B. Descriptive type questions.
1. What are the limitations of using our senses and body parts for measurement?

2. Define the following key concepts

(i) Estimation
(ii) Standard of measurement
(iii) Standard metre
(iv) Time interval
(v) Pendulum

3. Name the SI units used to measure length, mass, time and temperature.

4. Give four examples of periodic systems?

5. Define amplitude and time period of a pendulum.

6. Airplane pilot cannot use his senses to guide his plane through thick clouds. He must depend on the plane’s instruments. Why?

7. In a village 100 acres of land was distributed among ten farmers. The farmers were very happy because all of them got equal-sized plot of land. How did the Head of the Panchayat manage to do this?

8. Goldsmith uses a balance to measure gold ornaments. Why does he use an instrument for this purpose?

9. In 100 metre race, you must have seen that for each athlete the judge looks at a stop watch to measure the ‘time’ required by the athlete to complete 100 metres. What does this ‘time’ mean?

10. Describe the method for finding out the area of a leaf.

11. Measure the diameter of a glass marble by using a scale and two wooden blocks. Which other instrument can be used for finding it more accurately? Why?

12. A thin wire is closely wound on a pencil with its successive turns in contact with each other. If turns of the wire occupy a total distance 2 cm, what is the diameter of the wire. Which other instrument can be used for more accurate result?

13. How much volume of petrol is needed to fill a spherical tank of radius 2.1 m?

14. Why a standard reference is taken as a unit?