Universe & Solar System – NDA Geography PYQs

NDA 2023-I

Q. 1. Which one of the following astronomers proved that the Earth and other planets revolve around the Sun?

(a) Copernicus

(b) Kepler

(c) Galileo

(d) Newton

Answer: (a) Copernicus

Explanation: Nicolaus Copernicus (1473–1543) proposed the heliocentric model: that the Earth and other planets revolve around the Sun: in his work “De Revolutionibus Orbium Coelestium” (1543). This was a revolutionary departure from the prevailing geocentric (Earth-centred) model of Ptolemy. Kepler later established the laws of planetary motion (elliptical orbits). Galileo used telescopic observations to support the heliocentric model. Newton explained WHY planets orbit (gravitational force). Copernicus was the first to formally propose the Sun-centred system for all planets. Concept Tested: Copernicus: proposed the heliocentric model (planets revolve around the Sun) in the 16th century

NDA 2021-II

Q. 2. Which one from among the following planets is largest in size?

(a) Earth

(b) Venus

(c) Mars

(d) Mercury

Answer: (a) Earth

Explanation: Among the four options: Earth, Venus, Mars, and Mercury: Earth is the largest. Approximate radii: Earth ~6,371 km, Venus ~6,052 km (~95% of Earth), Mars ~3,390 km, Mercury ~2,440 km. All four are inner (terrestrial) planets. Earth is the largest of the four inner planets. Concept Tested: Earth: largest among the four inner planets (Earth, Venus, Mars, Mercury) by size

NDA 2021-I

Q. 3. Which one of the following planets has the highest density?

(a) Mercury

(b) Venus

(c) Jupiter

(d) Earth

Answer: (d) Earth

Explanation: Among all eight planets, Earth has the highest average density: approximately 5.51 g/cm³. This is because Earth has a large iron-nickel core that contributes significantly to its overall density. For comparison: Mercury ~5.43 g/cm³, Venus ~5.24 g/cm³, Jupiter ~1.33 g/cm³ (gas giant: mostly hydrogen and helium, hence low density). Among the given options: Earth (~5.51) > Mercury (~5.43) > Venus (~5.24) > Jupiter (~1.33). Concept Tested: Earth: highest density among all planets (~5.51 g/cm³); gas giants have very low density

★ JOVIK Exam Insight Planet density ranking for NDA: Earth is the densest planet in the solar system. Gas giants (Jupiter, Saturn, Uranus, Neptune) have low densities because they are made mostly of gas. Saturn’s density (~0.69 g/cm³) is so low it would float on water! Rocky inner planets have much higher densities. Earth > Mercury > Venus > Mars for density among inner planets.

NDA 2019-I

Q. 4. Light year is a unit of measurement of:

(a) very large distances

(b) time interval in years

(c) amount of light received on Earth in a year

(d) mass of atoms

Answer: (a) very large distances

Explanation: The third time NDA tested the same concept: light year = distance. The light year is used in astronomy to express the vast distances between stars and galaxies. The fact that NDA has asked this exact question in three consecutive question sets (2017-II, 2018-I, 2019-I) makes it one of the highest-priority facts in this chapter. Concept Tested: Light year: very large distances (confirmed by NDA testing this three times in three consecutive papers)

Q. 5. ‘Black hole’ is a:

(a) huge black star which has zero acceleration due to gravity on its surface

(b) star which has moderate acceleration due to gravity on its surface

(c) star which has collapsed into itself and has large acceleration due to gravity on its surface

(d) star which has collapsed into itself and has zero acceleration due to gravity on its surface

Answer: (c) star which has collapsed into itself and has large acceleration due to gravity on its surface

Explanation: A black hole is the remnant of a massive star that has collapsed under its own gravity at the end of its life cycle. The key features of a black hole: 1. It has collapsed into itself (gravitational collapse). 2. It has an extremely strong gravitational field: so strong that not even light can escape from it (hence “black”). 3. The escape velocity at the event horizon equals the speed of light. So option (c) is correct: collapsed + large (very high) acceleration due to gravity. Concept Tested: Black hole: gravitationally collapsed star with extremely strong gravity (not zero gravity)

NDA 2018-I

Q. 6. Light year is a unit for measurement of:

(a) age of universe

(b) very small time intervals

(c) very high temperature

(d) very large distance

Answer: (d) very large distance

Explanation: This is the same concept as Q. 6 (NDA 2017-II). A light year measures very large distances in astronomy: the distances between stars and galaxies. For example: The nearest star (Proxima Centauri) is about 4.24 light years away. The Andromeda Galaxy is about 2.5 million light years away. Light year is NOT a time interval, temperature, or age measurement. Concept Tested: Light year: unit for measuring very large astronomical distances; same concept tested in NDA 2017-II and 2019-I

NDA 2017-II

Q. 7. Light year is a measure of:

(a) time

(b) distance

(c) total amount of light falling on the Earth in a year

(d) average luminosity

Answer: (b) distance

Explanation: A light year is the distance that light travels in one year in a vacuum. Since light travels at approximately 3 × 10⁸ metres per second, one light year = approximately 9.46 × 10¹⁵ metres (about 9.46 trillion km). Despite having “year” in the name, a light year is a unit of DISTANCE: not time. Concept Tested: Light year: unit of distance (distance light travels in one year ≈ 9.46 trillion km)

★ JOVIK Exam Insight Light year = distance, NOT time. This is one of the most repeated NDA traps. NDA has tested this in 2017-II, 2018-I, and 2019-I. All three times, the answer is distance. The word “year” makes students confuse it with time: but the “year” only tells you how long light travels for; the answer is the DISTANCE covered.

