Science MCQs (Physics):
Physics MCQs – Set 20
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Science MCQs (Physics) – Set 20
Level: FINAL ULTRA-EXTREME + Numerical + Conceptual Traps
Highly useful for SSC CGL, Railway JE, NDA, HP SET, State PCS
Physics MCQs – Set 20 (20 Questions with Explanation)
1. A body moves with constant velocity. Which of the following is true?
A. Net force is zero
B. Acceleration is maximum
C. Momentum is zero
D. Kinetic energy is zero
✅ Answer: A
📘 Explanation: Constant velocity ⇒ zero acceleration ⇒ net force = 0.
2. The dimensional formula of gravitational constant (G) is:
A. [M⁻¹L³T⁻²]
B. [ML³T⁻²]
C. [M⁻²L³T⁻²]
D. [ML²T⁻¹]
✅ Answer: A
📘 Explanation: From F = Gm₁m₂/r².
3. A body of mass 1 kg moving with speed 4 m/s collides elastically with a wall. Change in momentum is:
A. 0
B. 4 kg·m/s
C. 8 kg·m/s
D. 16 kg·m/s
✅ Answer: C
📘 Explanation: Momentum reverses ⇒ Δp = 2mv = 8 kg·m/s.
4. If the length of a wire is tripled and its radius doubled, the new resistance is:
A. 3R
B. ¾ R
C. 12R
D. 3/4 R
✅ Answer: B
📘 Explanation:
R ∝ L/r² ⇒ (3)/(2²) = 3/4 R.
5. The work done by a centripetal force is always:
A. Maximum
B. Positive
C. Negative
D. Zero
✅ Answer: D
📘 Explanation: Force ⟂ displacement.
6. Assertion (A): Escape velocity of Earth is independent of the mass of the body.
Reason (R): Escape velocity depends on Earth's mass and radius.
A. Both true, R correct explanation
B. Both true, R not explanation
C. A true, R false
D. A false, R true
✅ Answer: A
7. The SI unit of magnetic flux density is:
A. Weber
B. Tesla
C. Henry
D. Ampere
✅ Answer: B
8. The image formed by a convex mirror is always:
A. Real and inverted
B. Virtual and erect
C. Real and erect
D. Virtual and inverted
✅ Answer: B
9. The phenomenon used in optical fibre communication is:
A. Refraction
B. Dispersion
C. Diffraction
D. Total internal reflection
✅ Answer: D
10. The pitch of a sound increases when:
A. Amplitude increases
B. Frequency increases
C. Velocity increases
D. Wavelength increases
✅ Answer: B
11. A transformer works on the principle of:
A. Self induction
B. Mutual induction
C. Electrostatics
D. Heating effect
✅ Answer: B
12. The SI unit of electric power is:
A. Joule
B. Volt
C. Ampere
D. Watt
✅ Answer: D
13. Which electromagnetic wave has the highest frequency?
A. X-rays
B. Ultraviolet
C. Gamma rays
D. Infrared
✅ Answer: C
14. Assertion (A): Sound waves cannot travel in vacuum.
Reason (R): Sound waves are mechanical waves.
A. Both true, R correct explanation
B. Both true, R not explanation
C. A true, R false
D. A false, R true
✅ Answer: A
15. The efficiency of a Carnot engine depends on:
A. Nature of gas
B. Volume of gas
C. Pressure of gas
D. Temperatures of source and sink
✅ Answer: D
16. The phenomenon responsible for mirage is:
A. Reflection
B. Refraction
C. Diffraction
D. Total internal reflection
✅ Answer: D
17. The time period of a simple pendulum depends on:
A. Mass of bob
B. Length of string
C. Material of bob
D. Shape of bob
✅ Answer: B
18. Which effect confirms the particle nature of light?
A. Interference
B. Diffraction
C. Polarization
D. Photoelectric effect
✅ Answer: D
19. The unit of electric potential is:
A. Joule
B. Coulomb
C. Volt
D. Ampere
✅ Answer: C
20. Which quantity has the same unit as torque?
A. Power
B. Energy
C. Momentum
D. Force
✅ Answer: B
📘 Explanation: Torque and energy both have unit N·m (nature different).
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