Tag: measurements and units

Quizzes (10) Questions (257)

Questions Related to measurements and units

Multiple choice physics measurements and units some examples of derived units fundamental and derived quantities fundamental and derived units

Identify the derived quantities among the following.

  1. Gravitational constant

  2. Frequency

  3. Electric charge

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

The derived quantities are the one which depends on the other fundamental quantities for their representation. Among the following quantities, an electric current is a fundamental quantity whereas gravitational constant, frequency and electric charge are the derived quantities.

Multiple choice physics measurements and units some examples of derived units fundamental and derived quantities fundamental and derived units

Using dimensional analysis the resistivity in terms of fundamental constants $h, m _e, c, e, \varepsilon _o$ can be expressed as.

  1. $\displaystyle\frac{h}{\varepsilon _0m _ece^2}$
  2. $\displaystyle\frac{\varepsilon _0m _ece^2}{h}$
  3. $\displaystyle\frac{h^2}{m _ece^2}$
  4. $\displaystyle\frac{m _e\varepsilon _0}{ce^2}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

 SI base units of resistivity are written as $Kgm^3s^{-1}C^{-2}$.

For plank constant  $h$  SI base units are $Kgm^2s^{-1}$.
For $e$  SI unit is $C$.
For $c$  SI unit is $ms^{-1}$.
For $m _e$ SI unit is $Kg$.
For $\varepsilon _o$ SI unit is $C^2{Kg}^{-1}m^{-3}s^{2}$
Solving the dimensions of constants in option $C$,
$\dfrac{({Kgm^2s^{-1}})^2}{Kgms^{-1}C^2}=Kgm^3s^{-1}C^{-2}$
We get the dimensions of resistivity hence option $C$ is correct.

Multiple choice physics measurements and units some examples of derived units fundamental and derived quantities fundamental and derived units

Which of the following quantities has its unit as newton second?

  1. Energy

  2. Torque

  3. Momentum

  4. Angular momentum
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Dimensional formula of newton second $=\left[ \dfrac { kgm }{ { S }^{ 2 } } \times S \right] $

$=\left[ { MLT }^{ -1 } \right] $
Dimensional formula of momentum $=\left[ { MLT }^{ -1 } \right] $
Hence, momentum has the unit as $Nsec$.

Multiple choice physics measurements and units some examples of derived units fundamental and derived quantities fundamental and derived units

Among the following identify derived quantities?

  1. Speed

  2. Temperature

  3. Volume

  4. Mass
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation

(A) Speed $\displaystyle = \frac{distance}{time}$ - a derived quantity of length and time.
(B) Temperature - fundamental quantity.
(C) Volume (cube of length) - a derived quantity of length.
(D) Mass - fundamental quantity.

Multiple choice physics measurements and units some examples of derived units fundamental and derived quantities fundamental and derived units

Which of the following is larger unit of density ?

  1. $gm^{-3}$
  2. $gkm^{-3}$
  3. $kgm^{-3}$
  4. $gcm^{3}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
m is the mass of an object divided by its volume. Density often has units of grams per cubic centimeter (g/cm3). Remember, grams is a mass and cubic centimeters is a volume (the same volume as 1 milliliter).