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.
31. What is the SI unit of pressure?
[A] Newton
[B] Weber
[C] Henry
[D] Pascal
Show Answer
Correct Answer: D [Pascal]
Notes:
The SI unit of pressure is the pascal (Pa), defined as the pressure exerted by a force of one newton per square meter. The pascal is used to measure the pressure of gases and liquids, such as the pressure of the air in a tire or the pressure of water in a pipe. It is also used to measure the strength of materials, such as the pressure that a building foundation can withstand. It is the base unit of pressure in the International System of Units (SI). Other units of pressure, such as the bar, the atmosphere, and the pound per square inch, can be converted to pascals.
32. What is the reason for formation of Mirage in desert?
[A] Refraction of light
[B] Reflection of light
[C] Total internal reflection of light
[D] Both Refraction and Total internal reflection of light
Show Answer
Correct Answer: D [Both Refraction and Total internal reflection of light]
Notes:
Mirage is formed due to both Refraction and Total internal reflection of light. A mirage is a naturally occurring optical phenomenon in which light rays bend to produce a displaced image of distant objects or the sky.
33. If the orbit of a planet is an ellipse, then what is the point at which the Sun is located called?
[A] Circumcentre
[B] Centre
[C] Focus
[D] Incentre
Show Answer
Correct Answer: C [Focus]
Notes:
Both the Sun and the planets move around each other with their center of mass lying at the focus of the elliptical orbits.
34. Which of the following conversions is used in Microphone?
[A] Sound waves are converted into electrical energy and then reconverted into sound after transmission
[B] Sound waves are directly transmitted
[C] Electrical energy is converted into sound waves directly
[D] Amplification is not required at all
Show Answer
Correct Answer: A [Sound waves are converted into electrical energy and then reconverted into sound after transmission]
Notes:
A microphone is colloquially named mic or mike. It is a device, a transducer that converts sound into an electrical signal.
35. Due to which of the following processes the atmospheric temperature increases at the higher altitudes?
[A] Convection
[B] Radiation
[C] Conduction
[D] Inversion
Show Answer
Correct Answer: A [Convection]
Notes:
As altitude increases, the downward force also decreases due to the decreased density of the molecules. The upper atmosphere temperature starts increasing with altitude, as air gets heated up directly by sun’s radiation (Convection).
36. Which one is the minimum possible temperature beyond which matter cannot be cooled?
[A] -98.10° C
[B] -100.00° C
[C] -273.15° C
[D] -459.40° C
Show Answer
Correct Answer: C [-273.15° C]
Notes:
At the physically impossible-to-reach temperature of zero kelvin, or minus 459.67 degrees Fahrenheit (minus 273.15 degrees Celsius), atoms would stop moving. As such, nothing can be colder than absolute zero on the Kelvin scale.
37. An object covers distance which is directly proportional to the square of the time. Its accelaration is
[A] increasing
[B] decreasing
[C] zero
[D] constant
Show Answer
Correct Answer: D [constant]
Notes:
When an object covers distance which is directly proportional to the square of the time, its acceleration is constant. This is seen in the cases of falling objects. This relation between time and distance was first observed by Galileo.
38. Which of the following have the same unit ?
[A] Work and power
[B] Torque and moment of inertia
[C] Work and torque
[D] Torque and angular momentum
Show Answer
Correct Answer: C [Work and torque]
Notes:
The SI unit of work is the Newton-metre or joule (J). A Newton metre is also the SI unit of torque (also called moment or moment of force).
39. 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:
40. A bomb explodes on the moon. You will hear its sound on earth after ______
[A] 20 minutes
[B] 2 hours 20 minutes
[C] 3.7 hours
[D] You cannot hear the sound of explosion
Show Answer
Correct Answer: D [You cannot hear the sound of explosion]
Notes:
The sound will never reach Earth because there are not enough molecules or atoms of matter per cubic centimetre of space to create the pressure waves in a medium that is a sound wave. In simple words, Sound propagation needs a medium. The people on the Earth can see the flash, but cannot hear any sound.
