Tag: kinds of units

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

The energy which an electron acquires when accelerated, through a potential difference of $1$ volt is called

  1. $1$ Joule
  2. $1$ eV
  3. $1$ erg
  4. $1$ watt
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The energy which an electron acquires when accelerated, through a potential difference of 11 volt is called 1 eV. It is a unit of energy.  It is usually used as a measure of particle energies although it is not an SI (System International) unit. The SI unit for energy is the Joule. $1\,eV=1.602\times 10^{-19}\,Joules$

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

The Sl unit of length is the meter. Suppose we adopt a new unit of length which equals to $x$ meters. The area 1 $m ^ { 2 }$ expressed in terms of the new unit has a magnitude:

  1. $x$
  2. $x ^ { 2 }$
  3. $\dfrac { 1 } { x }$
  4. $\dfrac { 1 } { x ^ { 2 } }$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

SI unit of Length $=$ meters.

New Unit of Length $=x$ meters.

$1m=\dfrac 1x$ new units

SI unit of area : 

$A= 1m^2$   

$=1\times 1m^2$                        

$=\dfrac 1x\times \dfrac 1x $     

$=\dfrac{1}{x^2}$     

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

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

  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 $\dfrac {m\sqrt {gl}}{2\sqrt {3}}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice physics measurements and units kinds of units fundamental quantities standardized measurement

If $10 ^ { 7 }$ era is taken as unit of energy, $10 ^ { 5 }$ dyne as the unit of force, one second as unit of time. what is, the unit of length?

  1. $1$ $m$
  2. $10$ $m$
  3. $100$ $m$

  4. None
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Energy E = M L^2 T^-2 = 10^7 erg = 1 Joule. Force F = M L T^-2 = 10^5 dyne = 1 Newton. Time T = 1 second. Using F = M L T^-2 and E = F L, we get 1 Joule = 1 Newton * L, so L = 1 meter.

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

The MKS unit of quantity $\dfrac{\pi \eta r^4}{2}$ is :

  1. $N s {m}^{2} radian $
  2. $Ns/m/Radian$
  3. $Radian/Ns/m$
  4. $ Ns/m/Radian^2 $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Unit of $\pi $ is radians.

Unit of $r$ is $m$.
Unit of coefficient of viscosity, $\eta =N\, s\, { m }^{ -2 } $
Whereas $2$ is just a number, so it is unit less.
Therefore, Unit of given expression $=radian \times$ $N\, s\, { m }^{ -2 }\times { m }^{ 4 }=N\,s \, { m }^{ 2 } \ radian$