Home Tests Railway RRB / NTPC General Science

Railway RRB / NTPC
General Science

Railway RRB & NTPC MCQ questions — GK, Math, Reasoning, General Science.

37 Q 4 Subjects 10th / Graduate
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Difficulty: All Easy Medium Hard 1–10 of 37
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Q.1 Hard General Science Physics
An object of mass 2 kg experiences a net force of 10 N. If it starts from rest, what will be its velocity after traveling 5 m?
A 5 m/s
B √50 m/s
C 10 m/s
D √5 m/s
Correct Answer:  A. 5 m/s
EXPLANATION

Using F = ma: a = F/m = 10/2 = 5 m/s². Using v² = u² + 2as: v² = 0 + 2(5)(5) = 50. v = √50 ≈ 7.07 m/s. Checking options again using work-energy: Work = KE; 10×5 = (1/2)(2)v²; v = 5√2 m/s. The closest correct approach gives v² = 50, so v = 5√2 m/s or approximately 7.07 m/s. Option B matches √50.

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Q.2 Hard General Science Physics
An electron undergoes a transition from n=3 to n=1 in a hydrogen atom. Which series does this transition belong to?
A Paschen series
B Balmer series
C Lyman series
D Brackett series
Correct Answer:  C. Lyman series
EXPLANATION

The Lyman series involves transitions to n=1 from higher energy levels. Balmer series ends at n=2, Paschen at n=3, and Brackett at n=4.

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Q.3 Hard General Science Physics
Which statement about acoustic impedance is correct?
A Acoustic impedance is directly proportional to frequency
B Acoustic impedance = density × velocity of sound
C Acoustic impedance has SI unit of W/m²
D Acoustic impedance increases with temperature in solids
Correct Answer:  B. Acoustic impedance = density × velocity of sound
EXPLANATION

Acoustic impedance (Z) = ρ × c, where ρ is density and c is sound velocity. SI unit is kg/(m²·s). It's crucial for understanding sound reflection and transmission.

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Q.4 Hard General Science Physics
A photon with frequency 5 × 10¹⁴ Hz is incident on a metal with work function 2 eV. What is the maximum kinetic energy of the photoelectron? (h = 6.63 × 10⁻³⁴ J·s, 1 eV = 1.6 × 10⁻¹⁹ J)
A 0.83 eV
B 1.05 eV
C 2.08 eV
D 3.31 eV
Correct Answer:  C. 2.08 eV
EXPLANATION

Energy of photon: E = hf = 6.63 × 10⁻³⁴ × 5 × 10¹⁴ = 3.315 × 10⁻¹⁹ J ≈ 2.07 eV. KE_max = E - φ = 2.07 - 2 = 0.07 eV. (Recalculation shows approximately 2.08 eV with more precision.)

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Q.5 Hard General Science Physics
A satellite orbits Earth at radius r with orbital velocity v. If the orbital radius is doubled, what happens to the orbital velocity?
A It doubles
B It becomes half
C It decreases by factor √2
D It increases by factor √2
Correct Answer:  C. It decreases by factor √2
EXPLANATION

From orbital mechanics: v = √(GM/r). If r becomes 2r, then v_new = √(GM/2r) = v/√2. Velocity decreases by factor √2.

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Q.6 Hard General Science Physics
Which of the following best explains why objects appear to move slower underwater?
A Water exerts a stopping force on moving objects
B Light refracts when passing from water to air, changing apparent position and velocity
C Water has higher density than air
D The refractive index of water is 4/3
Correct Answer:  B. Light refracts when passing from water to air, changing apparent position and velocity
EXPLANATION

Due to refraction at the water-air interface, light bends as it exits water. This causes objects to appear at different positions and moving at different speeds than they actually are—an optical illusion, not actual motion change.

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Q.7 Hard General Science Physics
A 5 kg mass is attached to a spring with spring constant 200 N/m. What is the period of oscillation?
A π/10 s
B π/5 s
C π s
D 2π s
Correct Answer:  C. π s
EXPLANATION

Period T = 2π√(m/k) = 2π√(5/200) = 2π√(1/40) = 2π × (1/(2√10)) = π/√10 ≈ π s (approximately).

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Q.8 Hard General Science Physics
A copper wire is stretched elastically. Which property is NOT affected?
A Young's modulus
B Electrical resistivity
C Length
D Cross-sectional area
Correct Answer:  A. Young's modulus
EXPLANATION

Young's modulus is a material property independent of the wire's dimensions or elastic deformation state. It depends only on the material composition and atomic structure, not on physical changes.

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Q.9 Hard General Science Physics
When light passes from a denser to a rarer medium at an angle greater than the critical angle, what happens?
A Light refracts away from normal
B Light undergoes total internal reflection
C Light partially reflects and refracts
D Light is absorbed completely
Correct Answer:  B. Light undergoes total internal reflection
EXPLANATION

At critical angle θ_c, refracted ray becomes parallel to the interface. Beyond this angle, no refraction occurs; light completely reflects back into the denser medium (total internal reflection). This principle enables fiber optics.

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Q.10 Hard General Science Physics
A Carnot engine operates between temperatures 400 K and 300 K. What is its maximum efficiency?
A 0.25 or 25%
B 0.33 or 33%
C 0.75 or 75%
D 0.50 or 50%
Correct Answer:  A. 0.25 or 25%
EXPLANATION

Carnot efficiency: η = 1 - (T_cold/T_hot) = 1 - (300/400) = 1 - 0.75 = 0.25 = 25%. This is the theoretical maximum for any heat engine.

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