Physics Objective (Multiple Choice) General Knowledge & General Science Questions & Answers for SSC-CGL, UPPSC, NDA, CDS and all one day examinations of India.
31. In which among the following mediums, the speed of sound is maximum?
[A] Vacuum
[B] Air
[C] Water
[D] Steel
Show Answer
Correct Answer: D [Steel]
Notes:
Sound being a longitudinal wave, its speed is directly proportional to the density of the medium. The denser the medium, the faster is the sound. Among the given options, density is more in steel and hence the speed of sound is more in steel compared to other three.
Extra info: Speed of sound in steel : 5960 mts/second.
Speed of sound in air: 330 mts/second.
Speed of sound in vacuum: 0 mts/second.
32. In 1922, Neils Bohr won Nobel Prize in which field?
[A] Mathematics
[B] Peace
[C] Physics
[D] Chemistry
Show Answer
Correct Answer: C [Physics]
Notes:
In 1922, Neils Henrik David Bohr won Nobel Prize in Physics for his remarkable contributions towards the understanding of the atomic structure and quantum theory. Neils Bohr was a Danish physicist born and died in Copenhagen, Denmark. He developed Bohr Model of the Atom, in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level to another.
33. The atmospheric air is held to the Earth by?
[A] gravity
[B] winds
[C] clouds
[D] rotation of the Earth
Show Answer
Correct Answer: A [gravity]
Notes:
The atmosphere is held in place on earth by gravity.
34. Which one of the following is a non-dimensional quantity?
[A] Gas constant
[B] Strain
[C] Co-efficient of viscosity
[D] Planck’s constant
Show Answer
Correct Answer: B [Strain]
Notes:
A dimensionless quantity is simply a quantity that has no units and therefore no dimensions. A ratio between two numbers is a non-dimensional or dimensionless quantity. Strain which is defined as change in dimension over original dimension has no dimensional formula. So, it is a dimensionless quantity.
35. The period of revolution of a certain planet in an orbit of radius R is T. Its period of revolution in an orbit of radius 4R will be:
[A] 8 T
[B] 4 T
[C] 2 2 T
[D] 2 T
Show Answer
Correct Answer: A [8 T]
Notes:
36. The time period of a sound wave is 0.01 seconds. What will be its frequency in Hz?
[A] 100
[B] 10
[C] 50
[D] 20
Show Answer
Correct Answer: A [100]
Notes:
Frequency is the number of wave cycles or revolutions per second. The formula for period (T) in terms of frequency is given by : f = 1/T According to question T = 0.01 seconds. So, f = 1/0.01 = 100/1 = 100 Hz
37. One nautical mile is equal to__:
[A] 2000 metres
[B] 1852 metres
[C] 1672 metres
[D] 2450 metres
Show Answer
Correct Answer: B [1852 metres]
Notes:
A nautical mile is a unit of measurement used in both air and marine navigation, and for the definition of territorial waters. The international nautical mile is defined as exactly 1852 metres. This converts to about 1.15 imperial/US miles. The derived unit of speed is the knot, one nautical mile per hour.
38. What is the unit of Momentum?
[A] Ampere
[B] Kg m/sec
[C] Joule
[D] Kg-m
Show Answer
Correct Answer: B [Kg m/sec]
Notes:
The unit of momentum is the product of the units of mass and velocity. In SI units, if the mass is in kilograms and the velocity is in meters per second then the momentum is in kilogram meters per second (kg m/s). The ampere is the SI base unit of electric current equal to one coulomb per second. The SI unit of energy is the joule. The kilogram per meter is a unit of measurement of linear density.
39. Why the Shock-absorbers are usually made of steel?
[A] Steel is not brittle
[B] Steel has lower elasticity
[C] Steel has higher elasticity
[D] Steel has no ductile property
Show Answer
Correct Answer: C [Steel has higher elasticity]
Notes:
A shock absorber is a mechanical device designed to smooth out or damp shock impulse, and dissipate kinetic energy. Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2.1% by weight, depending on the grade. Steel of varied grades is used in the manufacturing of shock absorbers because of their required high elasticity and ductility.
40. Kinetic energy depends on which of the following?
[A] the velocity or speed of the moving body.
[B] the mass of the moving body
[C] the pressure of the moving body
[D] both mass and velocity of the moving body
Show Answer
Correct Answer: D [both mass and velocity of the moving body]
Notes:
Kinetic energy is the energy associated with the movement of objects. The amount of kinetic energy that an object has depends upon two variables: the mass (m) of the object and the speed (v) of the object.
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