__Units and Measurements MCQs:__

- Physics is a quantitative science, based on the measurement of physical quantities. Certain physical quantities have been chosen as fundamental or base quantities (such as length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity).

- Each base quantity is defined in terms of a certain basic, arbitrarily chosen but properly standardized reference standard called unit (such as meter, kilogram, second, ampere, kelvin, mole, and candela). The units for the fundamental or base quantities are called fundamental or base units.

- Other physical quantities, derived from the base quantities, can be expressed as a combination of the base units and are called derived units. A complete set of units, both fundamental and derived, is called a system of units.

- The International System of Units (SI) based on seven base units is at the present an internationally accepted unit system and is widely used throughout the world.

- The SI units are used in all physical measurements, for both the base quantities and the derived quantities obtained from them. Certain derived units are expressed using SI units with special names (such as joule, newton, watt, etc).

- The SI units have well-defined and internationally accepted unit symbols (such as m for meter, kg for kilogram, s for a second, A for ampere, N for newton, etc.).

- Physical measurements are usually expressed for small and large quantities in scientific notation, with powers of 10. Scientific notation and prefixes are used to simplify measurement notation and numerical computation, giving an indication of the precision of the numbers.

- Certain general rules and guidelines must be followed for using notations for physical quantities and standard symbols for SI units, some other units, and SI prefixes for expressing properly the physical quantities and measurements.

- In computing any physical quantity, the units for derived quantities involved in the relationship(s) are treated as though they were algebraic quantities till the desired units are obtained.

- Direct and indirect methods can be used for the measurement of physical quantities.

__MCQ on Unit and Measurement:__**1. The base quantity among the following is________**

(1) Speed

(2) Weight

(3) Length

(4) Area

**Answer:**(3)There are seven base quantities,

(i) Mass

(ii) Length

(iii) Time

(iv) Current

(v) Amount of substance

(vi) Luminous intensity

(vii) Temperature

**2. Which of the following is not a unit of time?**

(1) Second

(2) Minute

(3) Hour

(4) Light year

__Answer: (4)__A light year is the unit of distance

1 light year = 9.46 × 1015 m

**3. One astronomical unit is a distance equal to______**

(1) 9.46 × 1015 m

(2) 1.496 × 1011 m

(3) 3 × 108 m

(4) 3.08 × 10¹6 m

__Answer: (2)__**4. Ampere second is a unit of______**

(1) Current

(2) Charge

(3) Energy

(4) Power

__Answer: (2)__**5. The most precise reading of the mass of an object, among the following is__________**

(1) 20 g

(2) 20.0 g

(3) 20.01 g

(4) 20 × 100 g

__Answer: (3)__**6. The most accurate reading of the length of a 6.28 cm long fiber is___**

(1) 6 cm

(2) 6.5 cm

(3) 5.99 cm

(4) 6.0 cm

__Answer: (2)__**7. Which of the following is a unit that of force?**

(1) N m

(2) mN

(3) nm

(4) N s

__Answer: (2)__**8. The number of significant figures in a pure number 410 is_______**

(1) Two

(2) Three

(3) One

(4) Infinite

__Answer: (4)__**9. Thickness of a pencil measured by using a screw gauge (least count .001 cm) comes out to be 0.802 cm. The percentage error in the measurement is______**

(1) 0.125%

(2) 2.43%

(3) 4.12%

(4) 2.14%

__Answer: (1)__**10. The relative error in the measurement of the side of a cube is 0.027. The relative error in the measurement of**

**its volume is__________**

(1) 0.027

(2) 0.054

(3) 0.081

(4) 0.046

**(3)**

__Answer:__**11. Zero error in an instrument introduces______**

(1) Systematic error

(2) Random error

(3) Least count error

(4) Personal error

**(1)**

__Answer:__**12. A packet contains silver powder of mass 20.23 g ± 0.01 g. Some of the powder of mass 5.75 g ± 0.01 g is**

**taken out from it. The mass of the powder left back is________**

(1) 14.48 g ± 0.00 g

(2) 14.48 ± 0.02 g

(3) 14.5 g ± 0.1 g

(4) 14.5 g ± 0.2 g

__Answer: (2)__m1 = 20.23 g ± 0.01 g

m2 = (5.75 ± 0.01) g

m1 – m2 = [(20.23 – 5.75) ± 0.02] g

m (14.48 0.02) g

**13. The addition of three masses 1.6 g, 7.32 g, and 4.238 g, addressed up to proper decimal places is________**

(1) 13.158 g

(2) 13.2 g

(3) 13.16 g

(4) 13.15 g

**(2)**

__Answer:__**14. We can reduce random errors by___________**

(1) Taking a large number of observations

(2) Corrected zero error

(3) By following the proper technique of experiment

(4) Both (1) & (3)

**(1)**

__Answer:__**15. The number of significant figures in the measured value of 0.0204 is_______**

(1) Five

(2) Three

(3) Four

(4) Two

**(2)**

__Answer:__**16. The number of significant figures in the measured value of 26000 is_______**

(1) Five

(2) Two

(3) Three

(4) Infinite

**(2)**

__Answer:__The trailing zeros are not significant.

So, only two digits are significant.

