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. These questions are part of GKToday’s 35000+ MCQs Bank Course in GKToday Android App
31. Which among the following methods is used in the nuclear power reactors to produce energy for peaceful purpose?
[A] Nuclear fusion
[B] Nuclear fission
[C] Radioactive decay
[D] None of the above
Show Answer
Correct Answer: B [Nuclear fission]
Notes:
Nuclear energy can be harnessed by two methods namely nuclear fusion and nuclear fission. Nuclear fission involves breaking of a large nucleus into two or more nuclei where as nuclear fusion is the process of fusing (merging) two lighter nuclei. Fusion reaction releases enormous amount of energy (under high temperature and pressure) and is uncontrollable and hence it is not preferred in nuclear reactors.
Note: Nuclear fusion powers Sun and all the stars.
Extra info: Hydrogen bomb uses the process of nuclear fusion and hence it is the most powerful bomb.
32. The speed of light in air is
[A] 3 × 108 m/s
[B] 4 × 108 m/s
[C] 5 × 108 m/s
[D] Infinity
Show Answer
Correct Answer: A [3 × 108 m/s]
Notes:
The speed of light c is exactly equal to 299,792,458 metres per second.
33. The absolute zero is a temperature at which__?
[A] molecular motion in a gas would cease
[B] water freezes
[C] all gases become liquid
[D] all gases become solid
Show Answer
Correct Answer: A [molecular motion in a gas would cease]
Notes:
Absolute zero is the lowest possible temperature at which all atomic or molecular motion in matter stops. By international agreement, absolute zero is defined as precisely; 0 K on the Kelvin scale, which is a thermodynamic (absolute) temperature scale; and .273.15 degrees Celsius on the Celsius scale.
34. Because of which of the following, a man standing close to the platform at a railway station experiences a pulling force towards a fast moving train?
[A] gravitational force between train and man
[B] illusion of the man
[C] the centripetal force
[D] pressure difference due to fast moving air in between
Show Answer
Correct Answer: D [pressure difference due to fast moving air in between]
Notes:
When a fast-moving train passes a man standing on the platform at rest, the air between train and person also moves with greater speed. This rapidly moving air, by Bernoulli’s principle will have a lower pressure than the still air a few feet away. The still air, having higher pressure, and being behind the man standing close will tend to push him toward the train.
35. What does the slope of a Distance-Time graph show?
[A] acceleration
[B] momentum
[C] mass
[D] speed
Show Answer
Correct Answer: D [speed]
Notes:
Distance-time graph is the plot of distance travelled by a body against time. Distance is plotted on the Y-axis (left) and Time is plotted on the X-axis (bottom). The slope of the graph indicates the speed of the object. ‘Straight lines’ on a distance-time graph tell us that the object is travelling at a constant speed.
36. A liquid disturbed by stirring comes to rest due to__:
[A] density
[B] surface tension
[C] viscosity
[D] centripetal force
Show Answer
Correct Answer: C [viscosity]
Notes:
The viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. It is due to friction between neighboring particles of the fluid that are moving at different velocities. Therefore, a liquid disturbed by stirring comes to rest dece its viscosity.
37. A cycle tyre bursts suddenly is an example of__:
[A] Isothermal process
[B] Adiabatic process
[C] Isochoric process
[D] Isoboric process
Show Answer
Correct Answer: B [Adiabatic process]
Notes:
When a tyre bursts suddenly energy is not immediately transferred between the system and the surrounding. So, the process is adiabatic. The sudden expansion of its air into the atmosphere is adiabatic and the tyre is cooled. In adiabatic process, heat neither enters the system nor leaves the system.
38. In which form, the supplied heat energy is stored during change in temperature of substance?
[A] Heat energy
[B] Kinetic energy
[C] Potential energy
[D] Both kinetic and potential energy
Show Answer
Correct Answer: B [Kinetic energy]
Notes:
Temperature is used as a measure for heat in an object by measuring the amount of kinetic energy in the molecules that make up the object. It is a measure of the average kinetic energy of the random molecular motion. Heat is a form of energy that can be transferred from the heat source to the molecules, and it can also change its form from heat to movement. The molecules that gain extra energy will have a higher frequency than the molecules that have not gained the extra energy.
39. What is the distance between a crest and a consecutive trough in a transverse wave ?
[A] Wavelength
[B] Amplitude
[C] Half of the wavelength
[D] Twice of wavelength
Show Answer
Correct Answer: C [Half of the wavelength]
Notes:
Wavelength is defined as distance between two consecutive crest or troughs. Between two crests, there is a trough exactly in the middle of the two crests. Distance between crest and adjacent trough will be half of the distance between two crests or simply, half of the wavelength.
40. What is the minimum distance (in metres) required to hear an echo?
[A] 10
[B] 13
[C] 17
[D] 21
Show Answer
Correct Answer: C [17]
Notes:
The human ear cannot distinguish echo from the original direct sound if the delay is less than 1/15 of a second. The velocity of sound in dry air is approximately 343 m/s at a temperature of 25°C. Therefore, the reflecting object must be more than 17.2m from the sound source for echo to be perceived by a person located at the source.
