Physics · Science General

Units and Measurement

1,044 Questions

Master the fundamentals of physics with these practice questions on units and measurement. The topics include fundamental SI units, derived quantities, and specific units for power, force, and light. These questions are essential for building a strong foundation for competitive exams.

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Units and Measurement Questions

Multiple choice physics measurements and experimentation vernier calliper and screw gauge least count of vernier calliper and screw gauge measurement of length

The length  and width of a rectangular room are measured to be $3.95 \pm  0.05 m$ and $3.05 \pm  0.05m$, respectively. The area of the floor is 

  1. $12.05\pm 0.01m^2$
  2. $12.05\pm 0.005m^2$
  3. $12.05\pm 0.34 m^2$
  4. $12.05\pm 0.40m^2$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Length of the room  $l = 3.95 \pm 0.05 \ m$
Width of the room  $b = 3.05\pm 0.05 \ m$
Absolute area of the room  $A = lb = 3.95\times 3.05 = 12.05 \ m^2$
Error in area of room   $\dfrac{\Delta A}{A} = \dfrac{\Delta l}{l}+\dfrac{\Delta b}{b}$
$\therefore$   $\dfrac{\Delta A}{12.05} = \dfrac{0.05}{3.95}+\dfrac{0.05}{3.05}$
$\implies \ \Delta A = 0.34 \ m^2$
Thus area of the room is written as  $12.05\pm 0.34 \ m^2$ 

Multiple choice physics units and measurement: error analysis rounding off digits rounding of digits standard form

Calculate area enclosed by a circle of diameter $1.06\ m$ to correct number of significant figures.

  1. $ 0.883 m^2$
  2. $ 0.0883 m^2$
  3. $ 0.88333 m^2$
  4. $ 0.8830 m^2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Area = $ \pi (\dfrac{d}{2})^2  $

$ \Rightarrow Area = \dfrac{22}{7}\times 0.53^2 = 0.882828 $
But, no of significant in diameter should be equal to the no. of significant in Area, so Ans is $ 0.883 m^2$

Multiple choice mutual inductance electromagnetic induction electromagnetic induction and alternating currents physics

Give the MKS units for the following quantities.
Magnetic Induction.

  1. Weber$/m^3$.
  2. Weber$/m^2$.
  3. Weber$/m^4$.
  4. Weber$/m^5$.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

B. $Weber/m^2$

The term magnetic flux density refers to the fact that B is magnetic flux per unit surface. This relationship is based on Faraday's law of magnetic induction.
The SI unit measuring the strength of B is T(Tesla= $Weber/m^2$)

Multiple choice

The SI unit of pressure is the?

  1. Bernoulli

  2. Pascal

  3. Boyle

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

The Pascal (Pa) is the SI unit for pressure, defined as one Newton per square meter.

Multiple choice physics dynamics - explaining motion physical quantities motion and measurement units - definitions and systems

In particular system of unit, if the unit of mass becomes twice and that of time becomes half, then $8$ Joules will be written as _______ units of work

  1. $16$
  2. $1$
  3. $4$
  4. $64$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
The unit of work is $kg\ m^2/s^2$.

$8Joule=\dfrac { 8M{ L }^{ 2 } }{ { T }^{ 2 } }$

$ =\dfrac { 8(1kg){ (1m) }^{ 2 } }{ { (1s) }^{ 2 } } $

On doubling the unit of mass and unit of time is halved:
$=\cfrac { 8(2\quad unit\quad of\quad mass){ (1m) }^{ 2 } }{ { \left( \frac { 1 }{ 2 } unit\quad of\quad time \right)  }^{ 2 } }$

$ =\dfrac { 8\times 2 }{ { \left( \frac { 1 }{ 2 }  \right)  }^{ 2 } } units\quad of\quad work\\ =64\ units\quad of\quad work.$

Multiple choice physics units and measurement: error analysis significant figures significant figures and rounding of digits units and measurements

The length and breadth of a rectangular sheet are 16.2 cm and 10.1 cm, respectively. The area of the sheet in appropriate significant figures and error is:

  1. $164 \pm 3 cm^2$
  2. $163.62 \pm 2.6 cm^2$
  3. $163.6 \pm 2.6 cm^2$
  4. $163.62 \pm 3 cm^2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let the length and breadth of a rectangular sheet are measured by using a meter scale as 16.2 cm and 10.1 cm respectively. Each measurement has three significant figures.
$\therefore$ Length l can be written as
$l = 16.2 \pm 0.1 cm = 16.2 cm \pm 0.6$%

Similarly, the breadth b can be written as
$b = 10.1 \pm 0.1 cm = 10.1 cm \pm 1$%

Area of the sheet,
$A = l \times b = 163.62 cm^2 \pm 1.6% =163.62 \pm 2.6 cm^2$
Therefore, as per rule, the area will have only three significant figures and errors will have only one significant figure.
Rounding off, we get $A = 164 \pm 3 cm^2$

Multiple choice physics units and measurement: error analysis significant figures significant figures and rounding of digits units and measurements

Write down the significant figures in the following
1. $5238$ N
2. $4200 $kg

  1. $4 , 4$
  2. $4 , 2$
  3. $4, 3$
  4. $5, 3$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
All non-zero digits are significant and last zeros are not considered as significant.
(a) : The given number $5238$ has four significant figures.
(b) : The given number $4200$ has two significant figures.
Multiple choice physics units and measurement: error analysis significant figures significant figures and rounding of digits units and measurements

Find the value of following on the basis of significant figure rule:
The height of a man is $5.87532$ ft. But measurement is correct upto three significant figures. The correct height is?

  1. $5.86$ ft
  2. $5.87$ ft
  3. $5.88$ ft
  4. $5.80$ ft
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Significant figures upto three significant figures for the given question is 5.875 . Therefore, 5 is equal to 5 and we can round off the digit preceding 5 is increased by 1.


Therefore , now the correct answer vis 5.88 ft.
Therefore answer  c is correct.

Multiple choice physics gravitational fields representing a gravitational field gravitational field circular motion and gravitation

Which of the following represents the unit for gravitational intensity?

  1. N
  2. $kgm^{-2}$
  3. $Nkg^{-1}$
  4. $ms^{-3}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Gravitational intensity is nothing but the acceleration due to gravity $=g=F _g/m$


Now we know that the SI unit of $F _g$ is $Newton(N) $ and that of $m$ is $kg$
So SI unit of $g=N/kg=Nkg^{-1}$ or $m/s^2$ 

Hence correct answer is option $C $