Tag: measurement of physical quantities

Questions Related to measurement of physical quantities

Which system of units has been taken as standard?

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. M.K.S

  2. C.G.S

  3. Both

  4. None

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Correct Option: A
Explanation:

In S.I system (standard international system), the units of mass,length and time are same,as that of M.K.S system. However , it is an enlarged system encompassing all fundamental units.

MKS system means

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. Millimeter, kilometre, seconds

  2. Metre, kilogram, seconds

  3. Millisecond, kilolitre, seconds

  4. Milligram, kilogram, seconds

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Correct Option: B
Explanation:

In MKS system,M stands for metre (length),K stands for kilogram(mass) and S stands for seconds(time).

Units of Planck's constant in CGS system are:

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. Erg per second

  2. Second per erg

  3. Erg second

  4. Erg per second per second

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Correct Option: C
Explanation:

Planck's constant, symbolized h, relates the energy in one quantum (photon) of electromagnetic radiation to the frequency of that radiation.  In the centimeter-gram-second (CGS) or small-unit metric system, it is equal to approximately $6.626176\times 10^{-27}\,$Erg Second.

If force (F), work (W) and velocity (V) are taken as fundamental quantities then the dimensional formula of time (T) is

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. $\left[ { W }^{ 1 }{ F }^{ 1 }{ V }^{ 1 } \right] $

  2. $\left[ { W }^{ 1 }{ F }^{ 1 }{ V }^{ -1 } \right] $

  3. $\left[ { W }^{ -1 }{ F }^{ -1 }{ V }^{ -1 } \right] $

  4. $\left[ { W }^{ 1 }{ F }^{ -1 }{ V }^{ -1 } \right] $

Show answer
Correct Option: D
Explanation:
We know,

$[W]=ML^2T^{-2}$

$[F]=MLT^{-2}$

$[V]=LT^{-1}$

Let,
$W^aF^bV^c=M^0L^0T$

$a+b=0$

$2a+b+c=0$, $a+c=0$

$-2a-2b-c=1$

$c=-1,a=1,b=-1$

Hence , $[T]=[WF^{-1}V^{-1}]$

Option $\textbf D$ is the correct answer

The ratio of SI unit to CGS unit of G is

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. $10^{3}$

  2. $10^{2}$

  3. $10^{-2}$

  4. $10^{-3}$

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Correct Option: A
Explanation:
SI unit of G is  $\dfrac{N m^2}{kg^2}$.
CGS unit of G is  $\dfrac{dyne \ cm^2}{gm^2}$
We know that  $1 \ N = 10^5 \ dyne$ and $1 \ m = 10^2 \ cm$ and $1 \ kg = 10^3 \ gm$
So ratio of SI unit to CGS unit   $ = \dfrac{\dfrac{N  \ m^2}{kg^2}}{\dfrac{dyne \ cm^2}{gm^2}} = \dfrac{\dfrac{10^5 \ dyne \ (10^2 \ cm)^2}{(10^3 \ gm)^2}}{\dfrac{dyne \ cm^2}{gm^2}} = 10^3$
Correct answer is option A.

Which of the following represents the magnitude of a temperature correctly?

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. 10 k

  2. 10 Kelvins

  3. 10 Ks

  4. 10 K

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Correct Option: D
Explanation:
Temperature is measured in Kelvin which is represented by $K$
Thus, $10 \ K$ is the correct representation of temperature.

1 Newton $=$

standardized measurement measurement of physical quantities need of unit for measurement measurements and experimentation physics

  1. $10^4 dyne$

  2. $10^5 dyne$

  3. $10^6dyne$

  4. $10^7 dyne$

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Correct Option: B
Explanation:
S.I. unit of force is Newton and CGS unit of force is done.

We know $F=ma$
so, force can be expresses in S.I. Units as $Kg m s^{-2}$
and dyne can be expressed as $gcms^{-2}$
1 Newton= $kg ms^{-2}$ 
                 =$10^3 g*10^2 cms  s^{-2}$
                 =$10^5 g cm s^{-2}$
                 =$10^5 dyne$

How many fundamental units are present in the SI system of units?

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

  1. 5

  2. 6

  3. 7

  4. 3

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Correct Option: C
Explanation:

There are seven fundamental units in the SI system of units which are mass, length, time, temperature, electric current, mole and luminous intensity.

State whether true or false.
The quantity of matter in a body is called its mass.

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 a body.

The units which can neither derived from one another nor resolved into any thing more basic are called 

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

  1. Fundamental unit

  2. Scale

  3. Derived unit

  4. Standard unit

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Correct Option: A
Explanation:

The units which can neither derived from one another nor resolved into any thing more basic are called fundamental unit. It is independent of any other unit.