Question 13 from UPSC CSE 2015 - Geography

Question

Tides occur in the oceans and seas due to which among the following?
1. Gravitational force of the Sun
2. Gravitational force of the Moon
3. Centrifugal force of the Earth
Select the correct answer using the code given below.

Accepted Answer

Correct Option: D. 1, 2, and 3

Strategy: Focus on which forces are physically responsible for tides. Both the Moon's and Sun's gravity pull on Earth's water, causing tides—so both Statement 1 and Statement 2 are correct. The centrifugal force arises because the Earth-Moon system revolves around a common center of mass, contributing to the tidal phenomenon. Recognizing this eliminates the options that exclude any term, leaving only the option with all three (option D).

Key Info: Tides are periodic oscillations in ocean and sea levels primarily caused by the gravitational pull of the Moon and, to a lesser extent, the Sun upon Earth's oceans.

- The Moon's gravity is the main driver of tides due to its proximity, causing bulges of water directly beneath it and on the opposite side (direct and opposite bulges). The Sun, though much more massive, exerts a lesser tidal force because of its greater distance, but still contributes significantly—especially during full and new moon phases, when solar and lunar pulls combine (spring tides).
- The centrifugal force in this context arises from the rotation of the Earth-Moon system around their common barycenter. This pseudo-force acts opposite to the Moon's pull, creating the second tidal bulge on the side of the Earth opposite the Moon.
- The interplay between these forces produces various types of tides: spring tides (when gravitational effects combine) and neap tides (when Sun and Moon are at right angles, partially canceling their tidal influences).
- Tidal phenomena are essential for navigation, marine life, coastal ecosystem dynamics, and have been studied for centuries. Major explanations rely upon Newton's law of gravitation and orbital mechanics. Advanced models also consider Earth's rotation, ocean basin shape, and local geographic features.

Answer

Option A: 1 only

Answer

Option B: 2 and 3 only

Answer

Option C: 1 and 3 only

Tides occur in the oceans and seas due to which among the following? Gravitational force of the Sun Gravitational force of the Moon Centrifugal force of the Earth Select the correct answer using the code given below.

Tides occur in the oceans and seas due to which among the following?

Gravitational force of the Sun

Gravitational force of the Moon

Centrifugal force of the Earth
Select the correct answer using the code given below.