Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
11. Which of the following is true about displacement of an object?
[A] It is always equal to the distance travelled by the object
[B] It can be less than the distance travelled by the object
[C] It can be greater than the distance travelled by the object
[D] It always less than the distance travelled by the object
Show Answer
Correct Answer: B [It can be less than the distance travelled by the object]
Notes:
The displacement is the shortest distance between the initial and final position of an object in the given time. The displacement of an object is a vector quantity. It can be less than or equal to the distance but can never be greater than the distance travelled by that object
12. The time period of a satellite does not depend on which of the following?
[A] Radius of earth
[B] Height of the satellite
[C] Mass of the satellite
[D] None of the above
Show Answer
Correct Answer: C [Mass of the satellite]
Notes:
Time period of a satellite is the time taken by satellite to go once around the earth. The time period is independent of the mass of orbiting body and depends on the mass of central body and radius of the orbit.
13. What is the relation between the orbital velocity and the radius of the orbit for a given planet?
[A] greater the radius of orbit, lesser will be the orbital velocity
[B] greater the radius of orbit, greater will be the orbital velocity
[C] orbital velocity is independent of radius of orbit
[D] None of the above
Show Answer
Correct Answer: A [greater the radius of orbit, lesser will be the orbital velocity]
Notes:
For a given planet, greater the radius of orbit, lesser will be the orbital velocity of the satellite. The Orbital velocity depends on the mass of central body and radius of orbit.
14. Which of the following is NOT an example of capillary action?
[A] Rise of ink in the fine pores of blotting paper
[B] soaking of water by a towel
[C] Wood swells in rainy season due to rise of moisture
[D] None of the above
Show Answer
Correct Answer: D [None of the above]
Notes:
Examples of capillarity : (i) Ink rises in the fine pores of blotting paper leaving the paper dry. (ii) A towel soaks water. (iii) Oil rises in the long narrow spaces between the threads of a wick. (iv) Wood swells in rainy season due to rise of moisture from air in the pores.
15. What is Specific Gravity of a liquid?
[A] ratio of the density of a liquid to the density of water
[B] product of the density of a substance to the density of water
[C] ratio of the density of water to the density of a liquid
[D] ratio of density of the liquid to the mass of the equal density of water
Show Answer
Correct Answer: A [ ratio of the density of a liquid to the density of water ]
Notes:
Specific gravity of a liquid is the ratio of the density of a substance to the density of water. The density of liquid water at standard conditions on earth is approximately 1,000 kg/m3.
16. What is the density of water at 4°?
[A] 1.0
[B] 1.0 × 102 kg m–3
[C] 1.0 × 103 kg m–3
[D] 10 kg m–3
Show Answer
Correct Answer: C [ 1.0 × 103 kg m–3 ]
Notes:
The density of water at 4°C (277 K) is 1.0 × 103 kg m–3. The relative density of a substance is the ratio of its density to the density of water at 4° C.
17. What is the density of air at room temperature?
[A] 1.41
[B] 1.75
[C] 1.29
[D] 1.9
Show Answer
Correct Answer: C [ 1.29 ]
Notes:
The density of air at room temperature near the surface of the Earth is approximately 1.29 kg/m3.
18. What is Reynolds number?
[A] ratio of inertial force to viscous force
[B] ratio of weight of fluid to viscous force
[C] ratio of velocity gradient to viscous force
[D] reciprocal of viscous force
Show Answer
Correct Answer: A [ratio of inertial force to viscous force]
Notes:
Reynolds number is a dimensionless number, whose value gives one an approximate idea whether the flow would be turbulent. The Reynolds number (Re) is the ratio of inertial force (force due to inertia i.e., mass of moving fluid or due to inertia of obstacle in its path) to viscous force.
19. Which portion of the electromagnetic spectrum can be perceived by the human eye?
[A] Between 400 nm and 700 nm
[B] Between 40 nm and 70 nm
[C] Between 400 nm and 7000 nm
[D] Between 4 nm and 700 nm
Show Answer
Correct Answer: A [Between 400 nm and 700 nm]
Notes:
The human eye is capable of detecting light in the range of approximately 400 nm to 700 nm on the electromagnetic spectrum. This corresponds to the frequency range of about 4 × 10^14 to 7 × 10^14 Hz. This detection range falls within the visible light spectrum. It’s fascinating how our eyes are naturally tuned to this specific range, enabling us to perceive the palette of colors in our surroundings but unable to see ultraviolet or infrared radiation that are just outside this narrow band.
20. Which of the following conditions will not show any Doppler effect?
[A] When source and listener both are at rest
[B] When medium alone is moving
[C] When source and listener are moving in mutually perpendicular directions
[D] All of the above
Show Answer
Correct Answer: D [All of the above]
Notes:
Conditions for no Doppler effect : (i) When source (S) and listener (L) both are at rest. (ii) When medium alone is moving. (iii) When S and L move in such a way that distance between S and L remains constant. (iv) When source S and listener L, are moving in mutually perpendicular directions
