UPSC NDA-1 Archives

21. A 5 N force is defined when a mass of 10 kg is accelerated with

A 5 N force is defined when a mass of 10 kg is accelerated with

[amp_mcq option1=”5.0 cm/s²” option2=”0.5 m/s²” option3=”0.5 cm/s²” option4=”5.0 m/s²” correct=”option2″]

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This question requires the application of Newton’s Second Law of Motion, which states that Force (F) equals mass (m) times acceleration (a), or F = ma. We are given the force (F = 5 N) and the mass (m = 10 kg) and asked to find the acceleration (a) with which the mass is accelerated by this force. Rearranging the formula, we get a = F/m. Plugging in the given values: a = 5 N / 10 kg. Recalling that 1 Newton (N) is defined as 1 kg⋅m/s², the units work out correctly: a = (5 kg⋅m/s²) / 10 kg = 0.5 m/s². Checking the options, 0.5 m/s² corresponds to option B.

Newton’s Second Law (F=ma) is fundamental in relating force, mass, and acceleration. Ensure consistent units (SI units like Newtons, kilograms, and meters per second squared).

Option A (5.0 cm/s²) is 0.05 m/s², Option C (0.5 cm/s²) is 0.005 m/s², and Option D (5.0 m/s²) is significantly larger than the calculated value. It’s important to be careful with unit conversions (cm to m).

22. A mass M is dragged by a pulley on a horizontal plane by a force anti-

A mass M is dragged by a pulley on a horizontal plane by a force anti-parallel to its displacement. The work done in pulling the mass M is

[amp_mcq option1=”zero” option2=”positive” option3=”infinite” option4=”negative” correct=”option4″]

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Work done (W) is calculated as the dot product of force (F) and displacement (d): W = F ⋅ d = |F| |d| cos(θ), where θ is the angle between the force vector and the displacement vector. The problem states that the force is “anti-parallel” to its displacement. This means the force and displacement vectors are in opposite directions, so the angle between them is 180 degrees. The cosine of 180 degrees (cos(180°)) is -1. Therefore, the work done is W = |F| |d| (-1) = -|F| |d|. Since the magnitude of force and displacement are positive, the work done is negative.

Work done is negative when the force and displacement are in opposite directions (anti-parallel).

Work done is positive when the force and displacement are in the same direction (parallel, θ=0°, cos(0°)=1). Work done is zero when the force is perpendicular to the displacement (θ=90°, cos(90°)=0).

23. The twinkling of a star is due to the atmospheric

The twinkling of a star is due to the atmospheric

[amp_mcq option1=”diffraction of starlight” option2=”reflection of starlight” option3=”refraction of starlight” option4=”dispersion of starlight” correct=”option3″]

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The twinkling of stars is caused by the atmospheric refraction of starlight. As starlight passes through the Earth’s atmosphere, which has layers of varying density and temperature, it undergoes continuous refraction. The turbulent movement of air causes fluctuations in the refractive index of the atmosphere along the path of light. This leads to variations in the apparent position and intensity (brightness) of the star as perceived by an observer, resulting in the twinkling effect.

Atmospheric refraction causes starlight to bend as it passes through layers of air with different optical densities, leading to fluctuations in apparent brightness and position.

Planets are closer to Earth than stars and appear as extended sources rather than point sources. The light from planets undergoes similar refraction but the effect is averaged out over their larger apparent disk, which is why planets typically do not twinkle.

24. Which one of the following is caused by a bacterial pathogen?

Which one of the following is caused by a bacterial pathogen?

[amp_mcq option1=”AIDS” option2=”Dengue fever” option3=”COVID-19″ option4=”Typhoid fever” correct=”option4″]

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Typhoid fever is caused by the bacterium *Salmonella Typhi*. AIDS is caused by the Human Immunodeficiency Virus (HIV). Dengue fever is caused by the Dengue virus. COVID-19 is caused by the SARS-CoV-2 virus. Therefore, Typhoid fever is the only disease among the options caused by a bacterial pathogen.

Pathogens can be viruses, bacteria, fungi, or parasites. It is important to know the type of pathogen causing common diseases.

Typhoid fever is typically spread through contaminated food or water. It is a serious illness characterized by high fever, fatigue, abdominal pain, and sometimes a rash. Antibiotics are used to treat bacterial infections like typhoid fever.

25. Which one of the following groups is called ‘amphibians of plant

Which one of the following groups is called ‘amphibians of plant kingdom’?

[amp_mcq option1=”Bryophytes” option2=”Thallophytes” option3=”Pteridophytes” option4=”Gymnosperms” correct=”option1″]

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Bryophytes, which include mosses, liverworts, and hornworts, are often referred to as the ‘amphibians of the plant kingdom’. This is because, while they are terrestrial plants inhabiting damp environments, they are dependent on water for fertilization. The male gametes (sperms) of bryophytes are motile and require a film of water to swim to the egg cell. This dependence on water for reproduction is analogous to how amphibians (like frogs) live on land but require water for breeding.

Bryophytes require water for sexual reproduction, linking their life cycle to moist environments, hence the term ‘amphibians of the plant kingdom’.

Thallophytes is an older, artificial grouping. Pteridophytes (ferns) are vascular plants that also require water for fertilization, but bryophytes represent an earlier evolutionary step towards land plants and are more strongly associated with this term. Gymnosperms and Angiosperms are fully terrestrial and do not require external water for fertilization (pollen is transferred by wind, insects, etc.).

