Conceptual Questions Based on Class 11 Physics Units and Measurements

Here we are providing conceptual questions for Class 11 Physics Units and Measurements. Answers are also provided along with questions. So that students can read and understand the question. These questions are prepared by the subject experts. Students can read these conceptual questions based on Circular Motion for better topic clarity and therefore will be able to score better marks in their exam.

Conceptual Questions Based on Class 11 Physics Units and Measurements

Conceptual questions based on class Units and Measurements is given below. Go through each and every question to understand the topic clearly.

Q.1. What is the necessity of selecting some units as fundamental units?

Solution. The number of physical units required to be measured is very large. If a separate unit is defined for each of them, then it will become very difficult to remember all of them as they will be quite unrelated to each other.

Q.2. Does the magnitude of a physical quantity depend on the system of units chosen?

Solution. No, the magnitude of physical quantity remains same in all systems of units.

Q.3. How is SI a coherent system of units?

Solution. In SI, all derived units can be obtained by multiplying and dividing the basic and supplementary units and no numerical factors are required to be introduced. So, SI is a coherent system of units.

Q.4. Comment on the statement: “To define a physical quantity for which no method of measurement is given or known has no meaning.”

Solution. The given statement is not correct. A physical quantity, if it is called so, must have a physical meaning. If it cannot be measured by any direct method, these must be some indirect method for its measurement. Entropy is one such physical quantity.

Q.5. Can an instrument be called precise with­out being accurate? Can it be accurate without being precise?

Solution. Yes, an instrument can be precise without being accurate, but the measurements cannot be accurate without being precise.

Q.6. What is meant by angular diameter of the moon? What is its value? Solution. The angle subtended by the two diametri­cally opposite ends of the moon at a point on the earth is called angular diameter of the moon. Its value is about 0.5°.

Q.7. Can there be a physical quantity that has no units and no dimensions?

Solution. Yes, strain is a physical quantity that has no units and no dimensions.

Q.8. Why is parallax method not useful for measuring the distances of stars more than 100 light years away?

Solution. For a star more than 100 light years away, the parallax angle is so small that it cannot be measured accurately.

Q.9. Do all physical quantities have dimen­sions? If no, name three physical quantities which are dimensionless.

Solution. No, all physical quantities do not have dimensions. The physical quantities like angle, strain and relative density are dimensionless.

Q.10. Can a quantity have different dimen­sions in different systems of units?

Solution. No, a quantity has same dimensions in all system of units.

Q.11. In defining the standard of length, (the prototype metre), we have to specify the temperature at which the measurement should be made. Are we justified in calling length a fundamental quantity, if another physical quantity (temperature) has to be specified in choosing a standard?

Solution. Yes, the choice of length as a fundamental quantity is justified. The modem definition of metre in terms of wavelength of light radiation is not affected by temperature.

Q.12. What is the basis of the principle of homogeneity of dimensions?

Solution. The principle of homogeneity of dimensions is based on the fact that only the physical quantities of the same kind can be added, subtracted or compared.

Q.13. Name two physical quantities having the dimensions [ML²T^-2].

Solution. Work and torque.

Q.14. If the units of force and length each are doubled, then how many times would the unit of energy be affected?

Solution. Energy = Work done = Force x length

So, when the units of force and length each are doubled, the unit of energy will increase four times.

Q.15. Write three physical quantities having dimensions [ML^-1T^-2].

Solution. Pressure, stress and Young’s modulus of elasticity.

Q.16. Can a quantity have dimensions but still has no units?

Solution. No, a quantity having dimensions must have some units of its measurement.

Q.17. Can a quantity have units but still be dimensionless?

Solution. Yes, for example, a plane angle has no dimensions but has unit like radian for its measurement.

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Conceptual Questions Based on Class 11 Physics

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