UPSC NDA-1 Archives

31. Cell wall of any fungus is different from plants in having

Cell wall of any fungus is different from plants in having

[amp_mcq option1=”cellulose” option2=”chitin” option3=”cholesterol” option4=”glycogen” correct=”option2″]

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UPSC NDA-1 – 2017

Plant cell walls are primarily composed of cellulose, a polysaccharide. The cell walls of fungi, however, are primarily composed of chitin, a nitrogen-containing polysaccharide also found in the exoskeletons of insects and crustaceans. This difference in cell wall composition is a key characteristic distinguishing fungi from plants.

Fungal cell walls contain chitin, whereas plant cell walls contain cellulose.

The presence of chitin in fungal cell walls is targeted by some antifungal drugs, making it an important difference from human cells which lack cell walls. Glycogen is a common storage carbohydrate in both fungi and animals, not a cell wall component. Cholesterol is a lipid found in animal cell membranes, not plant or fungal cell walls.

32. Glass is a

Glass is a

[amp_mcq option1=”liquid” option2=”colloid” option3=”non-crystalline amorphous solid” option4=”crystalline solid” correct=”option3″]

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Glass is a non-crystalline amorphous solid. Unlike crystalline solids which have a highly ordered, repeating atomic structure, glass has a disordered atomic structure similar to a liquid, but it is rigid and retains its shape like a solid over geological timescales. It is sometimes described as a supercooled liquid because it flows extremely slowly, although this is a simplified view; a more accurate description is that it exists in a glass state, which is a rigid, disordered state.

Glass lacks the long-range crystalline order found in crystalline solids and is considered an amorphous solid.

Common glass (soda-lime glass) is primarily composed of silicon dioxide (silica, SiO2), with additives like sodium carbonate (soda ash) and calcium carbonate (lime) to lower its melting point and improve workability.

33. Rutherford’s alpha-particle scattering experiment was responsible for

Rutherford’s alpha-particle scattering experiment was responsible for the discovery of

[amp_mcq option1=”Electron” option2=”Proton” option3=”Nucleus” option4=”Helium” correct=”option3″]

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Rutherford’s alpha-particle scattering experiment, also known as the gold foil experiment, involved firing alpha particles (positively charged helium nuclei) at a thin gold foil. The observation that most particles passed through, some were deflected, and a few were scattered back at large angles led Rutherford to propose that atoms have a very small, dense, positively charged center, which he named the nucleus.

Rutherford’s alpha-scattering experiment established the existence of the atomic nucleus.

While the experiment provided evidence for a positive charge in the nucleus (later identified as protons), it was the discovery of the nucleus itself as the dense core of the atom that was the direct result of analyzing the scattering patterns. Electrons were discovered earlier by J.J. Thomson. Neutrons were discovered later by James Chadwick.

34. Which one of the following elements is least reactive with water ?

Which one of the following elements is least reactive with water ?

[amp_mcq option1=”Lithium” option2=”Sodium” option3=”Potassium” option4=”Cesium” correct=”option1″]

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Lithium, Sodium, Potassium, and Cesium are alkali metals belonging to Group 1 of the periodic table. The reactivity of alkali metals with water increases down the group due to the decreasing ionization energy and increasing atomic size, making it easier to lose the valence electron. Therefore, Lithium (Li) is the least reactive with water among the given options, while Cesium (Cs) is the most reactive.

Reactivity of alkali metals with water increases from Lithium to Cesium.

Lithium reacts slowly with water, producing hydrogen gas and lithium hydroxide. Sodium reacts vigorously, often melting due to the heat produced. Potassium, Rubidium, and Cesium react increasingly explosively with water.

35. Stung by hairs of nettle leaves causes burning pain. This is due to th

Stung by hairs of nettle leaves causes burning pain. This is due to the injection of

[amp_mcq option1=”Acetic acid” option2=”Methanoic acid” option3=”Sulphuric acid” option4=”Hydrochloric acid” correct=”option2″]

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The burning pain caused by stinging hairs of nettle leaves is primarily due to the injection of chemicals including formic acid, also known by its systematic name methanoic acid (HCOOH). Other irritants like histamine, acetylcholine, and serotonin are also present, but methanoic acid is a key contributor to the stinging sensation.

Methanoic acid (formic acid) is responsible for the stinging pain from nettle hairs.

Applying a weak base, such as a solution of baking soda or rubbing the affected area with the leaves of docks (often found growing near nettles), can help neutralize the acid and relieve the pain.

36. Temporary hardness in water is due to which one of the following of Ca

Temporary hardness in water is due to which one of the following of Calcium and Magnesium ?

[amp_mcq option1=”Hydrogen carbonates” option2=”Carbonates” option3=”Chlorides” option4=”Sulphates” correct=”option1″]

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Temporary hardness in water is caused by the presence of dissolved bicarbonates (also known as hydrogen carbonates) of calcium and magnesium, such as Ca(HCO3)2 and Mg(HCO3)2. These can precipitate out as insoluble carbonates when the water is boiled, thereby removing the hardness.

Temporary hardness is due to soluble bicarbonates of calcium and magnesium and can be removed by boiling.

Permanent hardness is caused by dissolved chlorides and sulphates of calcium and magnesium (e.g., CaCl2, MgCl2, CaSO4, MgSO4) and cannot be removed by boiling. Water softening methods are required to remove permanent hardness.

37. Molecules of which of the following has cage like structure ? 1. Dia

Molecules of which of the following has cage like structure ?

