UPSC CAPF Archives

41. Which one of the following statements about alkaline earth metals is N

Which one of the following statements about alkaline earth metals is NOT true ?

[amp_mcq option1=”Strontium salts burn with a red flame” option2=”Barium metal is used in medicine to examine the alimentary canal of a patient by X-ray” option3=”Green plants need magnesium in order to make the chlorophyll that trap the energy from sunlight in photosynthesis” option4=”Red colour of gemstone Ruby is due to the element beryllium present in it” correct=”option2″]

This question was previously asked in

UPSC CAPF – 2020

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The statement “Barium metal is used in medicine to examine the alimentary canal of a patient by X-ray” is NOT true.

For X-ray examination of the alimentary canal (Barium meal), a suspension of Barium *sulfate* (BaSO4) is used as a contrast medium. Barium sulfate is very insoluble and thus passes through the digestive system safely. Barium *metal* is highly reactive and toxic, and would react with water or acids in the body, making it unsuitable and dangerous for internal consumption or medical use in this manner.

A) Strontium salts (e.g., SrCl2) do burn with a red flame, used in fireworks. C) Magnesium is a crucial component of chlorophyll, essential for photosynthesis in green plants. D) The red colour of ruby is due to the presence of chromium ions (Cr3+) substituted into the aluminum oxide (Al2O3) lattice; beryllium is a component of other gemstones like emerald (which is beryl, a beryllium aluminum silicate, colored by chromium or vanadium). Statements A, C, and D are all factual statements (or factually correct denials, in the case of D’s claim about beryllium). Statement B is factually incorrect regarding the *form* of Barium used in medicine.

42. Which one of the following ingredients does NOT constitute paint ?

Which one of the following ingredients does NOT constitute paint ?

[amp_mcq option1=”Turpentine oil (thinner)” option2=”Poly-hydroxy phenols (anti-skinning agent)” option3=”Thiourea (accelerator)” option4=”Titanium dioxide (pigment)” correct=”option3″]

This question was previously asked in

UPSC CAPF – 2020

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Thiourea is NOT a standard ingredient that constitutes paint.

Typical paint formulations include Pigments (like Titanium dioxide for white color), Binders (resins or polymers that form a film), Solvents or Thinners (like turpentine oil or water to adjust viscosity), and various Additives (such as driers, anti-skinning agents like poly-hydroxy phenols, dispersants, etc.). Thiourea is an organic compound with various uses, including in resins, fertilizers, and as a vulcanization accelerator in rubber, but it is not a common or standard component of paint.

Turpentine oil is a common solvent/thinner. Poly-hydroxy phenols are used as anti-skinning agents. Titanium dioxide is a widely used white pigment. These are all standard ingredients or types of ingredients found in paints.

43. Magnesium is used in

Magnesium is used in

[amp_mcq option1=”fireworks to make a bright white light” option2=”gemstones in jewellery” option3=”examination of alimentary canal of the patient” option4=”purification of water” correct=”option1″]

This question was previously asked in

UPSC CAPF – 2020

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Magnesium is used in fireworks to make a bright white light.

Magnesium metal burns rapidly in air with a brilliant white flame, producing magnesium oxide (MgO). This property makes it useful in fireworks, flares, and incendiary devices to create intense light.

B) Gemstones in jewellery are typically minerals like corundum (ruby, sapphire), diamond, beryl, etc., which do not primarily contain magnesium as a main component providing aesthetic value in this context. C) Examination of the alimentary canal often uses Barium sulfate (BaSO4) as a contrast medium in X-rays, not magnesium. D) While magnesium compounds can be involved in water treatment (e.g., precipitating impurities), magnesium metal itself is not typically used directly for purification of water.

44. Which one of the following statements with regard to Newton’s third la

Which one of the following statements with regard to Newton’s third law of motion is NOT correct?

[amp_mcq option1=”Force never occurs singly in nature” option2=”When the earth pulls a stone downwards due to gravity, the stone exerts a force on the earth” option3=”There is ‘a cause-effect relation implied in the third law” option4=”There is no cause-effect relation implied in the third law” correct=”option3″]

This question was previously asked in

UPSC CAPF – 2020

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The statement “There is ‘a cause-effect relation implied in the third law” is NOT correct with regard to Newton’s third law of motion.

Newton’s third law states that for every action, there is an equal and opposite reaction. These action and reaction forces are a pair and occur simultaneously as part of a single interaction between two bodies. The law describes the nature of forces as interactions rather than implying one force causes the other in a sequential manner. There is no temporal delay or causal dependency between the action and reaction forces; they exist concurrently. Statement D, “There is no cause-effect relation implied in the third law”, is consistent with this understanding.

Statements A and B correctly describe aspects of the third law. A) Force never occurs singly in nature implies forces always come in pairs (action-reaction pairs). B) When the earth pulls a stone downwards due to gravity, the stone exerts a force on the earth is the classic example of an action-reaction pair according to the third law.

45. The radar used by police to check over-speeding vehicles works on the

The radar used by police to check over-speeding vehicles works on the principle of

[amp_mcq option1=”Raman effect” option2=”Induction effect” option3=”Doppler effect” option4=”Coulomb effect” correct=”option3″]

This question was previously asked in

UPSC CAPF – 2020

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The radar used by police to check over-speeding vehicles works on the principle of the Doppler effect.

