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CSS MCQs

Civil Superior Services — Complete MCQ Bank

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121
Physics Medium

What is the principle of conservation of momentum?

  • AMomentum increases with velocity only
  • BTotal momentum of an isolated system remains constant
  • CMomentum equals mass times acceleration
  • DMomentum decreases with time
Permalink
Correct Answer: Option B — Total momentum of an isolated system remains constant
Explanation: The principle of conservation of momentum states that the total momentum of an isolated system remains constant provided no external forces act on it.
Submitted by: PaperMCQs
122
Physics Medium

Which principle explains why an aircraft wing generates lift?

  • APascal's principle
  • BBernoulli's principle
  • CArchimedes' principle
  • DNewton's first law only
Permalink
Correct Answer: Option B — Bernoulli's principle
Explanation: Bernoulli's principle explains that faster moving air over the curved upper wing surface has lower pressure than the slower air beneath creating a net upward lift force.
Submitted by: PaperMCQs
123
Physics Medium

Which formula correctly represents the relationship between frequency wavelength and speed of a wave?

  • Av equals f divided by wavelength
  • Bv equals wavelength divided by f
  • Cv equals f times wavelength
  • Df equals v times wavelength
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Correct Answer: Option C — v equals f times wavelength
Explanation: The wave equation states that wave speed v equals frequency f multiplied by wavelength lambda showing that for a given medium as frequency increases wavelength decreases proportionally.
Submitted by: PaperMCQs
124
Physics Hard

What is the critical angle in optics?

  • AAngle at which light travels along the boundary between two media
  • BAngle at which refraction stops
  • CAngle at which a lens focuses parallel rays
  • DAngle of maximum diffraction
Permalink
Correct Answer: Option A — Angle at which light travels along the boundary between two media
Explanation: The critical angle is the angle of incidence in the denser medium at which the refracted ray travels along the boundary and above which total internal reflection occurs.
Submitted by: PaperMCQs
125
Physics Medium

What is the half-life of a radioactive substance?

  • ATime for the substance to completely decay
  • BTime for the radiation to halve in intensity only
  • CTime for half the nuclei to decay
  • DTime for temperature to reduce by half
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Correct Answer: Option C — Time for half the nuclei to decay
Explanation: Half-life is the time required for half of the radioactive nuclei in a sample to decay and it is a constant characteristic value specific to each radioactive isotope.
Submitted by: PaperMCQs
126
Physics Medium

Which type of radiation consists of helium nuclei emitted from an unstable nucleus?

  • AAlpha radiation
  • BBeta radiation
  • CGamma radiation
  • DNeutron radiation
Permalink
Correct Answer: Option A — Alpha radiation
Explanation: Alpha radiation consists of particles identical to helium-4 nuclei containing two protons and two neutrons emitted from heavy unstable nuclei during radioactive decay.
Submitted by: PaperMCQs
127
Physics Medium

Which type of radiation has the highest penetrating power?

  • AAlpha radiation
  • BGamma radiation
  • CBeta radiation
  • DNeutron radiation
Permalink
Correct Answer: Option B — Gamma radiation
Explanation: Gamma radiation is highly penetrating electromagnetic radiation that can pass through most materials and requires dense materials like thick lead or concrete for adequate shielding.
Submitted by: PaperMCQs
128
Physics Medium

What is the Doppler effect in the context of sound waves?

  • AChange in speed of sound due to medium
  • BChange in amplitude of sound near a source
  • CEcho formation from hard surfaces
  • DApparent change in frequency due to relative motion between source and observer
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Correct Answer: Option D — Apparent change in frequency due to relative motion between source and observer
Explanation: The Doppler effect describes the apparent change in frequency of sound or light when the source and observer are in relative motion with frequency increasing as they approach and decreasing as they move apart.
Submitted by: PaperMCQs
129
Physics Medium

Which experiment proved that the atom has a small dense positively charged nucleus?

  • ARutherford's gold foil experiment
  • BMillikan's oil drop experiment
  • CYoung's double slit experiment
  • DMichelson-Morley experiment
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Correct Answer: Option A — Rutherford's gold foil experiment
Explanation: Rutherford's gold foil experiment in 1909 proved that atoms have a small dense positively charged nucleus surrounded by mostly empty space through which alpha particles passed.
Submitted by: PaperMCQs
130
Physics Medium

Which model of the atom describes electrons orbiting the nucleus in specific energy levels?

  • AThomson's Plum Pudding model
  • BRutherford's model
  • CDalton's model
  • DBohr's atomic model
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Correct Answer: Option D — Bohr's atomic model
Explanation: Bohr's atomic model proposed in 1913 describes electrons orbiting the nucleus in fixed energy levels or shells and electrons emit or absorb energy when transitioning between levels.
Submitted by: PaperMCQs
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