**Read**:

**Chapter 2: Mathematical Methods MCQs****Chapter 3. Motion in plane MCQ****Chapter 5: Gravitation MCQs****Chapter 10: Electrostatics MCQs****Chapter 12: Magnetism MCQs****Chapter 15: Semiconductors MCQs**

**17. The number of significant zeroes present in the measured value of 0.020040, is__**

(1) Five

(2) Two

(3) One

(4) Three

**(4)**

__Answer:__Zeroes appearing between and after non-zero numbers are significant.

0.020040

**18. The number of significant figures in the measured value of 4.700 m is the same as that in the value______**

(1) 4700 m

(2) 0.047 m

(3) 4070 m

(4) 470.0 m

**(4)**

__Answer:__4.700 Four significant figures.

Also, 470.0 m four significant figures.

**19. If a calculated value of 2.7465 g contains only three significant figures, the two insignificant digits in it are_______**

(1) 2 and 7

(2) 7 and 4

(3) 6 and 5

(4) 4 and 6

**(3)**

__Answer:__2.7465 g Last two digits are most insignificant.

**20. Round off the value 2.845 to three significant figures______**

(1) 2.85

(2) 2.84

(3) 2.80

(4) 2.83

**(2)**

__Answer:__**21. A length of 5.997 m rounded off to three significant figures is written as________**

(1) 6.00 m

(2) 5.99 m

(3) 5.95 m

(4) 5.90 m

**(1)**

__Answer:__**22. The order of the magnitude of the speed of light in the SI unit is_____**

(1) 16

(2) 8

(3) 4

(4) 7

**(2)**

__Answer:__**23. The values of several quantities are used in a mathematical formula. The quantity that should be most**

**precise and accurate in measurement is the one_________**

(1) Having the smallest magnitude

(2) Having the largest magnitude

(3) Used in the numerator

(4) Used in the denominator

**(1)**

__Answer:__**24. The dimensional formula for energy is__________**

(1) [MLT–2]

(2) [ML2T–2]

(3) [M–1L2T]

(4) [M L2 T]

**(2)**

__Answer:__**25. The pair of the quantities having the same dimensions is______**

(1) Displacement, velocity

(2) Time, frequency

(3) Wavelength, focal length

(4) Force, acceleration

**(3)**

__Answer:__**26. The uncertain digit in the measurement of a length reported as 41.68 cm is_______**

(1) 4

(2) 1

(3) 6

(4) 8

**(4)**

__Answer:__41.68 cm

**27. We can reduce random errors by________**

(1) Taking a large number of observations

(2) Corrected zero error

(3) By following the proper technique of experiment

(4) Both (1) & (3)

**(1)**

__Answer:__**28. The number of significant figures in the measured value of 0.0204 is_________**

(1) Five

(2) Three

(3) Four

(4) Two

**(2)**

__Answer:__The non-zero digits after the decimal places are significant.

**29. The number of significant figures in the measured value of 26000 is_______**

(1) Five

(2) Two

(3) Three

(4) Infinite

**(2)**

__Answer:__The trailing zeros are not significant. So, only two digits are significant.

**30. The number of significant zeroes present in the measured value of 0.020040, is_______**

(1) Five

(2) Two

(3) One

(4) Three

**(4)**

__Answer:__Zeros appearing between and after non-zero numbers are significant.

0.020040

**31. The number of significant figures in the measured value of 4.700 m is the same as that in the value______**

(1) 4700 m

(2) 0.047 m

(3) 4070 m

(4) 470.0 m

**(4)**

__Answer:__4.700 Four significant figures. Also, 470.0 m is four significant figures.

**32. If a calculated value of 2.7465 g contains only three significant figures, the two insignificant digits in it are_______**

(1) 2 and 7

(2) 7 and 4

(3) 6 and 5

(4) 4 and 6

**(3)**

__Answer:__**33. The exchange particles responsible for weak interactions are_______**

(1) Gluons

(2) A-mesons

(3) Photons

(4) W and Z bosons

**(4)**

__Answer:__Weak interaction takes place through the exchange of BOSONS W and Z bosons

**34. Maxwell unified__________**

(1) Electricity with gravitation

(2) Electricity with magnetism

(3) Electromagnetism with optics

(4) Electromagnetism with weak interaction

**(3)**

__Answer:__Maxwell unified electromagnetism with optics.

**35. Which of the following is not a derived force**?

(1) Tension in a string

(2) van der Waal forces

(3) Nuclear force between proton-proton

(4) Electrostatic force between proton-proton

**(4)**

__Answer:__The electrostatic force between proton-proton is a fundamental force.

**36. Which one of the following does not experience strong nuclear force?**

(1) Leptons

(2) Baryons

(3) Hadrons

(4) Proton

**(1)**

__Answer:__Leptons don't experience strong nuclear force.

**37. Which pair do not have equal dimensions?**

(1) Energy and torque

(2) Force and impulse

(3) Angular momentum and Planck’s constant

(4) Elastic modulus and pressure

Force [MLT–2]

Impulse [MLT–1]

(1) Energy

**(2)**__Answer:__Force [MLT–2]

Impulse [MLT–1]

**38. The dimensions of Planck’s constant are equal to that of_______**(1) Energy

(2) Momentum

(3) Angular momentum

(4) Power

(1) Unit of time is doubled

(2) Unit of mass is doubled

(3) Unit of momentum is doubled

(4) Unit of energy is doubled

(1) It May be true

(2) May be false

(3) Must be true

(4) Must be false

This statement is completely correct. If a quantity depends upon two other quantities which are dimensionally the same then the formula's validity can be checked but it can't be derived by the method of dimensions.

