UPSC NDA-1

41. Suppose there are two planets, 1 and 2, having the same density but th

Suppose there are two planets, 1 and 2, having the same density but their radii are R₁ and R₂ respectively, where R₁ > R₂. The accelerations due to gravity on the surface of these planets are related as

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[amp_mcq option1=”g₁ > g₂” option2=”g₁ < g₂" option3="g₁ = g₂" option4="Can't say anything" correct="option1"]

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If two planets have the same density but different radii R₁ and R₂ with R₁ > R₂, the acceleration due to gravity on the surface of the planet with the larger radius (Planet 1) will be greater than that on the surface of the planet with the smaller radius (Planet 2), i.e., g₁ > g₂.
– The acceleration due to gravity on the surface of a sphere is given by g = GM/R², where G is the gravitational constant, M is the mass, and R is the radius.
– The mass M can be expressed as M = ρ * V, where ρ is the density and V is the volume. For a sphere, V = (4/3)πR³.
– Substituting this into the gravity formula: g = G * (ρ * (4/3)πR³) / R² = (4/3)πGρR.
– Since the density ρ and constants G, 4/3, and π are the same for both planets, the acceleration due to gravity is directly proportional to the radius (g ∝ R).
– Given R₁ > R₂, it follows that g₁ > g₂.
This relationship shows that for objects of the same density, larger objects exert stronger gravitational pull at their surface compared to smaller objects. This is because the increase in mass (proportional to R³) outpaces the increase in distance from the center (proportional to R²).

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42. Tooth enamel is made up of which one of the following calcium

Tooth enamel is made up of which one of the following calcium compounds?

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Calcium carbonate
Calcium sulphate
Calcium hydroxide
Calcium phosphate
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Tooth enamel is primarily made up of calcium phosphate in the form of crystalline hydroxyapatite.
– Tooth enamel is the outermost protective layer of the tooth.
– It is the hardest substance in the human body, mainly due to its high mineral content.
– The main mineral component is hydroxyapatite, which is a complex form of calcium phosphate with the chemical formula Ca₅(PO₄)₃(OH).
While calcium phosphate is the general type of compound, the specific crystalline structure is hydroxyapatite. Other forms of calcium phosphate exist, but hydroxyapatite is the key mineral in bones and teeth. Acids produced by bacteria in the mouth can dissolve the hydroxyapatite crystals, leading to tooth decay. Fluoride can help strengthen enamel by incorporating into the crystal structure, forming fluoroapatite, which is less soluble in acid.

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43. What is the time gap in occurrence of two successive tides at a given

What is the time gap in occurrence of two successive tides at a given place on the ocean surface?

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12 hours
12 hours 26 minutes
24 hours
24 hours 52 minutes
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The time gap between the occurrence of two successive tides (e.g., two high tides or two low tides) at a given place on the ocean surface is approximately 12 hours and 26 minutes.
– Tides are primarily caused by the gravitational pull of the Moon and, to a lesser extent, the Sun.
– The Earth completes a rotation relative to the Sun in 24 hours (a solar day).
– However, the Moon also orbits the Earth in the same direction as Earth’s rotation. For a point on Earth to return to the same position relative to the Moon, it takes slightly longer than a solar day, approximately 24 hours and 50 minutes (a lunar day).
– There are usually two high tides and two low tides in one lunar day (semidiurnal tides).
– Therefore, the time between two successive high tides (or low tides) is about half a lunar day, which is approximately 12 hours and 25 minutes or 12 hours and 26 minutes.
The actual timing and amplitude of tides at any given location can be influenced by various factors, including the alignment of the Sun and Moon (leading to spring and neap tides), the shape of the coastline, and the depth of the water.

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44. Which one of the following ocean currents is NOT a cold ocean current?

Which one of the following ocean currents is NOT a cold ocean current?

