UPSC NDA-1

21. Which one among the following is used in making gunpowder ?

Which one among the following is used in making gunpowder ?

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Magnesium sulphate
Potassium nitrate
Sodium stearate
Calcium sulphate
This question was previously asked in
UPSC NDA-1 – 2015
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The correct answer is Potassium nitrate. Potassium nitrate (KNO₃) is a key component of traditional black powder or gunpowder.
Gunpowder is typically a mixture of potassium nitrate (oxidizer), charcoal (fuel), and sulfur (fuel/stabilizer). Potassium nitrate serves as the oxidizer, providing oxygen for the rapid combustion of the fuel components.
Magnesium sulphate (Epsom salt) is used in medicine and baths. Sodium stearate is a major component of soap. Calcium sulphate (gypsum) is used in plaster and cement. None of these are components of traditional gunpowder.

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22. Which one among the following happens when a swing rises to a certain

Which one among the following happens when a swing rises to a certain height from its rest position ?

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Its potential energy decreases while kinetic energy increases
Its kinetic energy decreases while potential energy increases
Both potential and kinetic energy decrease
Both potential and kinetic energy increase
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UPSC NDA-1 – 2015
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The correct answer is Its kinetic energy decreases while potential energy increases. This describes the energy transformation as an object moves against gravity and slows down.
At the rest position (lowest point), the swing has its maximum speed and thus maximum kinetic energy (assuming negligible energy loss). As it rises, its height above the lowest point increases, causing its gravitational potential energy (PE = mgh) to increase. Simultaneously, the swing slows down as it moves upwards against gravity, causing its kinetic energy (KE = 1/2 mv^2) to decrease.
According to the principle of conservation of mechanical energy (in the absence of friction and air resistance), the total mechanical energy (sum of potential and kinetic energy) remains constant. Thus, any decrease in kinetic energy is compensated by an equal increase in potential energy, and vice versa.

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23. Optical fibres, though bent in any manner, allows light to pass throug

Optical fibres, though bent in any manner, allows light to pass through. What is the inference that one can draw from it ?

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The concept that light travels in straight path is wrong
Light can flow through the optical fibres
Light can travel through the fibres because of their ductility
Light can travel through the fibres due to multiple total internal reflections
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UPSC NDA-1 – 2015
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The correct answer is Light can travel through the fibres due to multiple total internal reflections. Optical fibres work based on the principle of Total Internal Reflection (TIR).
Optical fibres consist of a core (higher refractive index) surrounded by cladding (lower refractive index). Light entering the core at a suitable angle undergoes total internal reflection at the interface between the core and cladding, bouncing back into the core. This process repeats along the length of the fibre, guiding the light even when the fibre is bent, as long as the bend is not too sharp.
Option A is incorrect; light travels in straight lines in a homogeneous medium, but its path changes at interfaces or in non-homogeneous media. Option B is true but doesn’t explain the mechanism allowing travel through bends. Option C is irrelevant; ductility is a mechanical property, not an optical principle.

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24. If a charged particle (+q) is projected with certain velocity parallel

If a charged particle (+q) is projected with certain velocity parallel to the magnetic field, then it will

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trace helical path
trace circular path
continue its motion without any change
come to rest instantly
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UPSC NDA-1 – 2015
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The correct answer is continue its motion without any change. The magnetic force on a charged particle is given by the Lorentz force formula: F = q(v x B), where q is the charge, v is the velocity vector, and B is the magnetic field vector.
When the velocity vector (v) is parallel to the magnetic field vector (B), the cross product (v x B) is zero. Therefore, the magnetic force (F) on the charged particle is zero. With no force acting on it, the particle will continue to move in a straight line with constant velocity according to Newton’s first law of motion.
A charged particle traces a circular path when its velocity is perpendicular to a uniform magnetic field, and a helical path when its velocity has components both parallel and perpendicular to the field. A magnetic field alone does no work on a charged particle, only changes its direction of motion (unless the velocity is parallel or anti-parallel to the field).

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25. All life forms contain “molecules of life”. These are

All life forms contain “molecules of life”. These are

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Carbohydrates
Proteins
Nucleic acids
All of the above
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UPSC NDA-1 – 2015
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The correct answer is All of the above. Carbohydrates, Proteins, and Nucleic acids (DNA and RNA) are fundamental classes of organic macromolecules essential for all known forms of life.
These three types of molecules play crucial roles: Carbohydrates are primary energy sources and structural components; Proteins perform a vast array of functions including enzymes, structural support, and transport; Nucleic acids carry genetic information (DNA) and are involved in protein synthesis (RNA). Lipids are also often considered a fourth major class of biomolecules.
These macromolecules are built from smaller repeating units (monomers): carbohydrates from monosaccharides, proteins from amino acids, and nucleic acids from nucleotides. Their presence and interactions are fundamental to cellular structure and function.

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26. Energy is required for maintenance of life. It is obtained by a proces

Energy is required for maintenance of life.
It is obtained by a process called

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Metabolism
Phagocytosis
Photorespiration
Decomposition
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The correct answer is Metabolism. Metabolism encompasses all the chemical processes that occur within a living organism to maintain life, including those that generate energy.
Metabolism includes catabolic pathways which break down complex molecules (like carbohydrates, fats, proteins) obtained from food, releasing energy in the process (primarily in the form of ATP) that is used for cellular activities and maintenance of life.
Phagocytosis is a process of engulfing particles; Photorespiration is a process in plants that reduces photosynthetic efficiency; Decomposition is the breakdown of dead organic matter. While these processes are related to obtaining or releasing energy in specific contexts, Metabolism is the general term for the sum of biochemical reactions within an organism that yield energy for life functions.

