Tag: fundamental and derived quantities

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Multiple choice physics measurements and units some examples of derived units fundamental and derived quantities fundamental and derived units

The unit of power is:

  1. $Kilowatt$
  2. $kWhv$
  3. $dyne$
  4. $joule$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Power is defined as the work done per unit time. So to get the SI unit of power :

$Power=\dfrac{Work}{Time}$

SI unit of Work $=$ Joules

SI unit of Time $=$ second

So S.I. unit of power $=\dfrac{Joule}{Second}=Watt$

$1000\,Watt=1\,Kilowatt$

Multiple choice physics measurements and units some examples of derived units fundamental and derived quantities fundamental and derived units

The velocity of a particle is given as $v = a + b t + c t ^ { 2 }$ .the velocity is measured in $\mathrm { ms } ^ { - 1 }$ , then units of a and c are

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

The magnitudes of physical quantities can be added together or subtracted from one another only if they have the same dimensions. 

$[a]=[u]=ms^{-1}$

$[ct^2]=[v]=ms^{-1}$

$[c]=[\dfrac{v}{s^2}]=ms^{-1-2}$

$[c]=ms^{-3}$
Option A

Multiple choice physics measurements and units some examples of derived units fundamental and derived quantities fundamental and derived units

Three of these quantities have the same unit. Which quantity has a different unit ?

  1. $\dfrac{distance}{energy}$
  2. $force$
  3. $power\times time$

  4. rate of change of momentum
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Force, power times time (energy), and rate of change of momentum (force) all have units of Newtons or Joules. Distance/energy has units of m/J, which is different from the others.

Multiple choice physics measurements and units some examples of derived units fundamental and derived quantities fundamental and derived units

Pascal is a unit of 

  1. Pressure

  2. Force

  3. Linear momentum

  4. Energy
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The pascal $(Pa)$ is the SI derived unit of pressure used to quantify internal pressure, stress, Young's modulus and ultimate tensile strength. The unit, named after Blaise Pascal, is defined as one newton per square metre.

Multiple choice physics measurements and units some examples of derived units fundamental and derived quantities fundamental and derived units

Curie is the unit of 

  1. decay constant

  2. radio-activity

  3. half-life

  4. average life
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

We measure the intensity of radioactive emission by  number of atoms that get transformed to new atoms per unit time. 
Curie(Ci) is the standard unit used for measuring radio-activity.
Curie is defined as the emission rate of 1g of radium which is equal to $3.7 \times 10^{10}$ transformations per second.

Multiple choice physics measurements and units some examples of derived units fundamental and derived quantities fundamental and derived units

The magnetic moment of electron is :

  1. $ 9.27\times 10^{-24} $ Joule/Tesla
  2. $ 9.27\times 10^{-24} $ Tesla/Joule
  3. $ 9.27\times 10^{-23} $ Joule/Tesla
  4. $ 9.27\times 10^{-23} $ Tesla/Joule
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Electrons spinning on their axes are magnetic dipoles that may or may not cancel out each other depending on the type of dipole.
We measure the  magnetic moment of electron in Joule / Tesla.
The value of magnetic dipole of an electron is $9.27 \times 10^{-24}$ Joule/Tesla.