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Canary current
California current
Kuroshio current
Oyashio current
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The Kuroshio current is a warm ocean current, while the Canary current, California current, and Oyashio current are cold ocean currents.
– Warm ocean currents generally flow from equatorial regions towards the poles, carrying warmer water.
– Cold ocean currents generally flow from polar regions towards the equator, carrying colder water.
– The Kuroshio is a strong western boundary current in the North Pacific, similar to the Gulf Stream in the Atlantic, bringing warm water northwards.
– The Canary and California currents are eastern boundary currents that flow southwards, carrying cooler water.
– The Oyashio is a subpolar current flowing south from the Bering Sea, bringing cold water to the North Pacific.
Ocean currents play a crucial role in distributing heat around the globe, influencing regional climates, marine ecosystems, and weather patterns. Western boundary currents like the Kuroshio are typically warm, deep, fast, and narrow, while eastern boundary currents like the California and Canary currents are typically cold, shallow, slow, and wide.

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45. Consider the following statements relating to Richter scale: 1. It w

Consider the following statements relating to Richter scale:

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  • 1. It was devised in 1935 by Charles F. Richter
  • 2. It describes the quantity of energy released by a single earthquake
  • 3. Richter Scale has no upper limit

Which of the statements given above is/are correct?

1 only
1 and 2 only
2 and 3 only
1, 2 and 3
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All three statements regarding the Richter scale are considered correct in the context of this question.
– Statement 1: The Richter magnitude scale was indeed devised by Charles F. Richter in 1935, along with Beno Gutenberg.
– Statement 2: The Richter scale measures the magnitude of an earthquake, which is directly related to the energy released. While the scale is based on the amplitude of seismic waves, magnitude is a logarithmic measure from which the quantity of energy released can be estimated.
– Statement 3: Theoretically, the Richter scale does not have an upper limit in its mathematical definition. Although practical measurement limitations existed with the original instruments for very large earthquakes, the scale itself isn’t bounded.
The Richter scale is a logarithmic scale; each whole number increase in magnitude represents a tenfold increase in wave amplitude and approximately a 32-fold increase in the energy released. For large earthquakes, the Moment Magnitude Scale (Mw) is now preferred as it is more directly related to the total energy released and does not suffer from saturation effects like the Richter scale at high magnitudes.

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46. Which one of the following is the correct sequence of proved coal rese

Which one of the following is the correct sequence of proved coal reserves in the Indian States in decreasing order ?

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Jharkhand, Chhattisgarh, Odisha, West Bengal
Jharkhand, Odisha, Chhattisgarh, West Bengal
Odisha, West Bengal, Jharkhand, Chhattisgarh
Odisha, Chhattisgarh, West Bengal, Jharkhand
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Based on the proved coal reserves data for Indian states, the correct sequence in decreasing order is Odisha, Chhattisgarh, West Bengal, and Jharkhand.
– Odisha holds the largest share of proved coal reserves in India, followed by Chhattisgarh.
– While Jharkhand has the largest share of *total* coal reserves (including proved, indicated, and inferred), its share of *proved* reserves is typically lower than Odisha and Chhattisgarh and often falls below West Bengal as well depending on the data source and year.
India has significant coal reserves. The distribution across states is a key aspect of its energy geography. Coal reserve data is periodically updated by agencies like the Geological Survey of India (GSI) and the Ministry of Coal. The terms proved, indicated, and inferred refer to the degree of geological assurance of the existence and recoverability of the reserves. Proved reserves have the highest degree of certainty.

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47. Which one of the following is an example of Salt-Crystal growth ?

Which one of the following is an example of Salt-Crystal growth ?

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Chemical weathering
Physical weathering
Biological weathering
Bio-chemical weathering
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Salt-crystal growth is a form of mechanical weathering (also known as physical weathering) where salts crystallize within the pores and cracks of rocks.
– Salt crystallization occurs when saline water evaporates, leaving salt crystals behind.
– As these crystals grow, they exert pressure on the surrounding rock, causing it to disintegrate.
– This process is particularly effective in arid and semi-arid regions where evaporation rates are high, and in coastal areas exposed to salt spray.
Physical weathering breaks down rocks into smaller pieces without changing their chemical composition. Other examples of physical weathering include frost wedging, thermal expansion and contraction, exfoliation, and abrasion. Chemical weathering involves chemical changes in the rock composition (e.g., dissolution, oxidation, hydrolysis). Biological weathering involves the action of living organisms. Bio-chemical weathering is a combination of biological and chemical processes.