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27. The newly formed state of Telengana is surrounded by

The newly formed state of Telengana is surrounded by

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5 States
4 States
6 States
3 States
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The correct answer is 5 States. Telangana is bordered by five other Indian states.
The states bordering Telangana are Maharashtra, Chhattisgarh, Odisha, Andhra Pradesh, and Karnataka. Counting these states confirms that Telangana shares its border with exactly five states.
Telangana was carved out of Andhra Pradesh and officially formed on June 2, 2014. Its borders were defined relative to the existing administrative divisions of Andhra Pradesh at that time. Understanding state boundaries is a basic aspect of Indian geography.

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28. Which one of the following statements is not correct ?

Which one of the following statements is not correct ?

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Kerala is the largest producer of natural rubber in India
Neyveli is an important thermal power generating area of Tamil Nadu
Ratnagiri Bauxite mining area is located in Karnataka
Assam is the largest tea producing state in India
This question was previously asked in
UPSC NDA-1 – 2015
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The correct option is C. The statement that Ratnagiri Bauxite mining area is located in Karnataka is not correct.
Let’s examine each statement:
A) Kerala is the largest producer of natural rubber in India. This statement is correct. Kerala dominates natural rubber production in India.
B) Neyveli is an important thermal power generating area of Tamil Nadu. This statement is correct. Neyveli has significant lignite reserves used to fuel large thermal power plants.
C) Ratnagiri Bauxite mining area is located in Karnataka. This statement is incorrect. Ratnagiri is a district in Maharashtra, known for its bauxite deposits and mining activities.
D) Assam is the largest tea producing state in India. This statement is correct. Assam is renowned for its tea production and is the leading state in India for tea output.
The question asks for the statement that is NOT correct. Based on the facts, statement C is incorrect as Ratnagiri bauxite mining is associated with Maharashtra, not Karnataka.

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29. Match List I with List II and select the correct answer using the code

Match List I with List II and select the correct answer using the code given below the Lists :

List I
(Compound)		 List II
(Nature)
A. Sodium hydroxide 1. Strong acid
B. Calcium oxide 2. Alkali
C. Acetic acid 3. Weak acid
D. Hydrochloric acid 4. Base

Code :

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A-2, B-3, C-4, D-1
A-2, B-4, C-3, D-1
A-1, B-4, C-3, D-2
A-1, B-3, C-4, D-2
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UPSC NDA-1 – 2015
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The correct option is B. The correct match is A-2, B-4, C-3, D-1.
Let’s classify each compound:
A. Sodium hydroxide (NaOH): NaOH is a strong base. Soluble bases are called alkalis. NaOH is highly soluble and completely dissociates in water, making it a strong alkali. Matches with 2 (Alkali).
B. Calcium oxide (CaO): CaO is a metal oxide. Metal oxides are generally basic in nature. When dissolved in water, it forms calcium hydroxide (Ca(OH)₂), a base. Thus, CaO is a base (basic oxide). Matches with 4 (Base).
C. Acetic acid (CH₃COOH): This is an organic acid (carboxylic acid). It is a weak acid because it does not completely dissociate in water. Matches with 3 (Weak acid).
D. Hydrochloric acid (HCl): HCl is a mineral acid. It is a strong acid because it completely dissociates in water. Matches with 1 (Strong acid).
Mapping the compounds to their nature:
A. Sodium hydroxide (NaOH) → 2. Alkali
B. Calcium oxide (CaO) → 4. Base
C. Acetic acid (CH₃COOH) → 3. Weak acid
D. Hydrochloric acid (HCl) → 1. Strong acid
Comparing this mapping with the options provided, option B matches correctly.

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30. Which one of the following is not a result of surface tension ?

Which one of the following is not a result of surface tension ?

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Nearly spherical drop of rain
Capillary rise
Removal of dirt by soap or detergent
Flow of a liquid
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UPSC NDA-1 – 2015
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The correct option is D. Flow of a liquid is not a result of surface tension.
Surface tension is a property of the surface of a liquid that allows it to resist an external force due to the cohesive nature of water molecules. It causes liquid surfaces to behave like stretched elastic membranes.
A) Nearly spherical drop of rain: Surface tension minimizes the surface area of the liquid, and a sphere has the minimum surface area for a given volume. This is a direct result of surface tension.
B) Capillary rise: This phenomenon, where a liquid rises in a narrow tube, is caused by the combined effects of surface tension and adhesion between the liquid and the tube walls. Surface tension contributes to the upward force.
C) Removal of dirt by soap or detergent: Soaps reduce the surface tension of water. This reduced surface tension allows the water to wet fabrics and dirt particles more effectively, helping in their removal. While it involves the *change* in surface tension, the ability to remove dirt in this way is linked to the surface properties facilitated by the detergent’s effect on surface tension.
D) Flow of a liquid: The bulk flow of a liquid (like water flowing in a pipe or a river) is driven by pressure differences or gravity, and it is resisted by viscosity. Surface tension primarily affects the liquid-air interface and phenomena occurring there (like drop formation, ripples), but it is not the fundamental cause or main characteristic of the bulk flow itself.
While surface tension might have secondary effects on flow dynamics (e.g., influencing the shape of a liquid jet), the primary forces driving and resisting bulk liquid flow are pressure gradients, gravity, and viscosity, not surface tension.

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