Class 11 Physics Physical World and Measurement MCQs (Difficulty-wise) with Answers
If you’re revising this chapter for school exams, practising level-wise helps you build confidence: start with units and basic dimensions, then move to significant figures, errors, and dimensional analysis. Below is a difficulty-wise set for Physical World and Measurement with short explanations.
Easy (Level 1)
Question 1
Which of the following is a correct SI base unit–quantity pair?
A. Ampere – electric current
B. Joule – temperature
C. Newton – length
D. Watt – mass
Correct Answer: A
Explanation: Ampere (A) is the SI base unit of electric current. Joule, newton, and watt are derived units.
Question 2
The CGS system uses which base units?
A. centimetre, gram, second
B. metre, kilogram, second
C. centimetre, kilogram, second
D. metre, gram, second
Correct Answer: A
Explanation: CGS stands for centimetre–gram–second.
Question 3
The dimensional formula of volume is:
A. $[M^0 L^3 T^0]$
B. $[M^1 L^3 T^0]$
C. $[M^0 L^2 T^{-1}]$
D. $[M^0 L T^0]$
Correct Answer: A
Explanation: Volume depends only on length: $V \sim L^3$.
Medium (Level 2)
Revision Tip: For any formula, check two things quickly: (1) units on both sides match, (2) the final quantity has the expected dimension.
Question 4
Only physical quantities with the same dimensions can be added or subtracted. This statement is called:
A. Principle of superposition
B. Principle of homogeneity of dimensions
C. Principle of uncertainty
D. Principle of relativity
Correct Answer: B
Explanation: Homogeneity means every term in a physical equation must have the same dimensions.
Question 5
Which statement about dimensional analysis is correct?
A. It proves an equation is correct in every detail.
B. It checks whether an equation can be dimensionally consistent.
C. It allows addition of quantities with different dimensions.
D. Trigonometric functions can take dimensional arguments.
Correct Answer: B
Explanation: Dimensional analysis is a necessary check, but it cannot confirm numerical constants or functional form completely.
Question 6
Assertion (A): The number of physical quantities is very large, but only a limited number of base units are needed. Reason (R): Many physical quantities are related, so their units can be expressed in terms of base units.
A. Both A and R are true and R is the correct explanation of A
B. Both A and R are true but R is not the correct explanation of A
C. A is true but R is false
D. A is false but R is true
Correct Answer: A
Explanation: Derived units (like newton, joule) are built from base units, so a small base set covers many quantities.
Question 7
The SI unit kelvin (K) is defined by fixing the numerical value of the:
A. Planck constant
B. Boltzmann constant
C. Avogadro constant
D. Elementary charge
Correct Answer: B
Explanation: The kelvin is defined by fixing the value of the Boltzmann constant $k$.
Hard (Level 3)
Revision Tip: When significant figures and errors appear together, write the measurement first, then round at the final step.
Question 8
Both plane angle (radian) and solid angle (steradian) are:
A. Dimensionless quantities
B. Quantities with dimensions of length
C. Quantities with dimensions of area
D. Quantities with dimensions of time
Correct Answer: A
Explanation: Radian and steradian are treated as dimensionless in SI because they are ratios of lengths/areas.
Question 9
Assertion (A): Magnitudes are considered in dimensional analysis. Reason (R): Dimensions represent the nature of a physical quantity, not its magnitude.
A. A is false but R is true
B. Both A and R are true and R is the correct explanation of A
C. Both A and R are false
D. A is true but R is false
Correct Answer: A
Explanation: Dimensional analysis uses only the type of quantity (M, L, T, etc.), not numerical values.
Question 10
If a quantity has dimensions $[M^1 L^2 T^{-3}]$, it can represent:
A. Power
B. Force
C. Pressure
D. Momentum
Correct Answer: A
Explanation: Power is energy per unit time: $[M L^2 T^{-2}]/[T] = [M L^2 T^{-3}]$.
Want a mixed set for quick revision? Go back to: Class 11 Physics Physical World and Measurement MCQs (Mixed).
If you got stuck on any question, revise the definition (unit/dimension) first and then retry the MCQ without looking at the answer.