(1) time

(2) distance

(3) sunlight intensity

(4) mass

(1) [MLT]

(2) [ML2T-1]

(3) [M2L2T-1]

(4) [ML1T-1]

(1) 70 N/m

(2) 7 ✕ 10-2 N/m

(3) 7 ✕ 102 N/m

(4) 7 ✕ 103 N/m

(1) Force

(2) Pressure

(3) Work

(4) Momentum

(1) 10-3 kg m-3

(2) 10-2 kg m-3

(3) 10 kg m-3

(4) 103 kg m-3

(1) 3.6 ✕ 108 J

(2) 3.6 ✕ 102 J

(3) 3.6 ✕ 103 J

(4) 10-3 J

(1) Specific Heat and Latent Heat

(2) Impulse and Momentum

(3) Surface Tension and Force

(4) Moment of Inertia and Torque

(a) [M1L1T-1]

(b) [M1L-5T1]

(c) [M2L5T-1]

(d) [M1L5T-2]

(1) Charge

(2) Potential difference

(3) Energy

(4) Magnetic Force

(1) 0.05 cm

(2) 0.5 cm

(3) 5.0 cm

(4) 0.005 cm

**(3)**__Answer;__**39. The unit of length, velocity, and forces is doubled. Which of the following is the correct change in the other****units**?(1) Unit of time is doubled

(2) Unit of mass is doubled

(3) Unit of momentum is doubled

(4) Unit of energy is doubled

**(3)**__Answer:__**40. Even if a physical quantity depends upon three quantities, out of which two are dimensionally the same, then****the formula cannot be derived by the method of dimensions. This statement__________**(1) It May be true

(2) May be false

(3) Must be true

(4) Must be false

**(3)**__Answer:__This statement is completely correct. If a quantity depends upon two other quantities which are dimensionally the same then the formula's validity can be checked but it can't be derived by the method of dimensions.

**41. A light year is a unit of________**(1) time

(2) distance

(3) sunlight intensity

(4) mass

**(2) distance**__Answer:__**42. The dimensional formula for Planck’s constant is________**(1) [MLT]

(2) [ML2T-1]

(3) [M2L2T-1]

(4) [ML1T-1]

**(2) [ML2T-1] (Hint use E = hν)**__Answer:__**43. The surface tension of a liquid is 70 dyne/cm. In the MKS system, its value is?**(1) 70 N/m

(2) 7 ✕ 10-2 N/m

(3) 7 ✕ 102 N/m

(4) 7 ✕ 103 N/m

**(2) 7 ✕ 10-2 N/m**__Answer:__**44. The dimensions of Kinetic energy are the same as that of_______**(1) Force

(2) Pressure

(3) Work

(4) Momentum

**(3) Work**__Answer:__**45. At 4°C, the density of water is equal to______**(1) 10-3 kg m-3

(2) 10-2 kg m-3

(3) 10 kg m-3

(4) 103 kg m-3

**(4) 103 kg m-3**__Answer:__**46. One-watt hour contains how many joules?**(1) 3.6 ✕ 108 J

(2) 3.6 ✕ 102 J

(3) 3.6 ✕ 103 J

(4) 10-3 J

**(3) 3.6 ✕ 103 J**__Answer:__**47. Which of the following pairs has the same dimensions?**(1) Specific Heat and Latent Heat

(2) Impulse and Momentum

(3) Surface Tension and Force

(4) Moment of Inertia and Torque

**(2) Impulse and Momentum**__Answer:__**48. The equation of state of some gases can be expressed as Vander wal equation i.e.****(P + a/v2)(V – b) = RT****Where P is the pressure, V is the volume, T is the absolute temperature and a, b, and R are****constants. The dimensions of ‘a’ are:**(a) [M1L1T-1]

(b) [M1L-5T1]

(c) [M2L5T-1]

(d) [M1L5T-2]

**(4) [M1L5T-2]**__Answer:__**49. Electron volt is a unit of_______**(1) Charge

(2) Potential difference

(3) Energy

(4) Magnetic Force

**(3) Energy**__Answer:__**50. There are 20 divisions in 4 cm of the main scale. The vernier scale has 10 divisions. The least count of the instrument is________**(1) 0.05 cm

(2) 0.5 cm

(3) 5.0 cm

(4) 0.005 cm

**) 0.005 cm**__Answer:__(4__Physics Related Articles:__