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Introduction
Measurement play a very important role in our daily lives. It is a basic of scientific studies and experiments.
We all take measurements weather we are at home, in a shop or at a doctors required to make a dress, your needs to measure length.
When we buy items search has food vegetable, salt, sugar and wheat the shopkeeper measure the quality. This invoice the measurement of mass. The amount of petrol required to be filled in a car and the amount of milk required at home invoice measurement of volume.
Form the above examples, we see the accurate measurement are required in our day to day activities. We open need to measure length area mass and volume. Quality that can be measure is called a physical quality.
What is measurement?
The comparison of an unknown quantity with a non fix quality of the same kind is called measurement. The non fix quantity is called unit.
Every measurement consists of two parts. The first part is numerical value (number) and the second part is the unit of measurement. For example , when we say ,
'add 3 spoonfuls of sugar to a glass of milk the unit used is a spoon full ( quality measured by a spoon ) and 3 is the numerical value.
Similarly, when you see a board saying the distance of Pune is 30 km the numericals value that is used is 30 and the unit of measurement is kilometre. This means that the distance from that point to Pune is 30 times the standard length of 1 kilometre.
It must we kept in mind that the measurement of a physical quantity is completely only if it has both:
- The numerical value that indicate how many times the unit is contained in the given physical quality being measured and
- The unit of measurement of the physical quantity.
Any measurement without these two is considered incomplete or wrong. Thus, physical quality has a number value and a unit of measurement.
Early units of measurement
Earlier people use their different body parts of measurement. Some of them were as follows:
Handspan : The distance from the tip of the thumb to the tip of the little finger of an outstretched hand .
Cubit : the length from the elbow to the tip of the middle finger.
Foot pace : the distance of one full step.
Yard : the distance from nose to the throm of the outstretched hand.
Need for standard units of measurement
Body parts cannot be used as reliable units of measurement because the length of various parts of the human body differ from person to person. Likewise, to measure the volume of milk, you cannot use a spoon or a thumbler as these are available in various sizes. Thus, these is a need of units of measurement which can be uniformly used by everyone. Search units are called standard units of measurement. Thus, standard unit is a unit which always has the same measurement for everyone.
Standard units for measuring physical quantities
Still a few year ago, different countries had their own system of measurement. This was very confusing. In the year 1960 the general conference of weight and measurement recommended that a common system should be used all over the world. This system is called the SI system of units. SI standard for système Internationale d' Unitès ( in French ) . The SI system of units is used uniformly all over the world for all scientific work.
Standard units of different physical quality and their symbols.
| Base quality | Unit | Unit symbol |
|---|---|---|
| length | metre | m |
| mass | kilogram | kg |
| time | second | s |
| electric current | ampere | A |
| template | kelvin | K |
| amount of a substance | mole | mol |
| luminous intensity | candela | cd |
Rules to write the SI unit correctly.
These are the same rule that should be followed to write the SI unit correctly.
- Name of units are written in lower case. For example , metre, kilometre and second.
- Unit named after scientists are written in lower case. For example, Kelvin , Newton and joule.
- Symbols for the units are always written in lower case. For example, m, kg and s. However, the symbols for the units derived from the names of scientists are written in capital letter. For example, °C ( degree Celsius ) , K ( Kelvin) , N ( Newton ) and J ( joule ).
- Symbols are not followed by a full stop . For example, we write ' it is 75 cm long' and not it is 75 cm. long' . If the symbol of occurs at the end of a scientist, it is followed by a full stop indicating the end of the sentence.
- Symbols are never written in plural. For example, we write 1 m, 100 m, not 100 ms.
| Know more about measurements | Available |
|---|---|
| Measurements of length | CLICK NOW |
| Measurements of area & Volume | CLICK NOW |
| Measurements of mass | CLICK NOW |
