Physics: Space Physics: UPSC Previous Year Questions (Science and Technology)
5 previous year UPSC Prelims questions on space physics appear here, from 1996 to 2008. UPSC asks why a comet’s tail points away from the Sun, what defines a black hole, how a jet engine differs from a rocket and what INSAT-4A does. The explanations give the physical reason in plain words.
Explanations state facts as of the year each question was asked; words like “recently” refer to that year.
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UPSC 2008Science and Technology · Physics: Space Physics
Q1. Consider the following statements in respect of a jet engine and a rocket: 1. A jet engine uses the surrounding air for its oxygen supply and so is unsuitable for motion in space. 2. A rocket carries its own supply of oxygen in the gas form, and fuel. Which of the statements given above is/are correct?
Explanation
Statement 1 is correct: A jet engine relies on the oxygen in the Earth’s atmosphere for combustion. In space, where there is no atmosphere, a jet engine cannot function because it cannot obtain the necessary oxygen for burning fuel.
Statement 2 is incorrect: Rockets do carry their own supply of oxygen, but typically, the oxygen is not in gas form. It is usually stored as a liquid oxidizer (e.g., liquid oxygen, LOX) along with the fuel.
UPSC 2006Science and Technology · Physics: Space Physics
Q2. Consider the following statements in respect of India advanced satellite INSAT-4A: 1. INSAT-4A was launched in December, 2005 from New Mexico. 2. The European Commercial Launch Service Provider Arianespace was associated with the launch of INSAT-4A. 3. Tata-Sky; a digital cable service provider; is associated with DTH television broadcasting service from INSAT-4A. Which of the statements given above are correct?
Explanation
Statement 1 is incorrect: INSAT-4A was launched on December 5, 2005, using an Ariane 5 rocket from Kourou, French Guiana (not New Mexico).
Statement 2 is correct: Arianespace was responsible for launching INSAT-4A using the Ariane 5 rocket, a major commercial launch vehicle used for heavy payloads like communication satellites.
Statement 3 is correct: Tata Sky, an Indian Direct-to-Home (DTH) service provider, uses the INSAT-4A satellite for providing satellite television services in India.
UPSC 2000Science and Technology · Physics: Space Physics
Q3. A ‘black hole’ is a body in space which does not allow any radiation to come out. This property is due to its:
Explanation
A black hole is a region in space where gravity is so intense that not even light or any form of radiation can escape from it. This extreme gravitational pull is a result of its very high density, as the mass of the black hole is compressed into a very small volume, creating a gravitational field strong enough to trap light and radiation. Event Horizon: The boundary around a black hole beyond which nothing, not even light, can escape due to the extreme gravitational pull. Singularity: The point at the center of a black hole where gravity is infinitely strong, and matter is thought to be crushed to an infinitely small point with infinite density. Schwarzschild Radius: The radius of the event horizon, which depends on the mass of the black hole. It defines the size of the black hole’s event horizon. Accretion Disk: A rotating disk of matter, such as gas and dust, that orbits a black hole. The matter in the disk heats up as it spirals toward the event horizon. Hawking Radiation: A theoretical prediction by physicist Stephen Hawking that black holes can emit radiation due to quantum effects near the event horizon, eventually leading to their slow evaporation.
UPSC 1997Science and Technology · Physics: Space Physics
Q4. The tail of a comet is directed away from the sun because:
Explanation
A comet is a small celestial body composed of ice, dust, and rocky material that orbits the Sun in an elliptical path. When it gets close to the Sun, the heat causes its icy nucleus to vaporize, forming a glowing coma.
Option (c) is correct: The tail of a comet is directed away from the Sun due to the solar wind and radiation pressure exerted by the Sun. The Sun emits charged particles (mainly electrons and protons) that interact with the comet’s nucleus and coma, pushing gas and dust away. This creates a glowing tail that always points opposite the Sun, regardless of the comet’s orientation. The tail’s direction can change as the comet moves, influenced by factors like solar wind intensity, the coma’s shape, and the Sun’s magnetic field.
UPSC 1996Science and Technology · Physics: Space Physics
Q5. Consider the following statements: A person in a spaceship located half way between the earth and the sun will notice that the: (1) The sky is jet black. (2) stars do not twinkle. (3) The temperature outside the spaceship is much higher than that on the surface of the earth. Of these statements:
Explanation
Statement 1 is correct: In space, there is no atmosphere to scatter sunlight, so the sky appears black, even during the day.
Statement 2 is correct: In space, stars appear as steady points of light because there is no atmospheric turbulence to cause them to twinkle, as we observe from Earth.
Statement 3 is correct: Space near the Sun is extremely hot, with temperatures rising significantly when exposed to direct sunlight. The spacecraft would experience extreme temperatures, which is why temperature regulation inside the spacecraft is essential for astronauts.
Answer key for these questions
Q
UPSC year
Correct answer
1
2008
(a) 1 only
2
2006
(c) 2 and 3 only
3
2000
(c) very high density
4
1997
(c) the radiation emitted by the sun exerts a radial pressure on the comet throwing its tail away from the sun
5
1996
(d) 1, 2 and 3 are correct
What UPSC has tested in Physics: Space Physics
The tail of a comet is directed away from the Sun because of the radiation and solar wind from the Sun.
A black hole does not allow any radiation to come out because of its very high density and gravity.
A jet engine uses oxygen from the atmosphere, while a rocket carries its own oxidiser.
Frequently asked questions
How many previous year UPSC questions are there on Physics: Space Physics?
This page covers 5 previous year UPSC Prelims GS Paper-I questions on Physics: Space Physics (Science and Technology), asked from 1996 to 2008. Each has the correct answer and an explanation.
Why does a comet’s tail point away from the Sun?
Because the Sun’s radiation pressure and the solar wind push the gas and dust released by the comet outward. The tail therefore always points away from the Sun, whichever way the comet is moving.
What is the difference between a jet engine and a rocket?
A jet engine takes in oxygen from the atmosphere to burn its fuel, so it works only within the atmosphere. A rocket carries its own oxidiser, so it can operate in space.
