Physics for Defence Warriors set 4 ( NDA / CDS / AFCAT )

• 0 Questions answered correctly
• 0 Questions answered incorrect
• 15 Questions unattempted

• 1

  1. What is the unit of atmospheric pressure?

  • A

    A. Bar
     

  • B

    B. Knot
     

  • C

    C. Joule
     

  • D

    D. Ohm

  Explanation

  Bar is the unit of atmospheric pressure. It is not a part of SI unit, it is the metric unit of pressure. The bar is still used in descriptions of pressure because it is about the same as atmospheric pressure.

• 2

  2. 

  

   

  • A

    A.

  • B

    B.

  • C

    C.

  • D

    D.

  Explanation

  Dobson is the unit of measuring the thickness of ozone layer. Dobson Unit (DU) is defined to be 0.01 mm thickness at STP (Standard temperature and Pressure). The unit is named after G.M.B. Dobson (Gordon Miller Bourne Dobson), one of the first scientists to investigate atmospheric ozone. One Dobson unit is equivalent to molecules of ozone per square metre.

• 3

  3. Electron volt ( eV ) is a unit of 

  • A

    A. energy
     

  • B

    B. charge
     

  • C

    C. potential difference
     

  • D

    D. magnetic force

  Explanation

  Electron volt ( eV ) is the unit of energy. It is the amount of energy which an electron acquires when accelerated through a potential difference of 1 V . Its value is approximately equals to .

• 4

  

  • A

    A.

  • B

    B.

  • C

    C.

  • D

    D.

  Explanation

  The correct matching is A-2, B-1, C-4, D-3.
  Unit of weight is Newton.
  Unit of volume of Cubic metre.
  Unit of temperature is Kelvin.
  Unit of pressure is Pascal.

• 5

  

  • A

    A.

  • B

    B.

  • C

    C.

  • D

    D.

  Explanation

  The correct matching is A-4, B-3, C-2, D-1. SI unit of power is or watt. Knot is the unit of measuring speed of a ship. Nautical mile is a unit of distance used by navigators in the sea. Calorie is a unit of heat. One calorie is equal to 4.18 J of energy.

• 6

  6. 

  

  • A

    A.

  • B

    B.

  • C

    C.

  • D

    D.

  Explanation

  The correct matching is A-3, B-4, C-2, D-1. Cusec is the unit used to measure rate of flow of water.
  A byte is the basic unit of information in computer storage and processing.
  Richter scale is used for measuring the intensity of earthquake.
  Bar is the unit of pressure.

• 7

  7. 

  

  • A

    A.

  • B

    B.

  • C

    C.

  • D

    D.

  Explanation

  The correct matching is A-1, B-2, C-3, D-4.
  High speed (supersonic sound) is measured in mach number. One mach number is the ratio of speed of moving object to the speed of sound.
  Wavelength is measured in angstrom ( ). 1 angstrom ( ) is equivalent to .
  The SI unit of pressure is pascal. 1 pascal is equivalent to bar.
  The SI unit of energy is joule.

• 8

  8. The dimension [ ] corresponds to

  • A

    A. force
     

  • B

    B. work done
     

  • C

    C. acceleration
     

  • D

    D. velocity

  Explanation

  

• 9

  9. Which of the following is not correctly matched?

  

  • A

    A.

  • B

    B.

  • C

    C.

  • D

    D.

  Explanation

  Galvanometer is a device which is used to detects small current flowing in the circuit. The current and its intensity are usually indicated by a magnetic needle's movement or that of a coil in a magnetic field which is an important part of a galvanometer.

• 10

  10. 

  

  • A

    A.

  • B

    B.

  • C

    C.

  • D

    D.

  Explanation

  The correct matching is A-4, B-3, C-2, D-1. Hydrophone is a underwater device that detects and records ocean sounds from all directions.
  A megaphone increases the volume of sound by increasing the acousting impedance seen by the vocal cords. Thus, it is used to spreads sound to far-off places.
  Anemometer is a device that measures the wind speed.
  Tachometer is a device used to measure the rotation of shaft or a disk.

• 11

  11. In SONAR, we use

  • A

    A. radio waves
     

  • B

    B. audible sound waves
     

  • C

    C. ultrasonic waves
     

  • D

    D. infrasonic waves

  Explanation

  In SONAR, we use ultrasonic waves. It is because, it can penetrates water too long distances due to its high frequency. It also does not scatter very much.

• 12

  12. SONAR is mostly used by

  • A

    A. astronauts
     

  • B

    B. doctors
     

  • C

    C. engineers
     

  • D

    D. navigators

  Explanation

  SONAR is mostly used by navigators. The navigators plans and charts the course and the points the boat in the right direction using SONAR technique.

• 13

  13. The instruments, used for measuring angular distances in vertical plane (elevation) and the horizontal plane (azimuth), is 

  • A

    A. bevel protractor
     

  • B

    B. altimeter
     

  • C

    C. syncline
     

  • D

    D. theodolite

  Explanation

  Theodolite is an optical device which is used to measure angular distances between designated visible points in the horizontal and vertical planes.

• 14

  14. 

  

  • A

    A.

  • B

    B.

  • C

    C.

  • D

    D.

  Explanation

  The correct matching is A-4, B-1, C-2, D-3. Fathometer is a device use to measure the depth of water or a submerged object by means of ultrasonic waves. The barometer is used to measure atmospheric pressure, hygrometer is used to measure humidity and altimeter is used to measure altitude/ height of an object above certain level.

• 15

  15. Which one of the following is not correctly matched?

  • A

    A. Manometer - Pressure
     

  • B

    B. Carburetor - Internal combustion engine
     

  • C

    C. Cardiograph - Heart movement
     

  • D

    D. Seismometer - Curvature of surface

  Explanation

  Seismometer is an instrument used to measure seismic waves generated by earthquakes. Carburetor is an instrument that blends air and fuel for an internal combustion engine. Cardiograph is a device used to record the mechanical movements of the heart. Manometer is an instrument used to measure pressure.