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Units and Measurements Class 11 Notes for NEET, JEE & CUET (With Topic-wise MCQs & Answers)

Understanding Units and Measurements from NCERT Class 11 Physics is essential for NEET, JEE and CUET aspirants. Students frequently search for how to calculate least count in screw gauge for NEET physics, dimensional analysis shortcut tricks for JEE, how to find significant figures in measurements, and important solved numericals on vernier calipers and screw gauge for NEET. This chapter forms the base for experimental physics, measurement techniques, and error handling in higher-level physics.

This guide provides clear theory, integrated MCQs, Assertion–Reason questions and topic-focused practice — ideal for last-minute revision and concept reinforcement.

1. Understanding Physical Quantities, Units & Systems of Measurement

A physical quantity is anything that can be measured. It requires:

  • Numerical value

  • Appropriate unit

The SI system is internationally accepted. It consists of seven base units: metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol), and candela (cd).

Students preparing for JEE Mains Chapter 1 often look for Units and Measurements NCERT short notes for last-minute revision, and this section forms the root of that revision.

MCQs — Basic Concepts of Units

Q1. Specific gravity of a fluid is a dimensionless quantity because:
Reason: It is the ratio of density of fluid to density of water.
a) Both Assertion and Reason correct & Reason explains Assertion
b) Both correct but Reason does not explain
c) Assertion correct but Reason incorrect
d) Both incorrect

Answer: a

Q2. In a system where mass = 1 quintal, length = 1 km, time = 1 hour, one Newton is equal to:
a) 1 unit
b) 129.6 unit
c) 125.7 unit
d) 103 unit

Answer: b

2. Significant Figures & Rounding-Off Rules

Significant figures reflect the precision of measurement. They depend on:

  • Least count of the instrument

  • Accuracy of the measuring process

Students preparing for NEET frequently search for how to find significant figures in measurements NEET level problems, which makes this section highly important.

MCQs — Significant Figures

Q3. Assertion (A): The number 0.00764 has three significant figures.
Reason (R): Zeros to the left of first non-zero digit are not significant.
a) Both true, R is correct explanation
b) Both true, but R not explanation
c) A true, R false
d) A false, R true

Answer: a

Q4. The number of significant figures in 0.002305 is:
a) 6
b) 4
c) 7
d) 2

Answer: b

Q5. The number of significant figures in 0.30100 is:
a) 1
b) 3
c) 5
d) None

Answer: c

Q6. Density of a metal cube: mass = 5.74 g, volume = 1.2 cm³. Density to correct significant figures is:
a) 4.8 g/cm³
b) 4.78 g/cm³
c) 4.783 g/cm³
d) 5.0 g/cm³

Answer: a

3. Errors in Measurement (Absolute, Relative & Percentage Error)

Error analysis is one of the most tested topics in NEET/JEE. Students often search for how to solve error propagation questions in Units and Measurements JEE, especially the rules:

  • For addition/subtraction → absolute errors add

  • For multiplication/division → percentage errors add

  • For powers → multiply error by power

MCQs — Error Analysis

Q7. If time period = 2.5 s measured using a stopwatch with least count 0.5 s, the percentage error is:
a) 10%
b) 30%
c) 15%
d) 20%

Answer: d

Q8. If error in measuring radius of a sphere is 2% and mass error is 3%, error in density is:
a) 5%
b) 7%
c) 9%
d) 11%

Answer: c
(ρ = m/r³ → error = 3% + 3×2% = 9%)

Q9. Period of 20 oscillations measured as 25 s using stopwatch LC = 0.2 s. Percentage error =
a) 8%
b) 1.8%
c) 0.8%
d) 0.1%

Answer: c

4. Vernier Calipers: Least Count, Zero Error & Measurement

Vernier calipers are essential tools for NEET/JEE experimental questions. Many students face difficulty understanding vernier constant and search for important solved numericals on vernier calipers and screw gauge for NEET.

Vernier Constant (VC) = 1 MSD – 1 VSD

MCQs — Vernier Measurements

Q10. Vernier scale has 25 divisions coinciding with 24 MSD; MSD = 0.5 mm. VC =
a) 0.001 cm
b) 0.002 cm
c) 0.01 cm
d) 0.02 cm

Answer: b

Q11. Which vernier gives VC = 0.01 mm?
a) 9 mm / 10 divisions
b) 95 mm / 100 divisions
c) 99 mm / 100 divisions
d) 9 mm / 100 divisions

Answer: c

5. Screw Gauge: Pitch, Least Count & Zero Error

Students preparing for NEET often search specifically for how to calculate least count in screw gauge for NEET physics.
Formula:

  • Pitch = distance moved in one full rotation

  • Least Count = Pitch / Number of divisions on circular scale

MCQs — Screw Gauge

Q12. Screw gauge pitch = 0.5 mm, circular scale = 50 divisions. LC =
a) 0.0001 cm
b) 0.0025 cm
c) 0.01 cm
d) 0.001 cm

Answer: d → LC = 0.5/50 = 0.01 mm = 0.001 cm

Q13. Screw is rotated 6 turns and moves 3 mm. If 50 divisions exist, LC =
a) 0.001 cm
b) 0.01 cm
c) 0.02 cm
d) 0.001 cm

Answer: a

Q14. Spherometer with 20 threads/cm and 100 circular divisions has LC:
a) 5 μm
b) 50 μm
c) 0.5 μm
d) 0.05 μm

Answer: a

6. Dimensional Analysis & Applications

Dimensional analysis is one of the most critical JEE topics. Students frequently search for dimensional analysis shortcut tricks for JEE aspirants.

Use rules:

  • Same dimensions → can be added/subtracted

  • Dimensional homogeneity must hold

MCQs — Dimensions

Q15. Assertion: Energy per unit volume and angular momentum can be added.
Reason: Only quantities with same dimensions can be added.
Correct answer: d (A is false, R is true)

Q16. Time period of oscillation of liquid drop:
T = K √(ρ r³ / S³/₂)
Assertion claims it’s correct; Reason claims RHS has wrong dimensions.
Correct answer: d

7. Combined Conceptual Practice (Mixed MCQs)

Q17. In Poiseuille’s method, the most accuracy-demanding measurement is:
a) pressure difference
b) volume collected
c) length of tube
d) inner radius of tube

Answer: d

Q18. A cylinder: length = 10.1031 cm, diameter = 2.0935 cm. Volume correct to proper SF:
a) 139.04 cm³
b) 34.76 cm³
c) 134.75 cm³
d) 46.35 cm³

Answer: b

Q19. Area of square is 5.29 cm²; area of 7 squares:
a) 37.030 cm²
b) 37.0 cm²
c) 37.03 cm²
d) 37 cm²

Answer: b

Q20. Difference: 9.99 m – 0.0099 m =
a) 9.98 m
b) 9.980 m
c) 9.9 m
d) 9.9801 m

Answer: a

Conclusion

This medium-length guide integrates conceptual explanation and topic-wise MCQs, covering significant figures, vernier calipers, screw gauge, dimensional analysis, and error handling — all essential for NEET, JEE and CUET physics. Combined with long-tail search queries like Units and Measurements mock test for NEET/JEE, NEET physics error analysis questions, and JEE level problems on units and dimensions, this blog post helps target exactly what students search for and what exams frequently test.

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