Tag: measurements and units

Questions Related to measurements and units

A physical quantity u is given by the relation $u=\dfrac{B^2}{2\mu _0}$
Here, $B=$ magnetic field strength
$\mu _o=$ magnetic permeability of vacuum
The name of physical quantity u is?

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

  1. Energy

  2. Energy density

  3. Pressure

  4. None of these

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Correct Option: B

Match the columns :

I II
1. Mass a. $m/s^2$
2. Weight b. kilogram
3. Gravitational acceleration c. $Nm^2\,\,kg^{-2}$
4. Gravitational constant d. Newton 

 

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

  1. 1-a ,2-b ,3-c ,4-d

  2. 1-b ,2-a ,3-d ,4-c

  3. 1-b ,2-d ,3-c ,4-a

  4. 1-b ,2-d ,3-a ,4-c

Show answer
Correct Option: D
Explanation:

Answer is D.

The right matches are given below.

1. Mass                                   -  b. kilogramII. same everywhere
2. Weight                                -  d. Newton IV. depends on the altitude
3. Gravitational acceleration  -  a. $m/s^2$I. zero at the center
4. Gravitational constant        -  c. $Nm^2\,\,kg^{-2}$III. remain constant in the universe

The SI units of mass and weight are ______

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

  1. kg and kg

  2. N and kg

  3. kg and N

  4. N and N

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Correct Option: C
Explanation:

Mass is intrinsic nature of any object or material and it doesn't vary or depend on gravitational field around it.
Weight is the force experienced by an object and it depends on both the mass as well as gravitational field which it experiences in a particular place.

Name the physical quantities related to the following units km$^2$

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

  1. Mass

  2. Volume

  3. Length

  4. Area

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Correct Option: D
Explanation:

Every unit of length has a corresponding unit of area, namely the area of a square with the given side length. Thus areas can be measured in square kilometres, or ${ km }^ { 2 }$.

How watt is related to the fundamental units?

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

  1. kg m$^2 s^{-3}$

  2. kg m$^2 s^{-2}$

  3. Nm $s^{-1}$

  4. Nm

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Correct Option: A
Explanation:

SI unit of mass is Kg , acceleration is $ms^{-2}$ ad of velocity is $ms^{-1}$.

Now power is defined as $=$ force $\times  $ velocity, where $F=m\times a$
So, $P=m\times a\times v$ , putting the SI unit of $m, a, v$
We get SI unit of power is $kgm^2s^{-3}$.

Which pair of following quantities has dimensions different from each other. 

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

  1. Impulse and linear momentum

  2. Planck's constant and angular momentum

  3. Moment of inertia and moment to force

  4. Young's modulus and pressure

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Correct Option: C
Explanation:

Moment of inertia $=\dfrac { 1 }{ 2 } \times mass\times { \left( Radius\quad of\quad gyration \right)  }^{ 2 }= \left[ { M }^{ 1 }{ L }^{ 2 }{ T }^{ 0 } \right] $


Moment of force $=$ torque $= N.m = $$\left[ { M }^{ 1 }{ L }^{ 2 }{ T }^{ -2 } \right] $

Both are different from each other.

$\displaystyle { g\ cm\ s }^{ -2 }$ is also known as 

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

  1. newton

  2. erg

  3. pascal

  4. dyne

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Correct Option: D
Explanation:

CGS unit of force is dyne.

$F=mg$, CGS unit of mass is gram  and gravity is $cm/s^2$ 
So, unit of dyne is $gcms^{-2}$.

In the SI system, the unit of P.E. is

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

  1. Erg

  2. Dyne-cm

  3. J

  4. Watt

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Correct Option: C
Explanation:

SI unit of potential energy is Joule $(J)$.

Identify the uncommon quantity

Weight, spring balance, newton, kilogram 

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

  1. kilogram

  2. Weight

  3. spring balance

  4. newton

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Correct Option: A
Explanation:

The spring balance is the device used for measurement of weight. The weight of a body is measured in terms of the newton. On the other hand, kilogram is the unit for the mass of the body.


Therefore, spring balance, weight and Newton are related to the same thing i.e.the weight of a body whereas the kilogram is related to the mass of the body. So, kilogram is different.

Identify the common unit used to measure energy?

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

  1. Newtons

  2. Joules

  3. Grams

  4. Meters

  5. Liters

Show answer
Correct Option: B
Explanation:

Newton is the unit of force.

Joules is the SI unit of energy. It is equivalent to newton-meter($N-m$).
Grams is a unit of mass.
Meter is the SI unit of distance.
A liter is a unit of volume and equivalent to $dm^3$.

Therefore option $B$ is correct.