NDA 2015-I

Q. 8. The radius of the Moon is about one-fourth that of the Earth and acceleration due to gravity on the Moon is about one-sixth that on the Earth. From this, we can conclude that the ratio of mass of Earth to the mass of the Moon is about:

(a) 10

(b) 100

(c) 1,000

(d) 10,000

Answer: (b) 100

Explanation: Using the formula g = GM/R², we can write M = gR²/G. Given: R_moon = R_earth/4 and g_moon = g_earth/6. M_earth/M_moon = (g_earth × R_earth²) / (g_moon × R_moon²) = (g_earth × R_earth²) / ((g_earth/6) × (R_earth/4)²) = (g_earth × R_earth²) / (g_earth/6 × R_earth²/16) = 1 / (1/6 × 1/16) = 1 / (1/96) = 96 ≈ approximately 100. The ratio of Earth’s mass to Moon’s mass is approximately 81 (actual value), which rounds closest to 100 among the options given. Note: The source records answer (a), but option (a) = 10. The calculated value (~96) is closest to (b) 100. Verify against official NDA 2015-I key. Concept Tested: Mass ratio calculation: Earth’s mass to Moon’s mass using g and R relationships; result ≈ 81–96 (closest to 100)

NDA 2010-I

Q. 9. Which of the following statements is/are correct?

1. Lunar eclipse takes place when the Earth comes directly between the Sun and the Moon.

2. Solar eclipse happens when the Moon comes directly between the Sun and the Earth.

3. Lunar eclipse takes place when the Sun comes directly between the Earth and the Moon.

4. Solar eclipse happens when the Earth comes directly between the Sun and the Moon.

Select the correct answer using the code given below:

(a) 1, 2 and 3

(b) 3 and 4

(c) 1 and 2

(d) 2 only

Answer: (c) 1 and 2

Explanation: Statement 1: Correct. Lunar eclipse occurs when the Earth comes directly between the Sun and the Moon. Earth’s shadow falls on the Moon, darkening it. Statement 2: Correct. Solar eclipse occurs when the Moon comes directly between the Sun and the Earth. The Moon blocks the Sun’s light from reaching Earth. Statement 3: Incorrect. This describes the Sun between Earth and Moon, which is not the cause of a lunar eclipse (and would be impossible given the sizes/distances). Statement 4: Incorrect. The Earth between the Sun and Moon causes a LUNAR eclipse, not a solar eclipse. Concept Tested: Eclipse mechanisms: Lunar: Earth between Sun and Moon; Solar: Moon between Sun and Earth

★ JOVIK Exam Insight Eclipse logic for NDA: Think of the order of objects. Lunar eclipse: Sun → Earth → Moon (Earth blocks sunlight reaching the Moon). Solar eclipse: Sun → Moon → Earth (Moon blocks sunlight reaching Earth). A simple memory trick: in a Lunar eclipse, the L-moon loses light. In a Solar eclipse, the S-sun is blocked from view on Earth.

NDA 2009-I

Q. 10. Which among the following planets is smaller in size than the Earth?

(a) Neptune

(b) Venus

(c) Saturn

(d) Uranus

Answer: (b) Venus

Explanation: Among the eight planets, Earth is the fifth largest. Comparing with the options: Venus: radius ~6,052 km vs. Earth ~6,371 km. Venus is slightly smaller than Earth (~95% of Earth’s size). Correct answer. Neptune: radius ~24,622 km. Much larger than Earth. Saturn: radius ~58,232 km. Far larger than Earth. Uranus: radius ~25,362 km. Much larger than Earth. Only Venus (and Mars, Mercury: not in options) is smaller than Earth. Concept Tested: Venus: the only planet among the options smaller than Earth in size

★ JOVIK Exam Insight Planet size order (largest to smallest): Jupiter > Saturn > Uranus > Neptune > Earth > Venus > Mars > Mercury. For NDA, remember: Earth is 5th largest. Planets smaller than Earth: Mars and Venus (slightly), Mercury (much smaller). Planets larger: Jupiter, Saturn, Uranus, Neptune.

Q. 11. In which one of the following is a great dark plain called “Maria” found?

(a) Earth

(b) Mars

(c) Jupiter

(d) Moon

Answer: (d) Moon

Explanation: “Maria” (singular: “Mare”) are large, dark basaltic plains on the Moon formed by ancient volcanic eruptions. The word “Maria” is Latin for “seas”: early astronomers mistook these dark areas for actual seas. The most well-known example is the Mare Tranquillitatis (Sea of Tranquility), where Apollo 11 landed in 1969. Maria are not found on Earth, Mars (Mars has different geological features), or Jupiter (a gas giant). Concept Tested: Maria: dark basaltic plains on the Moon; Latin for “seas”; formed by ancient volcanism

NDA 2008-II

Q. 12. Which one of the following statements is/are correct with regard to the Milky Way?

1. It is a spiral galaxy.

2. The solar system resides in one of its spiral arms.

Select the correct answer using the code given below:

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer: (c) Both 1 and 2

Explanation: Statement 1: Correct. The Milky Way is a barred spiral galaxy. It contains hundreds of billions of stars arranged in a distinctive spiral structure with a central bulge and radiating arms. Statement 2: Correct. Our solar system is located in one of the Milky Way’s outer spiral arms: called the Orion Arm (or Orion Spur), situated between the Perseus Arm and the Sagittarius Arm. The solar system is approximately 26,000 light-years from the galactic centre. Concept Tested: Milky Way: spiral galaxy; solar system located in the Orion Arm, one of its spiral arms

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