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.
1. Mach number is a measure of which of the following?
[A] Speed
[B] Heat Transfer
[C] Static Pressure
[D] Volume
Show Answer
Correct Answer: A [Speed]
Notes:
Mach number refers to the ratio of the velocity of a fluid to the velocity of sound in that fluid, named after Ernst Mach (1838–1916), an Austrian physicist and philosopher. Speed of sound is Mach 1 speed.
2. Which among the following Radio frequencies are used around the world in air navigational system?
[A] Very Low Frequency (VLF)
[B] Very High Frequency (VHF)
[C] Tetrahertz Radiation (THF)
[D] Ultra High Frequency (UHF)
Show Answer
Correct Answer: B [ Very High Frequency (VHF)]
Notes:
VHF (Very High Frequency) omnidirectional radio range (VOR), is a short-range radio navigation system for aircraft, enabling aircraft to determine their position and stay on course by receiving radio signals transmitted by a network of fixed ground radio beacons, with a receiver unit. Uses radio frequencies in the very high frequency (VHF) band from 108 to 117.95 MHz. VOR is the standard air navigational system in the world, used by both commercial and general aviation.
3. Which of the following makes a CD or DVD show rainbow pattern?
[A] Diffraction of the Light
[B] Thin-Film Interference of the light
[C] Scattering of the light
[D] Polarisation of the light
Show Answer
Correct Answer: A [ Diffraction of the Light]
Notes:
A CD or DVD has closely spaced tracks which work as a diffraction grating to form the familiar rainbow pattern seen when looking at a disk.
4. Which of the following is correct about the properties of Gravitational Forces?
[A] They are the strongest forces in nature
[B] They observe inverse square law
[C] Both a and b
[D] None
Show Answer
Correct Answer: B [They observe inverse square law]
Notes:
Gravitational Forces are the weakest forces in nature. They obey inverse square law as they vary inversely as the square of the distance between the two bodies. They are central forces and conservative forces. They operate over very long distances having an infinite range.
5. Who was the first scientist to discover Electrons?
[A] Albert Einstein
[B] Isaac Newton
[C] J.C. Bose
[D] J.J Thompson
Show Answer
Correct Answer: D [J.J Thompson]
Notes:
J.J Thompson was the first scientist to discover and identify the electrons and to make the discovery of the first subatomic particle. He was also the first scientist to find evidence for isotopes of a stable (non-radioactive) element in 1913, as part of his exploration into the composition of canal rays (positive ions). His experiments to determine the nature of positively charged particles led to the development of the mass spectrograph. J.J Thompson belonged to United Kingdom. He won the Nobel Prize in Physics in 1906 for his work on the conduction of electricity in gases.
6. Which of the following physical quantities has no units?
[A] Reynold Number
[B] Rydberg constant
[C] Wave number
[D] Hubble constant
Show Answer
Correct Answer: A [ Reynold Number ]
Notes:Reynold Number has no units. The Reynolds number is the ratio of inertial forces to viscous forces. It is used for predicting if a flow condition will be laminar or turbulent.
- Unit of Rydberg constant: m-1
- Unit of Wave number = m-1
- Unit of Hubble constant = sec-1
7. Which of the following conditions is true for an object to be in equilibrium?
[A] No linear motion of the object
[B] No rotational motion of the object
[C] Minimum potential energy of the object
[D] All of the above
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Correct Answer: D [All of the above]
Notes:
The conditions for equilibrium for an object: 1. There is no linear motion of the object i.e. the resultant force on the object is zero 2. There should not be any rotational motion of the object i.e. the torque on the object should be zero 3. The potential energy of the object should be minimum for stable equilibrium.
8. A projectile will achieve maximum horizontal range at which angle?
[A] 90°
[B] 60°
[C] 45°
[D] 30°
Show Answer
Correct Answer: C [45°]
Notes:
A projectile will achieve maximum horizontal range when it is projected at an angle of 45°. This concept of maximum horizontal range is used by athletes in long jump, javelin throw, cricket ball throw etc
9. What is the apparent weight of the person when the elevator is accelerating downwards?
[A] equal to the actual weight
[B] greater than the actual weight
[C] less than the actual weight
[D] 0
Show Answer
Correct Answer: C [less than the actual weight]
Notes:
The apparent weight of the person becomes less than the actual weight when the elevator is accelerating downwards. The apparent weight of the person becomes more than the actual weight when the elevator is accelerating upwards.
10. The value of coefficient of limiting friction does not depend on which of the following?
[A] nature of the surfaces in contact
[B] total area of the surfaces in contact
[C] material of the surfaces in contact
[D] All of the above
Show Answer
Correct Answer: B [total area of the surfaces in contact]
Notes:
The coefficient of static friction can be defined as the ratio of the limiting static friction and the normal reaction between the 2 surfaces. The value of coefficient of limiting friction depends: 1. Nature of the surfaces in contact. 2. Material of the surfaces in contact