Physics · Science General

Units and Measurement

998 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.

SI fundamental unitsUnits of powerDerived quantities unitsThermal energy unitsVolume measurement unitsElectric current units

Units and Measurement Questions

Multiple choice physics measurements and units summary of si units fundamental quantities system of units

Which of the following does not has fundamental unit?

  1. Mass

  2. Time

  3. Force

  4. Electric current
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The fundamental units are defined arbitrarily and they are used to derive of others unit. Generally the most common fundamental units are mass, time, length and current.

As the unit of force can be derived from three fundamental units, mass, length and time so the force does not has fundamental unit.

Multiple choice physics measurements and units summary of si units fundamental quantities system of units

The SI unit of electron mobility is  :

  1. ${M^2}{S^{ - 1}}V - 1$
  2. $=m^2 s^{-1}V^{-1}$
  3. $m{s^{ - 1}}V$
  4. ${m^2}{s^{ - 2}}V$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Electron mobility:- It is the ratio of velocity to electric field.

$\mu=\dfrac{v _e}{E}$. . . . . . .(1)
SI unit of velocity, $v _e$ $=m/s$
SI unit of electric field, $E$ $=V/m$
From equation (1),
SI unit of electron mobility is $=\dfrac{m/s}{V/m}$
$=m^2/Vs$
$=m^2 s^{-1}V^{-1}$

Multiple choice physics measurements and units summary of si units fundamental quantities system of units

The dimensional formula of a physical quantity is $\displaystyle { M }^{ 1 }{ L }^{ 2 }{ T }^{ 3 }{ I }^{ -1 }$ .What is its SI unit?

  1. $\displaystyle { kg\quad m }^{ 2 }{ s }^{ 3 }{ A }^{ -1 }$
  2. $\displaystyle { kg\quad m }^{ 2 }{ s }^{ 2 }{ A }$
  3. $\displaystyle { kg\quad ms }^{ -3 }{ A }^{ 2 }$
  4. $\displaystyle { kg}^{2}{ m }^{ 2 }{ s }^{ 3}{ A }^{ -1 }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

SI unit of $M$ is $kg$, that of $L$ is $m$, $T$ is $s$ and $I$ is $A$.
So, SI unit of $[M^1L^2T^{3}I^{-1}]$ is  $kg \ m^2s^{3}A^{-1}$.

Multiple choice physics measurements and units summary of si units fundamental quantities system of units

Find the unit of the following derived quantities: 
(a) Force [Hint: Force = Mass $\times$ acceleration]
(b) Pressure $\left[Hint: Pressure =\frac{force}{Area}\right]$

  1. $kg\,m\,s^{-2}$ and $kg\,m^{-1}\,s^{-2}$
  2. $kg\,m\,s^{-1}$ and $Kg\,m^{-2}\,s^{-1}$
  3. $ N$ and $ Pa$

  4. None of these
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation
Force   $F = ma$
So, unit of force is  $kg \ m/s^2$
Newton $(N)$ is also the unit of force.
Pressure   $P = \dfrac{F}{A}$
Unit of pressure   $ = \dfrac{kg \ m/s^2}{m^2} = kg \ m^{-1}s^{-2}$
Also, pressure is measured in Pascal $(Pa)$.
Multiple choice evs magic with mirrors dual nature of light nature and sources of light theories on light

Which of the following is a unit for intensity of light?

  1. Candle power

  2. Lux

  3. Both A & B

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The SI unit of luminous intensity is the candela (cd), an SI base unit.
Also, unit for intensity of light are:
(i) Candle Power
(ii) Lux
Multiple choice physics dynamics - explaining motion system of unit summary of si units system of units

If unit of mass, length and time are tripled, then unit of energy becomes:

  1. $3$
  2. $\dfrac{1}{3}$
  3. $9$
  4. $\dfrac{1}{9}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Unit of Energy $kg\,m^2/s^2$

Unit of length $= m$ (metre)

Unit of mass $= kg$ (kilogram)

Unit of time $= s$ (second)


Thus unit of energy in terms of unit of mass, length and time is given by,

$Unit \,of\, Energy =\dfrac{(Unit\,of\,mass)\times(Unit\,of\,length)^2}{(Unit\,of\,time)^2}$

If the unit of mass, length and time are tripled the unit of energy will be,

$Unit \,of\, Energy =\dfrac{(3\times Unit\,of\,mass)\times(3\times Unit\,of\,length)^2}{(3\times Unit\,of\,time)^2}$

$Unit \,of\, Energy =3\times \dfrac{(Unit\,of\,mass)\times(Unit\,of\,length)^2}{(Unit\,of\,time)^2}$

$Unit\,of\,energy=3\times Unit\,of\,energy$

Therefore, if the unit of mass, length and time are tripled, the unit of energy will be, 3 times more than the original unit of energy.