26. Which one of the following belongs to ‘Pisces’?

Which one of the following belongs to ‘Pisces’?

[amp_mcq option1=”Dogfish” option2=”Jellyfish” option3=”Silverfish” option4=”Starfish” correct=”option1″]

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‘Pisces’ is a traditional classification group that includes all fish. Dogfish (a type of shark) is a cartilaginous fish belonging to the class Chondrichthyes, which falls under Pisces. Jellyfish belong to the phylum Cnidaria, Silverfish are insects belonging to the phylum Arthropoda, and Starfish belong to the phylum Echinodermata. None of Jellyfish, Silverfish, or Starfish are fish (Pisces).

Pisces includes all true fish (aquatic vertebrates with gills, fins, and typically scales). Many organisms with “fish” in their name are not true fish.

The term ‘Pisces’ is often used as a superclass encompassing the classes Chondrichthyes (cartilaginous fish) and Osteichthyes (bony fish), and sometimes the jawless fishes (Agnatha). Modern classification often replaces Pisces with specific classes like Chondrichthyes, Actinopterygii, Sarcopterygii, etc.

27. In aquatic plants, large air sacs give them buoyancy effects. These sa

In aquatic plants, large air sacs give them buoyancy effects. These sacs are surrounded by which one of the following types of tissues?

[amp_mcq option1=”Parenchyma” option2=”Collenchyma” option3=”Sclerenchyma” option4=”Complex tissue” correct=”option1″]

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In aquatic plants, large air sacs or cavities that provide buoyancy are modifications of parenchyma tissue. This specialized parenchyma tissue with extensive intercellular air spaces is called aerenchyma. Aerenchyma facilitates gas exchange in submerged tissues and provides buoyancy, allowing the plant to float or remain upright in water.

Aerenchyma, a type of parenchyma tissue characterized by large air spaces, provides buoyancy and aids gas exchange in aquatic plants.

Collenchyma provides mechanical support to growing parts of the plant. Sclerenchyma provides rigid support and mechanical strength to mature parts of the plant. Complex tissues like xylem and phloem are responsible for transport of water, minerals, and food.

28. Which one of the following statements about ‘vacuoles’ is not correct?

Which one of the following statements about ‘vacuoles’ is not correct?

[amp_mcq option1=”In plants, there is a large central vacuole that may occupy 90% of total cell volume.” option2=”In plant cells, vacuoles provide turgidity and rigidity.” option3=”In Amoeba, vacuoles have role in nutrition.” option4=”Vacuoles are absent in animal cells.” correct=”option4″]

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Statement D is incorrect. Vacuoles are indeed present in animal cells, although they are generally smaller, more numerous, and less prominent than the large central vacuole found in mature plant cells. Animal cell vacuoles can perform various functions, including storage, waste disposal, protection, and growth. Statements A, B, and C are correct descriptions of vacuole functions in plants and some protists like Amoeba.

Vacuoles are present in both plant and animal cells, but their size and primary functions differ significantly.

In plant cells, the large central vacuole helps maintain turgor pressure, provides structural support, stores water, ions, nutrients, and waste products. In Amoeba, contractile vacuoles are crucial for osmoregulation, and food vacuoles are formed during phagocytosis for digestion.

29. Which one of the following plant plastids stores starch, oil and prote

Which one of the following plant plastids stores starch, oil and protein granules?

[amp_mcq option1=”Chloroplast” option2=”Leucoplast” option3=”Chromoplast” option4=”Xanthoplast” correct=”option2″]

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Leucoplasts are colourless plastids found in plant cells. They are primarily involved in the storage of various nutrients. Different types of leucoplasts are specialized for storing specific substances: amyloplasts store starch, elaioplasts store oils or fats, and aleuroplasts (or proteinoplasts) store proteins. The question asks for a plastid that stores starch, oil, and protein granules, and leucoplast is the general category that includes these specific storage plastids.

Leucoplasts are storage plastids in plant cells, specialized for storing starch, oils, and proteins.

Chloroplasts contain chlorophyll and are the sites of photosynthesis. Chromoplasts contain carotenoid pigments (like carotenes and xanthophylls) and give colour to flowers and fruits. Xanthoplast is a type of chromoplast containing yellow pigments (xanthophylls).

30. Which of the following statements about living and non-living being is

Which of the following statements about living and non-living being is/are correct?

1. While living being can demonstrate growth and repair, non-living being cannot.
2. While living being demonstrates metabolic processes, non-living being does not.

Select the correct answer using the code given below.

[amp_mcq option1=”1 only” option2=”2 only” option3=”Both 1 and 2″ option4=”Neither 1 nor 2″ correct=”option3″]

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Statement 1 is correct. Living beings demonstrate intrinsic growth (increase in mass and size from within, often through cell division) and have mechanisms for repair of damaged tissues and cells. Non-living things can increase in size, but this growth is typically extrinsic (accumulation of material on the surface), and they do not have biological repair mechanisms. Statement 2 is correct. Metabolism, the sum of all chemical processes that occur within a living organism in order to maintain life, is a defining characteristic of living beings. Non-living things do not perform metabolic processes.

Growth in living organisms is an internal process, while growth in non-living matter is external accumulation. Metabolism is a unique feature of living organisms.

While growth alone cannot be considered a defining property of living organisms because of non-living growth (like crystal formation), growth accompanied by other properties like metabolism, reproduction, response to stimuli, etc., distinguishes living beings.