Physics · Science General

Units and Measurement

1,044 Questions

Master the fundamentals of physics with these practice questions on units and measurement. The topics include fundamental SI units, derived quantities, and specific units for power, force, and light. These questions are essential for building a strong foundation for competitive exams.

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Units and Measurement Questions

Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

In the SI system, the unit of temperature is:

  1. Degree centigrade

  2. Kelvin

  3. Degree celsius

  4. Degree Fahrenheit
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The S.I. unit of temperature as per the International System of Units is Kelvin which is represented by the symbol $K$. The Kelvin scale is widely accepted or used in the field of science and engineering.

Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

What is the  $SI$  unit of permeability?

  1. Henry per metre

  2. Tesla metre per ampere

  3. Weber per ampere metre

  4. All the above units are correct
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Permeability (mu) is related to magnetic field intensity H and magnetic flux density B by B = mu*H. The SI unit of B is Tesla (T) and H is Ampere per metre (A/m), so mu = B/H has units of T/(A/m) = T*m/A. Henry per metre (H/m) is also a standard unit, and Weber per ampere metre (Wb/A*m) is equivalent to H/m.

Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

If E and H represent electric field and magnetic field intensity respectively, then E/H has unit of 

  1. Ampere

  2. Ohm

  3. Volt

  4. Joule
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The ratio of electric field intensity E (V/m) to magnetic field intensity H (A/m) is known as the intrinsic impedance of the medium. The unit is (V/m) / (A/m) = V/A, which is the definition of an Ohm.

Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

Which of the following is not the unit of surface tension ? 

  1. $newton/meter$
  2. $joule/(meter)^2$
  3. $kg/(second)^2$
  4. $watt/ meter$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Surface tension is force per unit length (N/m). Since N = kg*m/s^2, N/m = kg/s^2. Also, surface tension is energy per unit area (J/m^2). Watt/meter is power per unit length, which is not surface tension.

Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

To express all the physical quantities in SI units, we need 

  1. two fundamental units

  2. three fundamental units

  3. five fundamental units

  4. seven fundamental units
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

SI unit system contains seven fundamental quantities which are independent to each other and can be used to represent any given quantity. Hence, all physical quantities can be represented in powers of seven fundamental SI units.

Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

In a system of units, the units of mass, length and time are called pail, jack, and jill. 1 pail = 5 kg, 1 m = 5 jacks and 24 s make 1 jill. What are the unit of density and speed in the new system?

  1. $\displaystyle { (pails)\quad (jills) }^{ -2 }$
  2. $\displaystyle { (pails)\quad (jack) }^{ -3 }$
  3. $\displaystyle { (jack) }^{ 2 }(jill)$
  4. $\displaystyle { (pails)\quad (jack) }^{ 2 }$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The unity of density$=\frac { unit\quad of\quad mass }{ { (unit\quad of\quad length) }^{ 3 } } \ =(pails){ (Jack) }^{ 3 }$

Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

The value of $\displaystyle G=6.67\times { 10 }^{ -11 } N \ { m }^{ 2 } kg^{ -2 } and \ g={ 9.8ms }^{ -2 }$, what is the unit of g/G in C.G.S system?

  1. $\displaystyle { g\quad cm }^{ -2 }$
  2. $\displaystyle { g\quad cm }^{ 2 }$
  3. $\displaystyle { g\quad cm }^{ -1 }$
  4. $\displaystyle { g\quad cm }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Unit of $g$ in SI is  $ms^{-1}$ and that of $G$ is $Nm^2 kg^{-2}$.
where  $1 \ N   = 1 \ kg \ ms^{-2}$ (in MKS system)

So, MKS units of $G$ is $m^3s^{-2}kg^{-1}$

Thus CGS unit of $g$ is  $cm \ s^{-2}$ and that of $G$ is $cm^3 s^{-2} g^{-1}$

Thus CGS unit of  $g/G$ is $g \ cm^{-2}$
Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

The  SI unit of weight is.

  1. kg wt

  2. N

  3. g wt

  4. all the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The weight of a body is , as the force with which the earth attracts it towards the centre.

$W= \dfrac{GMm}{R^2 }= mg$

$g$ (acceleration due to gravity) $= \dfrac{GM}{R^2}$

where,

$G$ is constant of gravitation, $R$ is distance from the centre if the earth, $M$ is the mass of the earth.

If the mass of the body $‘m'$ , the force of attraction of the earth or the $‘W'$ of the body is

$W= mg$

Weight is the force of attraction, its S.I. unit is same as that of S.I. unit of force .

The S.I. unit of weight is Newton (N).