Question map
Not attempted Correct Incorrect ★ Bookmarked
Loading…
Q41 (CDS-II/2008) Geography › World Physical Geography › Earth rotation and time Answer Verified

Assertion (A) : The Equatorial regions bulge outwards by about 21 kilometre compared to Poles. Reason (R) : Earth’s slow rotation reduces the effect of gravity around the Equator.

Result
Your answer: —  ·  Correct: A
Explanation

Assertion (A) is true as the Earth is an oblate spheroid, meaning it is flattened at the poles and bulges at the equator [c1][t3]. The equatorial radius is approximately 6,378 km, while the polar radius is about 6,357 km, resulting in a difference of roughly 21 km [t5][t6]. Reason (R) is also true and provides the correct explanation. The Earth's rotation generates a centrifugal force that is strongest at the equator [c1][c2]. This force acts outward, perpendicular to the axis of rotation, effectively opposing and reducing the net pull of gravity at the equatorial region [t1][t4]. This reduction in effective gravity allows the Earth's mass to settle into a shape where the equatorial region bulges outward until a gravitational and rotational equilibrium is reached [t1][t2]. Thus, the rotation-induced reduction in effective gravity directly causes the observed 21 km bulge.

Sources

  1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 18: Latitudes and Longitudes > The Shape of The Earth and Latitudinal Heat Zones > p. 241
  2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 7: Tectonics > Forces Behind The Drifting Of Continents (According to Wegener) > p. 95
  3. [3] https://pwg.gsfc.nasa.gov/stargaze/Srotfram1.htm
  4. [4] https://en.wikipedia.org/wiki/Equatorial_bulge
How others answered
Each bar shows the % of students who chose that option. Green bar = correct answer, blue outline = your choice.
Community Performance
Out of everyone who attempted this question.
67%
got it right
✓ Thank you! We'll review this.

SIMILAR QUESTIONS

CDS-I · 2006 · Q52 Relevance score: 1.56

Assertion (A): The salinity of oceans is relatively higher near the equator than at other regions. Reason (R): Equator region has heavy rainfall, high relative humidity and calm air.

NDA-I · 2009 · Q25 Relevance score: 1.26

Assertion (A) : The Equator is a great circle. Reason (R) : The Equator encircles the whole Earth and its plane divides the Earth into two equal halves.

NDA-II · 2016 · Q28 Relevance score: 1.22

The free fall acceleration g increases as one proceeds, at sea level, from the equator toward either pole. The reason is

IAS · 2002 · Q146 Relevance score: 0.60

Assertion (A) : 60°-65° latitudes in both the hemispheres have a low pressure belt instead of high pressure. Reason (R) : The low pressure areas are permanent over oceans rather than on land.

IAS · 2003 · Q113 Relevance score: 0.38

Assertion (A) : Areas lying within five to eight degrees latitude on either side of the equator receive rainfall throughout the year. Reason (R) : High temperatures and high humidity cause convectional rain to fall mostly in the afternoons near the equator.