‑scale atmospheric motions differ between equator and poles, and for solving dynamics problems that use the sinφ factor; links directly to formulas used in physical geography and meteorology questions.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Causes of The Coriolis Effect > p. 309
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 9: Atmospheric Circulation and Weather Systems > Coriolis Force > p. 79
🔗 Anchor: "Is the Coriolis force absent at the equator and maximum at the geographic poles?"
📌 Adjacent topic to master
S2
👉 Coriolis effect and tropical cyclogenesis latitude threshold
💡 The insight

Coriolis is required to impart rotation to developing storms, so cyclones cannot form at or too close to the equator.

Essential for questions on cyclone distribution and disaster geography (why cyclones form typically between ~5°–30° latitude), connects to monsoon and hazard topics, and helps eliminate incorrect options about cyclone formation near the equator.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 26: Tropical Cyclones > Coriolis Force > p. 356
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 28: Temperate Cyclones > 28.5. Tropical Cyclones vs. Temperate Cyclones > p. 408
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Why Tropical Cyclones Do Not Form At The Equator? > p. 310
🔗 Anchor: "Is the Coriolis force absent at the equator and maximum at the geographic poles?"
📌 Adjacent topic to master
S2
👉 Geostrophic balance: Coriolis vs pressure gradient
💡 The insight

Large‑scale winds aloft result from the balance between the pressure gradient force and the Coriolis force, producing geostrophic flow parallel to isobars.

Useful for explaining jet streams, upper‑air westerlies, and general circulation; equips aspirants to handle questions on wind patterns, pressure systems and balanced flow dynamics.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Geostrophic Wind > p. 384
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Upper Tropospheric Westerlies > p. 385
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 9: Atmospheric Circulation and Weather Systems > Coriolis Force > p. 79
🔗 Anchor: "Is the Coriolis force absent at the equator and maximum at the geographic poles?"
🌑 The Hidden Trap

Gradient Winds (Sub-geostrophic vs Super-geostrophic). Since they asked about straight-line Geostrophic logic, the next logical step is Curved Flow. Expect a question on why winds around a Low (Cyclone) are slower (Sub-geostrophic) than winds around a High (Anticyclone) for the same pressure gradient due to Centrifugal Force interaction.

⚡ Elimination Cheat Code

The 'Stationary Stone' Logic. Look at Statement 1. If Coriolis force did NOT increase with velocity, it would imply the force exists even when velocity is zero. Does a stationary stone on the ground get deflected sideways? No. Therefore, the force *must* depend on motion (velocity). Statement 1 is intuitively correct.

🔗 Mains Connection

Mains GS-3 (Internal Security/Defense): The Coriolis effect is a mandatory correction factor in Ballistics (Snipers, Artillery, ICBMs). A missile fired from a high latitude toward the equator will land west of its target without this correction. This links Physical Geography to Defense Technology.

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SIMILAR QUESTIONS

NDA-I · 2025 · Q91 Relevance score: 5.89

Which of the following statements with reference to Coriolis force is/are correct ? 1. Coriolis force acts perpendicular to the pressure gradient force 2. At the equator, the Coriolis force is zero and the wind blows perpendicular to the isobars Select the answer using the code given below :

CDS-I · 2021 · Q17 Relevance score: 4.34

Which one of the following statements about the Coriolis force is not correct ?

CDS-I · 2012 · Q72 Relevance score: 3.48

Consider the following state- ments : 1. Coriolis effect is zero at the Equator. 2. Coriolis effect is more towards the Poles. 3. Coriolis effects are related to the decreasing rotational velocity with increasing latitudes. 4. Coriolis effects are related to the increasing rotational velocity with increasing latitudes. Which of the statements given above are correct ?

CAPF · 2018 · Q51 Relevance score: 2.19

Which of the following statements about tropical cyclone are correct? 1. It originates and develops over warm oceanic surface. 2. Presence of Coriolis force is necesBajy for it. 3. It occurs in middle latitudinal region* 4. It develops ‘eye’ with calm and descending air condition. Select the correct answer using the code given below.

NDA-II · 2018 · Q6 Relevance score: 1.78

Statement I : Geostrophic wind blows above a height of 600 meters, parallel to the isobars Statement I : Geostrophic wind is the horizontal wind velocity, in which the coriolis force balances the horizontal pressure force.