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. Why a small liquid drop is in spherical shape?
[A] due to surface tension
[B] due to low viscosity
[C] due to hydrogen bonding
[D] due to low density
Show Answer
Correct Answer: A [due to surface tension]
Notes:
For a given volume, the sphere has minimum surface area. A small liquid drop has spherical shape as due to surface tension the liquid surface tries to have minimum surface area.
32. Which is the effect of increase in impurities on the surface tension of the liquid?
[A] It increases
[B] It decreases
[C] It may increase or decrease
[D] No change
Show Answer
Correct Answer: C [It may increase or decrease]
Notes:
The presence of impurities considerably affect the force of surface tension, depending upon the degree of contamination. A highly soluble substance like sodium chloride when dissolved in water, increases the surface tension of water. But the sparingly soluble substances like phenol when dissolved in water, decreases the surface tension of water.
33. 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.
34. What is the phase of a vibrating particle at t = 0 known as?
[A] epoch
[B] eon
[C] path difference
[D] period
Show Answer
Correct Answer: A [epoch]
Notes:
Initial phase or epoch is the phase of a vibrating particle at t = 0. When t = 0; Phase is the angle of epoch.
35. By what phase angle the velocity is ahead of displacement in S.H.M?
[A] π
[B] π/4
[C] π/2
[D] 2π
Show Answer
Correct Answer: C [π/2]
Notes:
In S.H.M. the velocity is ahead of displacement by a phase angle π/ 2, the acceleration is ahead of velocity by a phase angle π/ 2 and the acceleration is ahead of displacement by a phase angle of π.
36. What do we call a motion which repeat itself over and over again after a regular interval of time?
[A] Periodic Motion
[B] Rotary Motion
[C] Linear Motion
[D] Rotational Motion
Show Answer
Correct Answer: A [Periodic Motion]
Notes:
A motion, which repeat itself over and over again after a regular interval of time is called a periodic motion and the fixed interval of time after which the motion is repeated is called period of the motion.
37. What kinds of waves are the ultrasonic waves in air produced by a vibrating quartz crystal?
[A] Transverse
[B] Longitudinal
[C] Transverse and longitudinal
[D] None of the above
Show Answer
Correct Answer: B [Longitudinal]
Notes:
The ultrasonic waves in air produced by a vibrating quartz crystal are longitudinal waves.
38. What is the wavelength range of Radio waves?
[A] between 400 nm and 800 nm
[B] between 1 nm and 10-3 nm
[C] more than 0.1 m
[D] None of the above
Show Answer
Correct Answer: C [more than 0.1 m]
Notes:
Radio waves are produced by the accelerated motion of charges in conducting wires. They are used in radio and television communication systems. They have frequencies from 300 GHz to as low as 3 kHz, and having wavelength range more than 0.1 m.
39. What is the relationship between the velocity of sound and the pressure of gas when the temperature remains constant?
[A] directly proportional to each other
[B] inversely proportional to each other
[C] independent of each other
[D] None of the above
Show Answer
Correct Answer: C [independent of each other]
Notes:
The velocity of sound is independent of the pressure of gas provided the temperature remains constant.
40. Which of the following is correct about a Sound wave?
[A] It is a mechanical wave
[B] It is an electromagnetic wave
[C] It is both a mechanical and electromagnetic wave
[D] It is neither a mechanical nor an electromagnetic wave
Show Answer
Correct Answer: A [It is a mechanical wave]
Notes:
Sound is a mechanical wave and cannot travel through a vacuum. It needs a medium to travel.
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