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Measurement of physical quantities - class-VII

Description: measurement of physical quantities
Number of Questions: 23
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Tags: measurement of physical quantities physics measurements and experimentation
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Which of the following does not has fundamental unit?

  1. Mass

  2. Time

  3. Force

  4. length


Correct Option: C
Explanation:

The fundamental units are the units of the fundamental quantities, as defined by the International System of Units. They are not dependent upon any other units, and all other units are derived from them. There are seven basic fundamental quantities: Length, mass, time, electric current, amount of substance, luminous intensity & temperature. The quantities which are derived with the help of these basic physical quantities are called derived quantities. They are density, volume, pressure, force, etc.

The wavelength of light is usually expressed in

  1. Micron

  2. Fermi

  3. Nanometer

  4. Angstrom


Correct Option: D
Explanation:

Angstrom $(\dot A)$ unit of length used chiefly in measuring wavelengths of light, equal to $10^{-10}$ metre, or $0.1$ nanometer.  It is used to express wavelengths of visible light, ultraviolet (UV) light, X rays, and gamma rays.

Which of the following is the largest unit of length?

  1. Light year

  2. Astronomical unit

  3. Parsec

  4. Nothing can be decided


Correct Option: C
Explanation:

Parsec is the largest unit of length. It is usaed to measure the space distances.


$1\,Parsec=3.26$ light year

In a tug-of-war between the teams A and B, the rope breaks at a point which is nearer to A. Then

  1. A has applied more force

  2. B has applied more force

  3. A and B both have applied same force

  4. Neither has applied any force


Correct Option: C

The gravitational unit of force in the metric system is

  1. g wt

  2. N

  3. kg wt

  4. None of these


Correct Option: C
Explanation:

Gravitational force is the force exerted by earth on any body which attracts to body towards earth. It is same as any other force.  The gravitational unit of force in the metric system is $kg\,wt$.

The amount of energy emitted per unit time is called _______ .

  1. Solar luminosity

  2. Luminous intensity

  3. Luminous flux

  4. Solar intensity


Correct Option: A

The unit of power is

  1. Joule per second only

  2. Joule only

  3. Joule per second and watt both

  4. Watt only

  5. Erg


Correct Option: C
Explanation:

Power is defined as work divided by time, so its units are joules/second. Scientists have another name for this unit, too. It's the watt, named after James Watt, the Scottish inventor who helped develop the steam engine that powered the Industrial Revolution. In the SI system, the watt is defined as:


$1\,watt=1\,J/s=1\,kg\,m^2/s^3$

The correct relation is -

  1. Density = Mass $ \displaystyle \times $ Volume

  2. Mass = Density $ \displaystyle \times $ Volume

  3. Volume = Density $ \displaystyle \times $ Mass

  4. Density = Volume $ \displaystyle \div $ Mass


Correct Option: B
Explanation:

We know that Density = Mass / Volume

So, Mass = Density X Volume (Option B)

Weight of a body is measured by a 

  1. Beam balance

  2. Physical balance

  3. Spring balance

  4. Density bottle


Correct Option: C
Explanation:

Weight is measured with the help of Spring Balance. (Option C) 

The SI unit of weight is

  1. Kgf

  2. Gf

  3. N

  4. None of these


Correct Option: C
Explanation:

The SI unit of weight is Newton  (N). Option C

Which one of the following is not a unit of British system of units?

  1. Foot

  2. Metre

  3. Pound

  4. Second


Correct Option: B
Explanation:

Among the given units metre is not a unit of British system whereas all other units belong to this system.

The dimensions of the quantities in one (or more) of the following pairs are the same. Identify the pair(s).

  1. Torque and work

  2. Angular momentum and work

  3. Energy and Young's modulus

  4. Light year and wavelength


Correct Option: A,D
Explanation:

Torque$={ M }^{ 1 }{ L }^{ 2 }{ T }^{ -2 }$

Work$={ M }^{ 1 }{ L }^{ 2 }{ T }^{ -2 }$
angular momentum(L)=${ M }^{ 1 }{ L }^{ 2 }{ T }^{ -1 }$
Energy$={ M }^{ 1 }{ L }^{ 2 }{ T }^{ -2 }$
Young's Modulus $(Y)$$={ M }^{ 1 }{ L }^{ 2 }{ T }^{ -2 }$
Light year$=L$
Wavelength$=L$

1 Me V$=$

  1. $1.6\times 10^{-12} Joules$

  2. $1.6\times 10^{-10} Joules$

  3. $1.6\times 10^{-13} Joules$

  4. $1.6\times 10^{-11} Joules$


Correct Option: A

As compared to cumulative average-time learning model, learning model which predicts more cumulative total time to produce more units is known as ____________.

