Class 11 Physics - Units & Measurement Full Mock Test

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Subjective Section (Answer briefly and clearly):

Q21. Define fundamental and derived units with two examples each.

Q22. What are the advantages of SI system over other systems of units?

Q23. State the principle of dimensional homogeneity. Why is it important?

Q24. Explain the concept of significant figures with an example.

Q25. What is parallax method? Where is it used?

Numerical Section:

Q26. The value of G in SI units is 6.67×10^-11 N·m²/kg². Convert it into CGS units.

Q27. If the length of a rod is measured as 3.56 cm, 3.54 cm, and 3.55 cm, find the mean value and absolute error.

Q28. Find the dimensions of Planck’s constant (h) given E = hν, where E is energy and ν is frequency.

Q29. Check whether the equation v = at is dimensionally correct, where v is velocity, a is acceleration, t is time.

Q30. A sphere has a radius of 2.00 cm measured to the nearest 0.01 cm. Calculate the percentage error in the measurement of radius.

Subjective Section - Suggested Answers

1. Fundamental units: Units which are independent and cannot be derived from other units (e.g., meter, kilogram).
   Derived units: Units derived from fundamental units (e.g., Newton, Joule).
2. Advantages of SI: Universally accepted, decimal-based, easy conversions, covers all physical quantities.
3. Dimensional homogeneity: All terms in a physical equation must have the same dimensions. It ensures correctness of equations.
4. Significant figures: Digits in a measurement that are known reliably plus the first uncertain digit. Example: 2.305 (4 significant figures).
5. Parallax method: Used to measure large distances (e.g., distance to stars) by observing apparent shift from two positions.

Numerical Section - Suggested Solutions

1. Q26 Solution:
   G_CGS = 6.67×10^-8 dyne·cm²/g²
2. Q27 Solution:
   Mean = 3.55 cm; Absolute error = 0.01 cm
3. Q28 Solution:
   [h] = [E]/[ν] = [ML²T^-2]/[T^-1] = [ML²T^-1]
4. Q29 Solution:
   Yes; [v] = [LT^-1], [at] = [LT^-2]×[T] = [LT^-1]
5. Q30 Solution:
   Percentage error = (0.01/2.00) × 100 = 0.5%