Tag: fundamental quantities

Questions Related to fundamental quantities

A dimensionless quantity

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

  1. never has a unit

  2. always has unit

  3. may have a unit

  4. does not exit

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Correct Option: C
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.

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.

physics measurements and units kinds of units fundamental quantities standardized measurement

  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. $i \rightarrow c., ii \rightarrow c.,b., iii \rightarrow c.,d., iv \rightarrow c.,d.,$

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Correct Option: B

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

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

  1. True

  2. False

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Correct Option: B
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.

$S.I$unit of conductivity is 

physics measurements and units kinds of units fundamental quantities standardized measurement

  1. $siemens / meter$

  2. $siemens \times meter$

  3. $meter \times siemens$

  4. ${m}^{2}/ohm$

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Correct Option: A
Explanation:

Conductivity (or specific conductance) of an electrolyte solution is a measure of its ability to conduct electricity. The SI unit of conductivity is siemens per meter $(S/m)$

Which expression has the same SI base units as pressure?

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

  1. $\dfrac{force}{length\times speed}$

  2. $\dfrac{force}{length\times time}$

  3. $\dfrac{mass}{length\times (time)^2}$

  4. $\dfrac{mass\times (time)^2}{length}$

Show answer
Correct Option: C
Explanation:
Pressure is force per unit area.
$P = \dfrac FA=\dfrac {MLT^{-2}}{L^2}=\dfrac M{LT^2}$