  1. incremental unit time learning model

  2. incremental price learning model

  3. incremental unit average model

  4. incremental cost learning model


Correct Option: A

The unit of universal gas constant is

  1. ${Dymes}/{C}$

  2. $Ergs$ ${cm}/{mole} K$

  3. ${Watt}/{K}$

  4. ${Joule}/{mole} K$


Correct Option: D
Explanation:

Gas equation,
$PV=nRT$

$R=\dfrac{PV}{nT}$

$[R]=\left[ \dfrac{PV}{nT}\right]$

$[R]=\dfrac{Joule}{mole \ K}$

Option D

The SI unit of amplitude of oscillation is

  1. cm

  2. m

  3. km

  4. none of these


Correct Option: B
Explanation:

SI unit of amplitude of oscillation is metre  $(m)$

The wavelength of light is expressed in

  1. Metre

  2. Micron

  3. Light year

  4. Angstrom


Correct Option: D
Explanation:

Angstrom $(\dot A)$ unit of length used chiefly in measuring wavelengths of light, equal to $10^{-10}$ metre, or $0.1$ nanometer.  It is used to express wavelengths of visible light, ultraviolet (UV) light, X rays, and gamma rays.

State whether given statement is True or False.
The SI unit of mass is milligram.

  1. True

  2. False


Correct Option: B
Explanation:

SI unit of mass is kilogram i.e.  $Kg$.
Thus the above statement is false.

If the displacement, velocity and acceleration of a particle at time t be x, v and f respectively, then which one is true?

  1. $f=v^3\dfrac{d^2t}{dx^2}$

  2. $f=-v^3\dfrac{d^2t}{dx^2}$

  3. $f=v^2\dfrac{d^2t}{dx^2}$

  4. $f=-v^2\dfrac{d^2t}{dx^2}$


Correct Option: B
Explanation:

We know that the velocity can be written as:
$v=\dfrac{dx}{dt}$

Therefore, $\dfrac1v=\dfrac{dt}{dx}$

Now, expressing $f$ in terms of velocity.

$\dfrac{d^2t}{dx^2}=\dfrac{d\begin{pmatrix}\dfrac{dt}{dx}\end{pmatrix}}{dx}=\dfrac{d\begin{pmatrix}\frac{1}{v}\end{pmatrix}}{dx}=-\dfrac{1}{v^2}\dfrac{dv}{dt}\times\dfrac{1}{v}$
$\Rightarrow\;f=-v^3\dfrac{d^2t}{dx^2}$


A __________ unit does not change with respect to space and time.

  1. derived

  2. standard

  3. regular

  4. large


Correct Option: B
Explanation:

A unit is said to be a standard unit of does not change with respect to space and time.

Which of the following pairs has not the same dimension?

  1. Stress; pressure

  2. Force; surface tension

  3. Impulse; linear momentum

  4. Frequency; angular velocity


Correct Option: B
Explanation:

Surface Tension$ (T) =\dfrac{ Force}{Length}$  . . . . . (1)

Since, $Force = Mass \times Acceleration$

And, $Acceleration = \dfrac{velocity}{ time}= [L T^{-2}]$

$\therefore $ The dimensional formula of force $= M^1L^1T^{-2}$ . . . . (2)

On substituting equation (2) in equation (1) we get,

Surface Tension $(T) = \dfrac{Force}{  Length}$

Or, $T=\dfrac{[M^1L^1T^{-2}]}{[L^{1}]}=M^1T^{-2}$ 

Therefore, surface tension is dimensionally represented as $[M^1T^{-2}]$


Dimension of force $=M^1L^1T^{-2}$

So the dimension of force and surface tension are different.

The force F is given in terms of time t and displacement x by the equation F = A cosBx + C sin Dt. The dimensional formula of D/B is______

  1. $[M^oL^oT^o]$

  2. $[M^oL^o{T}^{-1}]$

  3. $[M^o{L}^{-1}T^o]$

  4. $[M^o{L}^{1} {T}^{-1}]$


Correct Option: D
Explanation:

$F = A\ cosBx + C\ sinDt$

the argument, $\theta $ of cos or sin should be dimensionless.
therefore,
dimension of Bx = $[MLT]$
$[B] [L'] = [MLT]$

$[B] = [M{L}^{0}T]$

Similarly $[D][T'] = [MLT]$

$[D] = [ML{T}^{0}$
dimension of $DB=\dfrac{[ML{T}^{0}]}{[ML^0T]}$
= $[L^1{T}^{-1}]$

Which of the following conversions is correct?

  1. 1 atm = 1.01 x 10$^4$ Pa

  2. 1 mm of Hg = 133 Pa

  3. 1 bar = 10$^7$ Pa

  4. 1 torr = 10$^2$ Pa


Correct Option: B
Explanation:

 The answer is $0.0075006157584566$. We assume you are converting between and pascal. You can view more details on each measurement unit: mm Hg or pascal The SI derived unit for pressure is the pascal. $1 mm Hg =133.322387415 \ pascal$.

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