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.
21. An earth satellite S has an orbit radius which is 2 times that of a communication satellite C. What will be the period of revolution of S?
[A] 1 day
[B] 2 days
[C] 4 days
[D] 8 days
Show Answer
Correct Answer: C [4 days]
Notes:
As per Kepler’s third law, the square of the period of any planet is proportional to the cube of the semimajor axis of its orbit. Ts/Tc = 23/2= 4 days
22. What is the upward force experienced by a body, when it is immersed in a fluid, known as?
[A] Tangential force
[B] Buoyant force
[C] Centrifugal force
[D] Hydraulic force
Show Answer
Correct Answer: B [Buoyant force]
Notes:
When a body is immersed in a fluid (liquid or gas) it exerts an upward force on that body. This upward force is called up thrust or buoyant force, The whole phenomenon is called as buoyancy.
23. Which of the following represents the Density of a material?
[A] Mass/weight
[B] Mass/Length
[C] Mass/Volume
[D] Mass/Area
Show Answer
Correct Answer: C [ Mass/Volume ]
Notes:
Density is the ratio of mass to volume. It is a measure of material’s compactness. Density = Mass/Volume
24. What do we call the maximum velocity of a fluid in a tube for which the flow remains streamlined?
[A] Hyper velocity
[B] critical velocity
[C] stream velocity
[D] laminar velocity
Show Answer
Correct Answer: B [critical velocity]
Notes:
The maximum velocity of a fluid in a tube for which the flow remains streamlined is called its critical velocity.
25. What happens to the frequency of the pendulum if it is suspended from the ceiling of the lift moving downward with acceleration equal to acceleration due to gravity ?
[A] it increases
[B] it decreases
[C] No change
[D] No oscillation
Show Answer
Correct Answer: D [No oscillation]
Notes:
If the lift is moving down ward with acceleration a = g then frequency becomes zero. It means there will be no oscillation in a pendulum.
26. 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.
27. Which of these is NOT an example of Periodic motion?
[A] Revolution of earth around the sun
[B] Rotation of earth about its polar axis
[C] Motion of minute’s hand of a clock
[D] None of the above
Show Answer
Correct Answer: D [None of the above]
Notes:
Examples of Periodic motion: (i) Revolution of earth around the sun (period one year) (ii) Rotation of earth about its polar axis (period one day) (iii) Motion of hour’s hand of a clock (period 12-hour) (iv) Motion of minute’s hand of a clock (period 1-hour) (v) Motion of second’s hand of a clock (period 1-minute) (vi) Motion of moon around the earth (period 27.3 days)
28. Which of the following eaves will be produced on bombarding a metal target by high energy electrons?
[A] Gamma rays
[B] X rays
[C] Infra red
[D] Microwaves
Show Answer
Correct Answer: B [X rays]
Notes:
One common way to generate X-rays is to bombard a metal target by high energy electrons. X-rays covers wavelengths from about 10–8 m (10 nm) down to 10–13 m (10–4 nm).
29. What is the speed of sound in air at 0 ºC?
[A] 3 x 108 m/s
[B] 344 m/s
[C] 441m/s
[D] 331 m/s
Show Answer
Correct Answer: D [331 m/s]
Notes:
The speed of sound in air is 331 m/s at 0 ºC and 344 m/s at 22 ºC.
30. Which of the following sounds is produced by earthquakes before the main shock waves?
[A] low-frequency infrasound
[B] high-frequency ultrasound
[C] sounds between 200 Hz and 400 Hz
[D] None of the above
Show Answer
Correct Answer: A [low-frequency infrasound]
Notes:
Earthquakes produce low-frequency infrasound before the main shock waves begin which possibly alert the animals. It is observed that some animals get disturbed before earthquakes.
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