The Doppler effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. Police radar guns emit radio waves towards a moving vehicle. When these waves reflect off the vehicle, their frequency is shifted. If the vehicle is moving towards the radar, the reflected waves have a higher frequency; if moving away, they have a lower frequency. The radar unit measures this frequency shift and calculates the vehicle’s speed based on the magnitude of the shift.

The Raman effect involves inelastic scattering of photons. The Induction effect relates to the production of an electromotive force across an electrical conductor in a changing magnetic field. The Coulomb effect describes the electrostatic interaction between charged particles. None of these principles are the basis for how police speed radar operates.

46. Which one of the following statements regarding motion is correct?

Which one of the following statements regarding motion is correct?

[amp_mcq option1=”All the periodic motions are necessarily simple harmonic” option2=”All the simple harmonic motions are necessarily periodic motions” option3=”There is no co-relation between the simple harmonic motions and the periodicity of motion” option4=”The relation between the simple harmonic motion and periodic motion depends upon the mass of object undergoing the motion” correct=”option2″]

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UPSC CAPF – 2020

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All the simple harmonic motions are necessarily periodic motions.

Periodic motion is defined as any motion that repeats itself in a regular interval of time. Simple Harmonic Motion (SHM) is a special type of periodic motion where the restoring force is directly proportional to the displacement from the equilibrium position and acts towards the equilibrium. Since SHM repeats itself at regular intervals (its period), it is always a periodic motion. However, not all periodic motions are SHM (e.g., a simple pendulum with large amplitude is periodic but not SHM; a uniform circular motion is periodic but not oscillatory/SHM).

SHM is characterized by a sinusoidal variation of displacement, velocity, and acceleration with time. Examples include the oscillation of a mass on a spring (Hooke’s Law) or the small-angle oscillations of a simple pendulum.

47. Which one of the following statements regarding Fleming’s Rule is co

Which one of the following statements regarding Fleming’s Rule is correct?

[amp_mcq option1=”Fleming’s left hand rule gives direction of force on a current-carrying conductor in a magnetic field” option2=”Fleming’s right hand rule gives direction of force on a current-carrying conductor in a magnetic field” option3=”Both the left-hand and right-hand rule can be used for finding direction of force on a current-carrying conductor in a magnetic field” option4=”Fleming’s rules has nothing to do with magnetic field” correct=”option1″]

This question was previously asked in

UPSC CAPF – 2020

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Fleming’s left hand rule gives direction of force on a current-carrying conductor in a magnetic field.

Fleming’s Left-Hand Rule is used to determine the direction of the force (thrust or motion) on a current-carrying conductor when placed in an external magnetic field. It relates the directions of the magnetic field, the electric current, and the resulting force. The thumb represents the direction of the force, the forefinger represents the direction of the magnetic field, and the middle finger represents the direction of the current.

Fleming’s Right-Hand Rule is used to determine the direction of induced current when a conductor moves in a magnetic field. It is used in generators. The Left-Hand Rule is primarily used in motors.

48. Two magnetic field lines produced by the same source

Two magnetic field lines produced by the same source

[amp_mcq option1=”never intersect” option2=”can originate from same point” option3=”can terminate at same point” option4=”can intersect depending on situation” correct=”option1″]

This question was previously asked in

UPSC CAPF – 2020

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Two magnetic field lines produced by the same source never intersect.

Magnetic field lines represent the direction of the magnetic field at different points. If two magnetic field lines were to intersect at a point, it would mean that the magnetic field at that point has two different directions simultaneously, which is impossible.

Magnetic field lines are continuous curves forming closed loops (outside the magnet from North to South, inside from South to North). They are denser where the magnetic field is stronger. They originate from the North pole and terminate at the South pole outside the magnet.

49. Which one of the following statements for an object falling freely und

Which one of the following statements for an object falling freely under the influence of gravity is correct?

[amp_mcq option1=”Zero acceleration always implies zero velocity” option2=”Zero acceleration has no relation with the velocity of the object” option3=”Zero velocity at any instant necessarily means zero acceleration at that instant” option4=”Acceleration is constant all throughout the free fall” correct=”option4″]

This question was previously asked in

UPSC CAPF – 2020

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Acceleration is constant all throughout the free fall.

An object falling freely under the influence of gravity experiences a constant acceleration equal to the acceleration due to gravity (g), assuming air resistance is negligible. This acceleration acts downwards.

Zero acceleration implies constant velocity, not necessarily zero velocity (A is incorrect). Zero acceleration means there is no net force acting on the object; velocity could be constant and non-zero (B is incorrect). An object thrown upwards momentarily has zero velocity at its peak, but the acceleration due to gravity is still acting on it at that instant (C is incorrect).

50. Which one among the following was the first country to declare ‘Climat

Which one among the following was the first country to declare ‘Climate Emergency’ ?

[amp_mcq option1=”Sweden” option2=”New Zealand” option3=”UK” option4=”Ireland” correct=”option3″]

This question was previously asked in

UPSC CAPF – 2019

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The UK Parliament was the first legislative body in the world to declare a ‘climate emergency’.

On May 1, 2019, the UK Parliament passed a motion declaring a “climate emergency,” becoming the first country’s legislature to do so. This followed lobbying by environmental groups like Extinction Rebellion.

Declaring a climate emergency is a call to governments to acknowledge the urgency of the climate crisis and take action to address it rapidly. Many other countries, sub-national entities, and cities have since declared climate emergencies.