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

The SI unit of electron mobility is  :

  1. ${M^2}{S^{ - 1}}V - 1$

  2. <span>$=m^2 s^{-1}V^{-1}$</span>

  3. $m{s^{ - 1}}V$

  4. ${m^2}{s^{ - 2}}V$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Electron mobility:- It is the ratio of velocity to electric field.

$\mu=\dfrac{v _e}{E}$. . . . . . .(1)
SI unit of velocity, $v _e$ $=m/s$
SI unit of electric field, $E$ $=V/m$
From equation (1),
SI unit of electron mobility is $=\dfrac{m/s}{V/m}$
$=m^2/Vs$
$=m^2 s^{-1}V^{-1}$

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

The dimensional formula of a physical quantity is $\displaystyle { M }^{ 1 }{ L }^{ 2 }{ T }^{ 3 }{ I }^{ -1 }$ .What is its SI unit?

  1. $\displaystyle { kg\quad m }^{ 2 }{ s }^{ 3 }{ A }^{ -1 }$

  2. $\displaystyle { kg\quad m }^{ 2 }{ s }^{ 2 }{ A }$

  3. $\displaystyle { kg\quad ms }^{ -3 }{ A }^{ 2 }$

  4. $\displaystyle { kg}^{2}{ m }^{ 2 }{ s }^{ 3}{ A }^{ -1 }$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

SI unit of $M$ is $kg$, that of $L$ is $m$, $T$ is $s$ and $I$ is $A$.
So, SI unit of $[M^1L^2T^{3}I^{-1}]$ is  $kg \ m^2s^{3}A^{-1}$.

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

Find the unit of the following derived quantities: 
(a) Force [Hint: Force = Mass $\times$ acceleration]
(b) Pressure $\left[Hint: Pressure =\frac{force}{Area}\right]$

  1. <span>$kg\,m\,s^{-2}$ and&nbsp;</span>$kg\,m^{-1}\,s^{-2}$

  2. $kg\,m\,s^{-1}$ and $Kg\,m^{-2}\,s^{-1}$

  3. <span>&nbsp;</span>$ N$&nbsp;and&nbsp;$ Pa$

  4. None of these
Reveal answer Fill a bubble to check yourself
A,C Correct answer
Explanation
Force   $F = ma$
So, unit of force is  $kg \ m/s^2$
Newton $(N)$ is also the unit of force.
Pressure   $P = \dfrac{F}{A}$
Unit of pressure   $ = \dfrac{kg \ m/s^2}{m^2} = kg \ m^{-1}s^{-2}$
Also, pressure is measured in Pascal $(Pa)$.
Multiple choice physics turning effects of forces the turning effect of a force moment of force or torque couple

A disc is rolling on a surface without slipping. What is the ratio of its translational to rotational kinetic energies?

  1. $5:2$

  2. $2:1$

  3. $3:2$

  4. $2:3$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Translational Kinetic Energy$=\cfrac{1}{2}mv^{2}=KE _{T}$
Rotational KE$=\cfrac{1}{2}I\omega^{2}$
$v=r\omega\,\,\,\,,I=\cfrac{1}{2}MR^{2}$
Rotational KE$=\cfrac{1}{2}\times\cfrac{1}{2}mR^{2}\times(\cfrac{v}{R})^{2}$
$KE _{r}=\cfrac{1}{4}mv^{2}$
$\cfrac{KE _{T}}{KE _{r}}=\cfrac{\cfrac{1}{2}mv^{2}}{\cfrac{1}{4}mv^{2}}=2:1$
Multiple choice physics medical imaging ultrasonic sound using ultrasound in medicine ultrasound and its applications

The properties of ultrasound that make it useful is/are 

  1. high power and high speed.

  2. high power and good directivity.

  3. high frequency and high speed.

  4. high frequency and bending around the objects.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Answer is B.
The ultrasonic devices achieve high directivity by modulating audible sound onto high frequency ultrasound. The higher frequency sound waves have a shorter wavelength and thus don't spread out as rapidly. For this reason, the resulting directivity of these devices is far higher than physically possible with any loudspeaker system. However, they are reported to have limited low-frequency reproduction abilities. 
High power ultrasound can break up stony deposits or tissue, accelerate the effect of drugs in a targeted area, assist in the measurement of the elastic properties of tissue, and can be used to sort cells or small particles for research.
Hence, the above characteristics make ultrasound to be very useful.