Measurements MCQs
Inter · Physics (11th) · 6 questions
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11th class physics: Measurements
Physics starts with measuring. The SI system has seven base quantities and units: length (metre), mass (kilogram), time (second), electric current (ampere), temperature (kelvin), amount of substance (mole) and luminous intensity (candela). Every other quantity is derived from these, and its dimensions show how: force is [MLT⁻²], energy [ML²T⁻²] and momentum [MLT⁻¹]. Dimensional analysis checks whether an equation can be right (both sides must have the same dimensions) and helps derive relations, though it cannot find pure numbers like 2π. Prefixes scale units: milli 10⁻³, micro 10⁻⁶, nano 10⁻⁹, pico 10⁻¹²; kilo 10³, mega 10⁶, giga 10⁹. Significant figures show precision: leading zeros never count, trailing zeros after a decimal point do. Uncertainty: percentage uncertainty = (absolute uncertainty ÷ value) × 100; when quantities are multiplied or divided, their percentage uncertainties add, and a power multiplies them.
Questions with answers
Written by Parcha from the syllabus. Samples until a subject reviewer checks them; report anything wrong from the practice screen.
Q1 · Parcha original · Sample
How many base units are there in the SI system?
- A. 5
- B. 6
- C. 7
- D. 9
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Answer: C. 7
The SI has seven base units: metre, kilogram, second, ampere, kelvin, mole and candela. All other units (newton, joule, watt…) are derived from them.
Open this question on its own pageQ2 · Parcha original · Sample
Which of these is a base quantity?
- A. Force
- B. Velocity
- C. Energy
- D. Mass
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Answer: D. Mass
Mass (kilogram) is one of the seven base quantities. Force, velocity and energy are derived: for example, force is mass × acceleration.
Q3 · Parcha original · Sample
How many significant figures are there in 0.00450?
- A. 2
- B. 3
- C. 5
- D. 6
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Answer: B. 3
Leading zeros only place the decimal point and are not significant. The 4, the 5 and the trailing zero after the decimal point are significant, giving 3.
Q4 · Parcha original · Sample
The dimensions of force are:
- A. [MLT⁻²]
- B. [MLT⁻¹]
- C. [ML²T⁻²]
- D. [MT⁻²]
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Answer: A. [MLT⁻²]
Force = mass × acceleration = [M] × [LT⁻²] = [MLT⁻²]. [ML²T⁻²] is energy and [MLT⁻¹] is momentum.
Q5 · Parcha original · Sample
The prefix "nano" stands for:
- A. 10⁻⁶
- B. 10⁻¹²
- C. 10⁹
- D. 10⁻⁹
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Answer: D. 10⁻⁹
Nano (n) = 10⁻⁹. Micro (μ) = 10⁻⁶, pico (p) = 10⁻¹², and giga (G) = 10⁹.
Q6 · Parcha original · Sample
A length is measured as 2.0 ± 0.1 cm. The percentage uncertainty is:
- A. 0.1%
- B. 2%
- C. 5%
- D. 10%
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Answer: C. 5%
Percentage uncertainty = (absolute uncertainty ÷ measured value) × 100 = (0.1 ÷ 2.0) × 100 = 5%.