We measure various things in our daily life. In the past, measurements were done using different parts of human body. For e.g. Feet, handbreadths, fathom etc. But there are many limitations on accuracy of such measurements. For e.g. length of handbreadth varies from a person. Therefore, need of standard measurement practices was emerged. The method of measurement depends upon the accuracy required. In this chapter, we are going to study measurement, commonly used units, basic units and derived units.
After reading this lesson, you will be able to:
• Know Importance of measurement, SI units.
• Understand Quantitative and Qualitative measurements.
• Know Base Units and derived units.
• Understand Least Count of instruments.
• Estimate weight of goods.
1.3 Importance of measurement
In today’s world, we cannot do without measurement. Grocery shop owner needs to measure weight, doctors measures temperature, blood pressure, Two wheeler mechanics measures tyre pressure, milkman measures milk, mesons measures wall length etc. Measuring units become essential part of proper communication.
1.4 Quantitative and Qualitative measurements
We get new information everyday and from this information, we
derived knowledge. “This year we got good yield of rice”. This is a
descriptive (qualitative) information. “This year we produce ten quintal rice”; this is quantitative information. Quantitative information is more useful than the descriptive information. Science
depends upon such quantitative information. Therefore, it is necessary to measure all the characteristics. Few examples of qualitative and quantitative informations are given below:
Please refer table.1 for more examples. This ‘little’, ‘sufficient’, ‘good’, ‘enough’, ‘lot’ are the example of qualitative information. Whereas, quantitative information like 200ml, Rs.20, 2 chapattis, 5 quintals, 500mm, 5 bags gives specific information. Recording everything is basic requirement for improving productivity. Collecting proof, based on quantitative information is must to support your invention.
| Qualitative Information
|| Quantitative Information
| Give me little water
|| Give me 200 ml water
| Give me some money
|| Give me Rs.200/-
| I ate sufficient food
|| I ate two chappatis
Intext questions 1.1
Identify Quantitative and Qualitative information:
1) We got good yield of crop. .
2) We got 5 quintals of rice. .
3) This year there is enough rain. .
4) This year we got 500mm rain. .
5) This construction needs lot of cement. .
6) This construction needs 5 bags of cement. .
1.5 Measurement and SI units
Measurement is nothing but a measuring attribute of an object with other known attribute of similar object. The known things are called standards. In the past, there were different standard of measurement in different countries. Prominent among them are British standards and French Metric system. Now there are international standards (SI) for measurement.
In our country only use of SI standard is legal. Therefore, you will find only SI units in all Government contracts and agreements. We will discuss only SI units in our study. Different measuring parameters and their measuring units are shown in the table below: