Tag: fundamental quantities

Questions Related to fundamental quantities

In International System of units, there are seven base quantities whose units are defined. Which physical quantity has a prefix with its unit?

physics measurements and units summary of si units fundamental quantities system of units

  1. Mass

  2. Thermodynamic temperature

  3. Luminous intensity

  4. Amount of substance

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Correct Option: A
Explanation:

Unit of mass is kilogram and here, kilo is a prefix used in the unit. Thus mass is the physical quantity which has prefix with its unit.

The Richardson equation is given by $I = AT^2 e^{-B/kT}$. The dimensional formula for $AB^2$ is same as that for

physics measurements and units summary of si units fundamental quantities system of units

  1. $IT^2$

  2. $kT$

  3. $Ik^2$

  4. $Ik^2/ T$

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Correct Option: C
Explanation:

$I = AT^2 e^{-B/kT}$
Dimensionally, $A = I/T^2$, dimensions of B = kT
($\because$ power of exponential is a number)
$\displaystyle AB^2 = \frac{I}{T^2} (kT)^2 = Ik^2$

The SI unit of temperature is Kelvin.

physics measurements and units summary of si units fundamental quantities system of units

  1. True

  2. False

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Correct Option: A
Explanation:
S.I. unit of temperature is Kelvin represented by $K$.
Hence the above statement is true.

S.I. unit of frequency is _______.

physics measurements and units summary of si units fundamental quantities system of units

  1. Hertz

  2. Candela

  3. Newton

  4. Dyne

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Correct Option: A
Explanation:
Frequency is defined as the number of revolutions completed by the object in one second.
S.I. unit of frequency is Hertz denoted by $Hz$.

The density of silver is _______ times greater than that of water.

physics measurements and units summary of si units fundamental quantities system of units

  1. 14

  2. 10.4

  3. 12

  4. None of these

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Correct Option: B
Explanation:
Density of silver is   $10.49 \ g/cm^3$ and that of water is $1 \ g/cm^3$.
Density is silver is $10.49$ times than that of water. Thus the given statement is false.

Unit of relative density is kg m$^{-3}$

physics measurements and units summary of si units fundamental quantities system of units

  1. True

  2. False

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Correct Option: B
Explanation:

Relative density is a unitless quantity. Thus the given statement is false.

The SI unit of pressure is ______.

physics measurements and units summary of si units fundamental quantities system of units

  1. $N/{m^2}$

  2. Pa

  3. Both A and B

  4. None of the above

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Correct Option: C
Explanation:
As pressure $=\dfrac {Force (N)}{Area (m^2)}=N/m^2$
Its $SI$ unit is $N/m^2$ or Pa (passed)
option $-c$ is correct

Force F  and density d are related as F is equal to A divided by B plus root d obtain dimensions of A

physics measurements and units summary of si units fundamental quantities system of units

  1. $M^ \dfrac{3}{2} L ^ {\dfrac{-1}{2} }T^{-2}$

  2. $M^ \dfrac{3}{2} L ^ {\dfrac{-1}{2} }T ^ {2}$

  3. $M^ \dfrac{3}{2} L ^ {\dfrac{1}{2} }T ^ {2}$

  4. $M^ \dfrac{3}{2} L ^ {\dfrac{5}{2} }T ^ {-2}$

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Correct Option: A

Illuminance of a surface is measured in

physics measurements and units summary of si units fundamental quantities system of units

  1. lumen

  2. candela

  3. lux

  4. lux $m^{-2}$

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Correct Option: C
Explanation:

Illuminance is luminous flux per unit area, it is measure in 'lux'.

Dyne-sec is the unit of

physics measurements and units summary of si units fundamental quantities system of units

  1. momentum

  2. force

  3. work

  4. angular momentum

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Correct Option: A
Explanation:

Change in momentum $=Force \times time=dyne-sec$