Tag: measurement of physical quantities

Questions Related to measurement of physical quantities

The impulse $J$ required to bring it to rest when it reaches the vertical position.

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

  1. Impulse of $m\sqrt {\dfrac {gl}{3}}$ when it is applied horizontally at distance $l$ from pivoted point

  2. Impulse of $m\sqrt {\dfrac {gl}{3}}$ when it is applied horizontally at distance $\dfrac {l}{2}$ from pivoted point

  3. Minimum impulse is $m\sqrt {\dfrac {gl}{2}}$ when it is applied at distance $l$ from pivoted point

  4. If rod is stopped by applying minimum impulse then the is impulse imparted by pivot is $\dfrac {m\sqrt {gl}}{2\sqrt {3}}$

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Correct Option: A

Which of the following is different from others?

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

  1. Speed

  2. Density

  3. Force

  4. Time

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Correct Option: D
Explanation:

Speed, density and force are the derived physical quantities whereas time is the fundamental physical quantity.

Mass is a _________ physical quantity.

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

  1. derived

  2. fundamental

  3. semi-derived

  4. valueless

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Correct Option: B
Explanation:

There are only $7$ fundamental physical quantity out of which mass is a fundamental quantity.

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

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

  1.  identifying their fundamental dimensions

  2. units of measure

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

  4. All of the above 

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Correct Option: D
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.

State whether true or false.
The mass of a body can never be zero.

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

  1. True

  2. False

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Correct Option: A
Explanation:
Mass of a body is defined as the quantity of matter contained in it. Since, all bodies are made up of certain matter. Thus mass of body can never be zero.

Which one of the following is not a fundamental SI unit?

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

  1. Ampere

  2. Candela

  3. Newton

  4. Kelvin

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Correct Option: C
Explanation:

F = ma = kgms-2

SI unit of force is Newton(W)

Hence, newton is a derived unit

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.

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.

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

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