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48. Which one of the following substances is NOT a mixture ?

Which one of the following substances is NOT a mixture ?

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Ice
Ice-cream
Air
Honey
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Ice is NOT a mixture.
A mixture is a substance comprising two or more components that are not chemically bonded.
Ice is the solid state of water (H₂O). Water is a chemical compound, meaning it is formed from different elements (Hydrogen and Oxygen) chemically combined in a fixed ratio. A compound is considered a pure substance.
Ice-cream is a mixture of water, milk solids, sugars, fats, flavorings, and air.
Air is a mixture of gases, primarily nitrogen, oxygen, argon, and carbon dioxide.
Honey is a mixture consisting mainly of sugars and water, along with other components like enzymes, minerals, etc.
Pure substances have a fixed composition and definite physical and chemical properties (like melting point, boiling point). Mixtures have variable compositions, and their properties depend on the proportions of the components. Ice (pure water) has a definite melting point (0°C at standard pressure), whereas mixtures like ice-cream, air, and honey do not melt/freeze or boil at a single fixed temperature but over a range.

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49. Which one of the following will NOT produce carbon dioxide on reacting

Which one of the following will NOT produce carbon dioxide on reacting with an aqueous solution of hydrochloric acid ?

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Limestone
Quick Lime
Chalk
Marble
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Quick Lime will NOT produce carbon dioxide on reacting with an aqueous solution of hydrochloric acid.
Hydrochloric acid (HCl) reacts with carbonates (like in Limestone, Chalk, and Marble, which are primarily CaCO₃) to produce carbon dioxide gas, a salt, and water. The reaction is: CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g).
Quick Lime is calcium oxide (CaO). Calcium oxide is a basic oxide. When it reacts with water, it forms calcium hydroxide (Ca(OH)₂, slaked lime). Calcium hydroxide then reacts with hydrochloric acid in a neutralization reaction: Ca(OH)₂(aq) + 2HCl(aq) → CaCl₂(aq) + 2H₂O(l). This reaction produces calcium chloride (a salt) and water, but no carbon dioxide. Alternatively, if CaO reacts directly with HCl without forming Ca(OH)₂ first (e.g., if HCl solution is added directly to solid CaO), the reaction is CaO(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l), again producing salt and water, but no CO₂.
Substances containing carbonate or bicarbonate ions will react with acids to produce carbon dioxide. Oxides and hydroxides react with acids in neutralization reactions, typically producing salt and water.

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50. On exposure to moist air, copper gains a green coat on its surface due

On exposure to moist air, copper gains a green coat on its surface due to formation of which one of the following compounds ?

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Copper carbonate
Copper oxide
Copper sulphate
Copper nitrate
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On exposure to moist air, copper gains a green coat on its surface due to the formation of copper carbonate (more specifically, basic copper carbonate).
When copper is exposed to moist air containing carbon dioxide, it reacts to form a complex mixture of copper carbonates and hydroxides, often referred to as patina. The simplified reaction involves copper reacting with oxygen, water, and carbon dioxide to form basic copper carbonate, typically Cu₂(OH)₂CO₃ (malachite), which has a characteristic green colour.
The reaction is often represented as: 2Cu(s) + H₂O(g) + CO₂(g) + O₂(g) → Cu₂(OH)₂CO₃(s) (basic copper carbonate). While the coating is technically a basic carbonate, “Copper carbonate” (referring to the presence of the carbonate group) is the closest option provided. Pure copper(II) carbonate (CuCO₃) is also green, but the patina is usually a mixture of CuCO₃ and Cu(OH)₂.

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