Download Now
Important Questions Collection
Short Questions with Answer
Unit: Units and Measurement
Science | Physics Class 11
1. Can we tell the unit of a physical quantity from its dimensions?
Ans: Yes, we can tell the unit of a physical quantity from its dimensions. For example, if a physical quantity has the dimension [M0LT-1] then its SI-unit will be ms-1.
2. Can dimensional analysis tell you that a physical relation is completely right?
Ans: The numerical factor in relation cannot be determined. Therefore Dimensional analysis cannot tell us that a physical relation is completely right.
3. What is the importance of base units?
Ans: There are seven base units in SI-units and all physical quantities can be expressed in term of these base units.
4. Do all the constants carry dimension?
Ans: No, all the constants do not carry dimensions but some constants carry dimensions. For example G is a constant which has a dimension.
5. Which physical quantities have the same dimensions of [ML-1T-2]?
Ans: Pressure, Stress and Young’s modulus have the same dimension of [ML-1T-2].
6. Can a physical quantity have unit but is dimensionless?
Ans: Yes, it is possible to have unit but no dimension. For example angle has no dimension but has the unit of radian.
7. What are characteristics of a physical standard?
Ans: A physical standard must have following characteristics:
(i) Invariability
(ii) Accessibility
(iii) Indestructibility, and
(iv) Reproducibility
8. Does the measurement of a physical quantity depend upon the system of units used?
Ans: It doesn’t depend on the system of units. There is only change in the numerical value of the physical quantity.
9. Do you think that a definition of a physical quantity for which no direct method of measurement is known or given has a physical meaning?
Ans: Yes, the measurement may be made by indirect method.
10. Can you suggest a way to measure length along a curved line?
Ans: The length along a curved line may be measured by the technique of trajectory or by measuring the length of string by placing t on the curved line.
