## 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 [M^{0}LT^{-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 ^{-1}T^{-2}]?**

Ans: Pressure, Stress and Young’s modulus have the same dimension of [ML

^{-1}T

^{-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.