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 the essence of change different forms of energy energy conversions energy transformations and energy transfers

The units of fore and length are made three times of their earlier values. Earlier the energy of a system was $81\ J$. What will be the energy of the same system in new units?

  1. $243$
  2. $729$
  3. $9$
  4. $None\ of\ the\ above$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Energy has dimensions [M L^2 T^-2]. If force [M L T^-2] and length [L] are tripled, then [M L T^-2] -> 3 and [L] -> 3. This implies [M] -> 3 / 3 = 1 and [T^-2] -> 3 / 3 = 1 (no change). Thus, energy scales by [M] * [L]^2 * [T^-2] = 1 * 3^2 * 1 = 9. New energy = 81 * 9 = 729 J.

Multiple choice physics electrical circuits domestic electric circuits and safety precautions domestic and commercial circuit electric power

Units of power and voltage are represented by

  1. W, V

  2. A, V
  3. W, $\Omega$
  4. V, $\Omega$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In our every day lives we use electrical energy to do work for us. This electrical energy is provided either by our power company through the outlets in our wall, or we can buy stored electrical energy in the form of batteries. Different electrical appliances use electrical energy at different rates. Power is the rate at which work is done. The power rating of an appliance tells us the rate at which it uses electrical energy. For example, a 1500 watt hair dryer uses 1500 joules of electrical energy per second.
In any electrical appliance their is a simple relationship between the power output of a component, the potential difference across that component, and the current running through it. This is because charge times potential difference is energy, so (charge per unit time) times (potential difference) gives (energy per unit time).
Thus, we have $P=V I.$
Substituting $V=I R$ from ohm's law, the power relationship can be rewritten as $P={ I }^{ 2 }R$. From this formula, the resistance can be calculated.

hence correct option is A

Multiple choice physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

The unit of frequency is:-

  1. Hertz

  2. Joule

  3. Ohm

  4. Kilo Calorie
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Frequency is the number of complete vibrational cycles of a medium per a given amount of time. The frequency would have units of cycles/second, waves/second or vibrations/second. The unit for frequency is the Hertz (abbreviated Hz) where 1 Hz is equivalent to 1 cycle/second. 

Multiple choice physics sound: production of sound oscillation - amplitude, time period and frequency of oscillation time period, frequency and amplitude of sound oscillatory and periodic motion

Hertz stands for:

  1. second
  2. second$^{-1}$

  3. meter
  4. meter$^{1}$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Hertz is the unit of frequency and frequency is defined as number of vibrations per second ,

        $f=$number of vibrations/ time (in second) ,
which gives frequency in,
$second^{-1}=Hertz$ 

Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

The SI unit of density is __________.

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

Density of substance is mass per unit volume hence its unit are $kg/{ m }^{ 3 }$ in S/units & $gm/{ cm }^{ 3 }$ in CGS.

Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

Mass per unit volume of a substance is called its density. True or false.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Density of substance is a characterstic property of a substance defined as mass of substance per unit volume.

density = $\dfrac { mass\quad of\quad substance }{ volume\quad of\quad substance } $.

Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

Define density.

  1. Density of a substance is defined as the weight per unit volume of that substance.

  2. Density of a substance is defined as the mass per unit volume of that substance.

  3. Density of a substance is defined as the volume per unit mass of that substance.

  4. Density of a substance is defined as mass times volume of the substance.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Density of a substance is defined as the mass per unit volume. Its SI unit is $kgm^{-3}$. For example, the density of water at room temperature and atmospheric pressure is $1\ kgm^{-3}$.

Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

Which of the following is true about the density of a substance?

  1. It is a derived quantity.
  2. The unit of density in SI system is kilogram per metre$^3$.

  3. The density of a substance can be measured if the mass of the substance for a certain volume is known.

  4. Density is a vector quantity
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

Let the mass of the substance be $m$ and its volume be $V$. Then the density of the substance is defined as the ratio of mass to the volume of the body.

Thus the density of a substance can be derived as  $\rho = \dfrac{m}{V}$

SI unit of mass is $kg$ and that of the volume is $m^3$. Thus SI unit of density is  $kg/m^3$.
The density of a substance is a scalar quantity, not a vector quantity as it has magnitude only.
Hence options A, B and C are correct.

Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

SI unit of density is ________ times its CGS unit.

  1. 1000

  2. 10

  3. 0.1

  4. 0.001
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

SI unit of density $=\dfrac { kg }{ { m }^{ 3 } } =\dfrac { 1000 }{ 10^6 } \dfrac { g }{ cc } $

                             $\dfrac { 1kg }{ { m }^{ 3 } } ={ 10 }^{ -3 }9/cc$

Multiple choice chemistry substances in the surroundings - their states and properties measurement of density properties of substances fundamental and derived units

Which of the following is true about the density of a substance?

  1. It is a derived quantity.
  2. The unit of density in SI system is kilogram per metre$^3$.

  3. The density of a substance can be measured if the mass of the substance for a certain volume is known.

  4. Density is a vector quantity.
Reveal answer Fill a bubble to check yourself
A,B,C Correct answer
Explanation

The density of a substance is defined as the mass of the substance per unit volume of the substance.
$\rho=\dfrac mV$

Its unit is $kg/m^3$

It is a derived quantity as it uses the unit of mass and the unit of length.
The unit of density in the SI system is kilogram per meter $^3$.
The density of a substance can be measured if the mass of the substance for a certain volume is known.