1. Diamond

2. Graphite

3. Fullerenes

Select the correct answer using the code given below :

[amp_mcq option1=”1, 2 and 3″ option2=”2 and 3 only” option3=”2 only” option4=”3 only” correct=”option4″]

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Fullerenes are allotropes of carbon characterized by their spherical or cage-like structures. The most well-known fullerene is C60, which has a structure resembling a soccer ball. Diamond has a rigid, three-dimensional tetrahedral network structure. Graphite consists of layers of hexagonal carbon rings. Neither diamond nor graphite have discrete, cage-like molecules.

Fullerenes are molecular allotropes of carbon with characteristic closed cage structures.

Fullerenes were discovered in 1985 by Robert Curl, Harold Kroto, and Richard Smalley, who were awarded the Nobel Prize in Chemistry in 1996 for their discovery. They have potential applications in materials science, electronics, and medicine.

38. The speed of a body that has Mach number more than 1 is

The speed of a body that has Mach number more than 1 is

[amp_mcq option1=”supersonic” option2=”subsonic” option3=”300 m/s” option4=”about 10 m/s” correct=”option1″]

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Mach number is defined as the ratio of the speed of an object in a medium to the speed of sound in that medium.
– Mach number = 1: Speed of the object equals the speed of sound (sonic).
– Mach number < 1: Speed of the object is less than the speed of sound (subsonic). - Mach number > 1: Speed of the object is greater than the speed of sound (supersonic).
– Mach number > 5: Speed of the object is much greater than the speed of sound (hypersonic).
The question asks for the speed of a body that has a Mach number more than 1, which corresponds to supersonic speed.

– Mach number is a dimensionless quantity representing the ratio of speed to the speed of sound.
– Mach > 1 means supersonic speed.
– Mach < 1 means subsonic speed. - Mach = 1 means sonic speed.

The speed of sound varies depending on the medium (e.g., air, water) and its properties (e.g., temperature, pressure). In dry air at 15°C at sea level, the speed of sound is approximately 340 m/s (around 1225 km/h or 761 mph). So, a speed of 300 m/s (Option C) is close to Mach 1 but not necessarily supersonic, and the statement about 10 m/s (Option D) is clearly subsonic.

39. The speed of a car travelling on a straight road is listed below at su

The speed of a car travelling on a straight road is listed below at successive intervals of 1 s :

Time (s) | 0 | 1 | 2 | 3 | 4
——- | – | – | – | – | –
Speed (m/s) | 0 | 2 | 4 | 6 | 8

Which of the following is/are correct? The car travels

1. with a uniform acceleration of 2 m/s².
2. 16 m in 4 s.
3. with an average speed of 4 m/s.

Select the correct answer using the code given below :

[amp_mcq option1=”1, 2 and 3″ option2=”2 and 3 only” option3=”1 and 2 only” option4=”1 only” correct=”option1″]

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Let’s analyze each statement based on the given speed data:
1. with a uniform acceleration of 2 m/s²: The speed increases by 2 m/s every second (0 to 2, 2 to 4, 4 to 6, 6 to 8). Acceleration = change in speed / change in time = 2 m/s / 1 s = 2 m/s². Since this value is constant, the acceleration is uniform. Statement 1 is correct.
2. 16 m in 4 s: Assuming the car starts from rest (speed = 0 at time = 0) and moves with uniform acceleration (a = 2 m/s²), the distance covered in time t is given by s = ut + (1/2)at², where u is the initial speed (0 m/s). For t = 4s, s = (0)(4) + (1/2)(2)(4)² = 0 + 1 * 16 = 16 m. Statement 2 is correct.
3. with an average speed of 4 m/s: Average speed is total distance / total time. Total distance covered is 16 m (from statement 2) and total time is 4 s. Average speed = 16 m / 4 s = 4 m/s. Statement 3 is correct.
All three statements are correct.

– Uniform acceleration means the velocity changes by the same amount in equal intervals of time.
– For uniformly accelerated motion, cinematic equations can be used to calculate distance, speed, and time.
– Average speed is calculated as total distance traveled divided by the total time taken.

In uniformly accelerated motion starting from rest, the speed at time t is v = at, and the distance covered is s = (1/2)at². The average speed over a time interval is (initial speed + final speed) / 2 if acceleration is uniform. In this case, average speed over 4s is (0 + 8)/2 = 4 m/s, confirming statement 3.

40. At which place Earth’s magnetic field becomes horizontal ?

At which place Earth’s magnetic field becomes horizontal ?

[amp_mcq option1=”Magnetic meridian” option2=”Magnetic equator” option3=”Geographical pole” option4=”Tropic of Cancer” correct=”option2″]

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The Earth’s magnetic field lines are not uniform. The magnetic dip angle (or angle of inclination) is the angle that the Earth’s magnetic field makes with the horizontal plane at a given location. At the Magnetic Equator, the magnetic field lines are parallel to the Earth’s surface, meaning the magnetic dip angle is 0 degrees. Therefore, the Earth’s magnetic field is horizontal at the Magnetic Equator. At the magnetic poles, the field lines are vertical, and the dip angle is 90 degrees.

– The magnetic dip angle is the angle between the Earth’s magnetic field and the horizontal.
– The magnetic dip angle is 0 degrees at the Magnetic Equator.
– The magnetic dip angle is 90 degrees at the Magnetic Poles.

The Magnetic Equator is an imaginary line around the Earth where a freely dipping magnetic needle remains horizontal. It is not the same as the geographical equator, and its position varies slowly over time due to the shifting of the Earth’s magnetic field. The magnetic meridian at a point is the vertical plane passing through the magnetic axis at that point.