Tag: standardized measurement

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Multiple choice physics measurements and units kinds of units fundamental quantities standardized measurement

Which of the following physical quantity is different form others ?

  1. Displacement

  2. Velocity

  3. Force

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

Displacement, force, and velocity are vector quantities as they require direction as well as the magnitude for their representation but the kinetic energy is a scalar quantity as it does not require direction for its representation.

Multiple choice physics measurements and units kinds of units fundamental quantities standardized measurement

Write the SI unit of the physical quantity having following dimensional formula
$\displaystyle [{ M }^{ 0 }{ L }^{ 2 }{ T }^{ -2 }{ K }^{ -1 }]$.

  1. $\displaystyle {m} { kg }^{ 2 }{ K }^{ -1 }$
  2. $\displaystyle {m} ^{2} { kg }^{ 2 }{ T }^{ -1 }$
  3. $\displaystyle {m} ^{2} { s }^{ -2 }{ K }^{ -1 }$
  4. $\displaystyle {m} ^{2} { kg }^{ 2 }{ K }^{ -1 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
SI unit of $M$ is $kg$, that of $L$ is $m$, $T$ is $s$ and temperature (K) is $K$.

So, SI unit of $[M^0L^2T^{-2}K^{-1}]$ is  $m^2s^{-2}K^{-1}$.
Multiple choice physics measurement of physical quantities kinds of units fundamental quantities standardized measurement

Dimensional analysis is the analysis of the relationships between different physical quantities by 

  1. identifying their fundamental dimensions

  2. units of measure

  3. tracking these dimensions as calculations or comparisons are performed.

  4. All of the above

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Dimensional analysis establishes the relation between the physical quantities by comparing the different quantities using their fundamental dimensions.

The dimensional analysis also makes use of the units to measure different quantities and the dimensional analysis is also helpful in performing several calculations.

Multiple choice physics measurement of physical quantities kinds of units fundamental quantities standardized measurement

A dimensionless quantity

  1. never has a unit

  2. always has unit

  3. may have a unit

  4. does not exit
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A dimensionless quantity is that is always independent of basic $7$ units:-meter, second, kilogram, Kelvin, Candela, ampere.

But it is not necessary. A dimensionless quantity is unitless. And eg, for this, is radian (unit of angle), which is dimensionless quantity because it is the ratio of two lengths.

Multiple choice physics measurements and units kinds of units fundamental quantities standardized measurement

Some physical quantities are given in Column I and some possible SI units in which these quantities may be expressed are given in Column II. Match the physical quantities in Column I with the units in Column II.

Column I Column II
i. $GM _eM _s$ a. (volt) (coulomb) (metre)
ii. $3RT/M$ b. $(kilogram)(metre)^3 (second)^2$
iii. $F^2/q^2B^2$ c. $(meter)^2 (second)^{-2}$
iv. $GM _e/R _e$ d. $(farad) (volt)^2 (kg)^{-1}$


where G is universal gravitational constant; $M _e$ mass of the earth; $M _s$, mass of sun; $R _e$ radius of the earth; R, universal gas constant;T, absolute temperature; M, molar mass, F, force; q, charge; B, magnetic field.

  1. $i \rightarrow b., ii \rightarrow c.,d., iii \rightarrow c.,d., iv \rightarrow c.,d.,$
  2. $i \rightarrow a., ii \rightarrow c.,d., iii \rightarrow c.,d., iv \rightarrow c.,d.,$
  3. $i \rightarrow d., ii \rightarrow c.,d., iii \rightarrow c.,d., iv \rightarrow c.,d.,$
  4. $i \rightarrow c., ii \rightarrow c.,b., iii \rightarrow c.,d., iv \rightarrow c.,d.,$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

i. GM_eM_s is energy related (potential), ii. 3RT/M is velocity squared (m^2/s^2), iii. F^2/q^2B^2 is velocity squared, iv. GM_e/R_e is velocity squared. Matching these to the provided units leads to B.

Multiple choice physics measurement of physical quantities kinds of units fundamental quantities standardized measurement

Pressure (P), density $\displaystyle (\rho )$ and velocity (V) be taken as fundamental quantities for dimensional analysis.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Pressure is calculated as   $P = \dfrac{Force}{Area}$
Density  $\rho = \dfrac{Mass}{Volume}$

Velocity  $V = \dfrac{Displacement}{time}$

So, pressure, density and velocity are derived from other quantities and so, these are termed as derived quantities , not fundamental quantities.
Hence, the given statement is false.