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 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).

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

Which of the following pairs of physical quantities have same dimensions?

  1. Force and power

  2. Torque and energy

  3. Torque and power

  4. Force and torque
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Torque is the moment of force given by:$ \vec\tau=\vec r\times \vec F$

It’s unit is Newton-meter.

The unit of work/energy is also Newton-meter or Joule.

Thus, both of these physical quantities have the same units/dimensions.

$[Torque]=[M][L]^{2}[T]^{−2}=[Energy]$
Multiple choice physics motion and measurement physical quantities units - definitions and systems physical quantities like mass and weight

Which of the following statements is incorrect regarding mass. ?

  1. It is a basic property of matter.

  2. The SI unit of mass is kg.

  3. The mass of an atom is expressed in u.

  4. It depends upon the temperature, pressure or location of the object in space.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Mass is property of mater, which is independent of other properties like temperature, pressure or location of the object in space.

Multiple choice physics fluid pressure pressure in air introduction to atmospheric pressure pressure exerted by air devices to measure pressure

State the S.I. unit. of pressure

  1. Newton

  2. Pascal

  3. Coulomb

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

Pressure is defined as force per unit area. It is usually more convenient to use pressure rather than force to describe the influences upon fluid behavior. The standard unit for pressure is the Pascal, which is a Newton per square meter.

$1Pa=1Nm^{-2}$