Units and Measurements — Previous Year Questions (Class 11 Physics)
Units and Measurements forms the foundation of all physics calculations. Master dimensional analysis, unit conversions, and significant figures to solve re
TL;DR: Units and Measurements forms the foundation of all physics calculations. Master dimensional analysis, unit conversions, and significant figures to sol…
Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated
Units and Measurements forms the foundation of all physics calculations. Master dimensional analysis, unit conversions, and significant figures to solve re
Units and Measurements — Previous Year Questions with Solutions
Q (2023, 2 marks): The length of a rod is measured to be 4.5 m. Express this length in cm, mm, and micrometers.
Answer: Given length = 4.5 m
1 m = 100 cm
1 m = 1000 mm
1 m = 10^6 micrometers
Length in cm = 4.5 × 100 = 450 cm
Length in mm = 4.5 × 1000 = 4500 mm
Length in micrometers = 4.5 × 10^6 = 4.5 × 10^6 μm
Q (2022, 3 marks): The diameter of a wire is measured using a screw gauge. The main scale reading is 2 mm and the circular scale reading is 45 divisions. If the least count is 0.01 mm, find the diameter of the wire.
Answer: Given:
Main scale reading (MSR) = 2 mm
Circular scale reading (CSR) = 45 divisions
Least count (LC) = 0.01 mm
Total reading = MSR + (CSR × LC)
Total reading = 2 + (45 × 0.01)
Total reading = 2 + 0.45
Total reading = 2.45 mm
Therefore, diameter of wire = 2.45 mm
Q (2023, 2 marks): Check the dimensional consistency of the equation v^2 = u^2 + 2as, where v and u are velocities, a is acceleration, and s is displacement.
Answer: LHS: v^2 has dimensions [LT^-1]^2 = [L^2T^-2]
RHS: u^2 has dimensions [LT^-1]^2 = [L^2T^-2]
2as has dimensions [LT^-2][L] = [L^2T^-2]
Since LHS = RHS = [L^2T^-2], the equation is dimensionally consistent.
Q (2024, 2 marks): The mass of an object is 5.65 kg and its volume is 2.3 m^3. Calculate the density of the object and express it in SI units.
Answer: Given:
Mass (m) = 5.65 kg
Volume (V) = 2.3 m^3
Density (ρ) = m/V
ρ = 5.65/2.3
ρ = 2.46 kg/m^3 (to 3 significant figures)
Density = 2.46 kg/m^3
Q (2023, 4 marks): A physical quantity P is related to four variables a, b, c, and d by the relation P = a^3b^2/(sqrt(c)d). If percentage errors in a, b, c, and d are 1%, 2%, 1%, and 2% respectively, find the percentage error in P.
Answer: Given: P = a^3b^2/(sqrt(c)d)
Percentage errors: a = 1%, b = 2%, c = 1%, d = 2%
For P = a^3b^2/(sqrt(c)d):
% error in P = |3 × (% error in a) + 2 × (% error in b) + 0.5 × (% error in c) + 1 × (% error in d)|
% error in P = |3(1) + 2(2) + 0.5(1) + 1(2)|
% error in P = |3 + 4 + 0.5 + 2|
% error in P = 9.5%
Q (2022, 1 mark): The wavelength of a light wave is 650 nm. Convert it to meters and express in scientific notation.
Answer: Given wavelength = 650 nm
1 nm = 10^-9 m
Wavelength = 650 × 10^-9 m = 6.50 × 10^-7 m
Frequently Asked Questions
What is the difference between precision and accuracy?
Precision refers to how close measurements are to each other (repeatability), while accuracy refers to how close a measurement is to the true value. A measurement can be precise but not accurate, or accurate but not precise.
How many significant figures should be reported in a calculation?
The result should have the same number of significant figures as the measurement with the fewest significant figures. For example, if multiplying 2.5 (2 sig figs) by 3.456 (4 sig figs), report the answer with 2 significant figures.
More Class 11 Physics PYQs
- Current Electricity
- Ray Optics
- Electrostatics
- Moving Charges and Magnetism
- Electromagnetic Induction
- Alternating Current
🤖 Stuck on any of these? Ask Syllab's free AI Tutor to explain step by step →