Learn › MH-CET · Physics › Units and Measurements (Std 11)
Units and Measurements (Std 11) — MH-CET Physics MCQs with Solutions
Free MH-CET Physics Units and Measurements (Std 11) MCQs with step-by-step solutions covering SI Units & Fundamental Quantities, Dimensions & Dimensional Formulae, Dimensional Analysis & Applications, Significant Figures & Rounding, Errors in Measurement, Accuracy, Precision & Order of Magnitude. Practise online on Prepizo — no login needed.
▶ Practise Units and Measurements (Std 11) online (free)
Subtopics
Sample questions with solutions
Q1 — SI Units & Fundamental Quantities · easy · theory
The number of fundamental quantities in the SI system is:
A. Three
B. Five
C. Nine
D. Seven ✓ Correct
Solution: They are length, mass, time, electric current, temperature, amount of substance and luminous intensity.
Q2 — SI Units & Fundamental Quantities · easy · theory
The SI base unit of amount of substance is the:
A. Kilogram
B. Candela
C. Mole ✓ Correct
D. Kelvin
Solution: One mole contains as many elementary entities as there are atoms in $12\text{ g}$ of carbon-12.
Q3 — SI Units & Fundamental Quantities · easy · theory
The SI base unit of luminous intensity is the:
A. Candela ✓ Correct
B. Lumen
C. Watt
D. Lux
Solution: Lumen and lux are derived units of luminous flux and illuminance respectively.
Q4 — SI Units & Fundamental Quantities · easy · theory
The SI base unit of thermodynamic temperature is the:
A. Degree Fahrenheit
B. Degree Celsius
C. Kelvin ✓ Correct
D. Joule
Solution: The kelvin is an absolute scale with its zero at absolute zero.
Q5 — SI Units & Fundamental Quantities · easy · theory
A derived unit is one that:
A. Has no dimensions
B. Is expressed as a combination of fundamental units ✓ Correct
C. Cannot be expressed in terms of other units
D. Is used only in astronomy
Solution: The newton, for example, is $\text{kg}\cdot\text{m}\cdot\text{s}^{-2}$.
Q6 — SI Units & Fundamental Quantities · easy · theory
The SI base unit of electric current is the:
A. Ampere ✓ Correct
B. Ohm
C. Coulomb
D. Volt
Solution: The coulomb is a derived unit, being one ampere second.
Q7 — SI Units & Fundamental Quantities · easy · numerical
The SI unit of force expressed in base units is:
A. $\text{kg}\cdot\text{m}\cdot\text{s}^{-1}$
B. $\text{kg}\cdot\text{m}^{-1}\cdot\text{s}^{-2}$
C. $\text{kg}\cdot\text{m}\cdot\text{s}^{-2}$ ✓ Correct
D. $\text{kg}\cdot\text{m}^2\cdot\text{s}^{-2}$
Solution: From $F = ma$, the newton is $\text{kg}\cdot\text{m}\cdot\text{s}^{-2}$.
Q8 — SI Units & Fundamental Quantities · easy · numerical
One angstrom is equal to:
A. $10^{-6}\text{ m}$
B. $10^{-15}\text{ m}$
C. $10^{-10}\text{ m}$ ✓ Correct
D. $10^{-12}\text{ m}$
Solution: It is a convenient unit for atomic dimensions and for the wavelength of X-rays.
Q9 — SI Units & Fundamental Quantities · easy · numerical
One micron is equal to:
A. $10^{-6}\text{ m}$ ✓ Correct
B. $10^{-3}\text{ m}$
C. $10^{-10}\text{ m}$
D. $10^{-9}\text{ m}$
Solution: It is another name for the micrometre.
Q10 — SI Units & Fundamental Quantities · easy · numerical
A speed of $72\text{ km/h}$ expressed in metre per second is:
A. $36\text{ m/s}$
B. $18\text{ m/s}$
C. $20\text{ m/s}$ ✓ Correct
D. $25\text{ m/s}$
Solution: $72 \times \dfrac{1000}{3600} = 20\text{ m/s}$.
Q11 — Dimensions & Dimensional Formulae · easy · theory
The dimensional formula of a physical quantity expresses:
A. The unit in which the quantity is measured
B. The numerical value of the quantity
C. The accuracy of the measurement
D. How the quantity depends on the fundamental quantities ✓ Correct
Solution: It is written using the symbols $M$, $L$, $T$, $A$, $K$, $\text{mol}$ and $\text{cd}$.
Q12 — Dimensions & Dimensional Formulae · easy · theory
Which of the following is a dimensionless quantity?
A. Force
B. Pressure
C. Momentum
D. Strain ✓ Correct
Solution: Strain is a ratio of two lengths, so the dimensions cancel. Angle and refractive index are likewise dimensionless.
Q13 — Dimensions & Dimensional Formulae · easy · theory
The dimensional formula of force is:
A. $[M^1L^1T^{-2}]$ ✓ Correct
B. $[M^1L^{-1}T^{-2}]$
C. $[M^1L^1T^{-1}]$
D. $[M^1L^2T^{-2}]$
Solution: From $F = ma$: $[M][LT^{-2}] = [M^1L^1T^{-2}]$.
