General Science – Physics MCQs
Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, UPSC, NDA, CDS and UPSC Civil Services Prelims Examinations.
31. Which of the following instruments is used to measure the relative density of a liquid?
[A] Hydrometer
[B] Hygrometer
[C] Lactometer
[D] Gravitimeter
Show Answer
Correct Answer: A [ Hydrometer ]
Notes:
A hydrometer is an instrument used to measure the specific gravity or relative density of liquids, i.e. the ratio of the density of the liquid to the density of water.
32. 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.
33. What is the Gaussian unit of kinematic viscosity?
[A] Henry
[B] Stokes
[C] poiseiulle
[D] Watt
Show Answer
Correct Answer: B [Stokes]
Notes:
The Gaussian unit of kinematic viscosity is stokes. Ten thousand stokes equal one square meter per second.
34. What is the S.I unit of frequency?
[A] Second
[B] Watt
[C] Hertz
[D] Joule
Show Answer
Correct Answer: C [Hertz]
Notes:
The frequency is defined as the number of periodic motions executed by body per second. The S.I unit of frequency is hertz (Hz).
35. What happens to the frequency of the pendulum if it is suspended from the ceiling of the lift moving up ward with constant acceleration?
[A] it decreases
[B] it increases
[C] may increase or decrease
[D] No change
Show Answer
Correct Answer: B [it increases]
Notes:
If the lift is moving up ward with constant acceleration a then the time period of the pendulum decreases and frequency increases.
36. What is the motion in which a body moves to and fro repeatedly about a fixed point in a definite interval of time known as?
[A] Circulatory Motion
[B] Rotary Motion
[C] Linear Motion
[D] Oscillatory Motion
Show Answer
Correct Answer: D [Oscillatory Motion]
Notes:
Oscillatory or vibratory motion is that motion in which a body moves to and fro or back and forth repeatedly about a fixed point in a definite interval of time. In such a motion, the body is confined with in well defined limits on either side of mean position.
37. Which of the following is correct about transverse mechanical waves?
[A] they can travel through solids and gases
[B] they can travel through solids but not liquids
[C] they can travel through solids and liquids
[D] they can travel through gases but not solids
Show Answer
Correct Answer: B [they can travel through solids but not liquids]
Notes:
In transverse waves, the constituents of the medium oscillate perpendicular to wave motion subjecting each element of the medium to shearing stress. Solids and strings have shear modulus, that is they sustain shearing stress. Fluids have no shape of their own – they yield to shearing stress. This is why transverse waves are possible in solids and strings (under tension) but not in fluids.
38. Which of the following waves is produced when inner shell electrons in atoms move from one energy level to a lower level?
[A] Infrared
[B] X-rays
[C] Ultraviolet
[D] Microwaves
Show Answer
Correct Answer: C [Ultraviolet]
Notes:
Ultraviolet rays are produced when the Inner shell electrons in atoms move from one energy level to a lower level.
39. Which of the following is correct about mechanical waves?
[A] they require a medium to propagate
[B] they don’t require a medium to propagate
[C] may or may not require a medium to propagate
[D] None of the above
Show Answer
Correct Answer: A [they require a medium to propagate]
Notes:
Mechanical waves require a medium for propagation as they cannot propagate through vacuum. Waves on a string, water waves, sound waves, seismic waves, etc. are the examples of mechanical waves.
40. What is the effect of increase of temperature on the speed of sound?
[A] it increases
[B] it decreases
[C] it may or may not increase
[D] No effect
Show Answer
Correct Answer: A [it increases]
Notes:
In any medium as we increase the temperature the speed of sound increases. For example, the speed of sound in air is 331 m s–1 at 0 ºC and 344 m s–1 at 22 ºC.
0 Comments