Q14 — Dimensions & Dimensional Formulae · easy · theory
The dimensional formula of work and of energy is:
A. $[M^1L^2T^{-2}]$ ✓ Correct
B. $[M^1L^1T^{-2}]$
C. $[M^1L^2T^{-1}]$
D. $[M^1L^2T^{-3}]$
Solution: Work is force times distance, so $[M^1L^1T^{-2}][L] = [M^1L^2T^{-2}]$.
Q15 — Dimensions & Dimensional Formulae · easy · theory
The dimensional formula of linear momentum is:
A. $[M^1L^2T^{-1}]$
B. $[M^1L^1T^{-1}]$ ✓ Correct
C. $[M^1L^2T^{-2}]$
D. $[M^1L^1T^{-2}]$
Solution: Momentum is mass times velocity.
Q16 — Dimensions & Dimensional Formulae · easy · numerical
The dimensional formula of frequency is:
A. $[M^0L^0T^1]$
B. $[M^0L^0T^{-1}]$ ✓ Correct
C. $[M^1L^0T^{-1}]$
D. $[M^0L^1T^{-1}]$
Solution: Frequency is the number of cycles per second, so only time appears.
Q17 — Dimensional Analysis & Applications · easy · theory
Dimensional analysis can be used to:
A. Find the value of dimensionless constants
B. Determine whether a quantity is a vector
C. Prove that an equation is physically correct
D. Check the correctness of an equation, derive relations and convert units ✓ Correct
Solution: These three uses are its standard applications; the other options are its limitations.
Q18 — Dimensional Analysis & Applications · easy · theory
The principle of homogeneity of dimensions states that:
A. Every term on both sides of a correct equation has the same dimensions ✓ Correct
B. Only fundamental quantities have dimensions
C. Dimensions can be added like numbers
D. All physical quantities have the same dimensions
Solution: Quantities of unlike dimensions can never be added or equated.
Q19 — Dimensional Analysis & Applications · easy · theory
In a dimensionally correct equation, quantities that are added together must have:
A. No dimensions at all
B. Different dimensions
C. The same numerical value
D. The same dimensions ✓ Correct
Solution: This follows directly from the principle of homogeneity.
Q20 — Dimensional Analysis & Applications · easy · numerical
The equation $v = u + at$ is:
A. Dimensionally incorrect
B. Dimensionally correct ✓ Correct
C. Valid only in CGS units
D. Valid only for zero acceleration
Solution: Each term has the dimension $[L^1T^{-1}]$: $[LT^{-2}][T] = [LT^{-1}]$ for the last term.
Q21 — Dimensional Analysis & Applications · easy · numerical
The dimensional formula of the quantity $\dfrac{1}{2}mv^2$ is the same as that of:
A. Momentum
B. Force
C. Work ✓ Correct
D. Power
Solution: Kinetic energy and work share the dimension $[M^1L^2T^{-2}]$.
Q22 — Significant Figures & Rounding · easy · theory
Significant figures in a measurement are:
A. The reliably known digits plus the first uncertain digit ✓ Correct
B. All the digits written down, including leading zeros
C. Only the digits after the decimal point
D. Only the non-zero digits
Solution: They convey the precision with which the measurement was made.
Q23 — Significant Figures & Rounding · easy · theory
Zeros lying between two non-zero digits are:
A. Always significant ✓ Correct
B. Significant only after a decimal point
C. Never significant
D. Significant only in scientific notation
Solution: In $2.0034$, for example, all five digits count.
Q24 — Significant Figures & Rounding · easy · theory
Zeros written to the left of the first non-zero digit are:
A. Always significant
B. Not significant ✓ Correct
C. Significant only if the number is less than one
D. Significant only after a decimal point
Solution: In $0.0025$ the leading zeros merely fix the decimal point, so there are two significant figures.
Q25 — Significant Figures & Rounding · easy · numerical
The number of significant figures in $1.230$ is:
A. $5$
B. $3$
C. $4$ ✓ Correct
D. $2$
Solution: The trailing zero after the decimal point is significant.
Q26 — Significant Figures & Rounding · easy · numerical
The number of significant figures in $2.0034$ is:
A. $2$
B. $4$
C. $3$
D. $5$ ✓ Correct
Solution: The zeros lie between non-zero digits, so all five figures count.
Q27 — Significant Figures & Rounding · easy · numerical
The number of significant figures in $0.0025$ is:
A. $4$
B. $5$
C. $3$
D. $2$ ✓ Correct
Solution: Only $2$ and $5$ are significant; the leading zeros are placeholders.
Q28 — Errors in Measurement · easy · theory
The absolute error in a measurement is defined as:
A. The magnitude of the difference between the measured value and the true value ✓ Correct
B. The error expressed as a percentage
C. The smallest division of the instrument
D. The ratio of the error to the measured value
Solution: It carries the same unit as the quantity being measured.
Q29 — Errors in Measurement · easy · theory
The relative error in a measurement is defined as:
A. The mean absolute error divided by the mean value ✓ Correct
B. The least count of the instrument
C. The mean absolute error itself
D. The absolute error multiplied by $100$
Solution: Being a ratio, it is dimensionless; multiplying by $100$ gives the percentage error.
Q30 — Errors in Measurement · easy · theory
Random errors in an experiment can be reduced by:
A. Taking a large number of readings and averaging them ✓ Correct
B. Changing the instrument each time
C. Using a single very careful reading
D. Ignoring the readings that differ most
Solution: Positive and negative fluctuations tend to cancel as the number of readings grows.