Physical Quantities and Standard International Units

As you are going to use your instrument, you need to learn physical quantities and SI measurement units. It’s important to understand what thing of an object you are going to measure and how to express it in a value and measurement unit. Both physical quantities and unit measurement are basic understanding that you have to have in your mind before using your instrument.

Physical Quantities

Length is a base physical quantity

Physical quantities are physical characteristics of an object that can be measured or expressed in value and units.

Everything should be measurable. From a table’s length that we measure by a tape meter to the brainwave that we measure by EEG. As science, engineering, and technology evolve, human manipulate sources in such a way in order to create measurement tools.

When you are preparing to buy a measuring tool, you have to know what physical quantity you are going to measure and the measurement unit that you understand certainly. For instance, you want to measure a table length, then you have to find out measuring tool for length. And because you are familiar with inch, then look up the measuring tool that uses inch.

Actually, there are countless physical quantities applied in measurement. Therefore, it’s better off classifying them into 2 divisions: base quantities and derived quantities.

1. Base Quantities

Base quantities are the very basic physical quantities that most physical quantities originate from them. There are only 7 base quantities: length, time, electric current, temperature, mass, luminous intensity, and amount matter.

2. Derived quantities

All physical quantities are actually derived quantities, except the 7 base quantities above. Derived quantities are physical quantities obtained from base quantities. Some of the derived quantities which we can find in our daily life are area, volume, pressure, speed, acceleration, etc.

Standard International Measurement Units

Suppose you have measured the length of a table, and it’s 2 times of your steps. The 2 is the value and the step is the unit. However, it’s not easy for anyone to accept your foot as the standard measuring unit since the length of your step is not constant. It could be very missleading. Therefore, it’s critical to have a unit that is agreed by international convention so that everyone can recognize it.

The convention acts to decide which units have to use, so that all the people around the world can use it. People share the same understanding of the measuring result is.

There are a huge number of measurement units. However, there are some important standard international units (SI Units) that we have to know altogether.

No.Physical QuantitiesUnits (SI)Sym
1Lengthmeterm
2Masskilogramkg
3Timeseconds
4TemperaturekelvinK
5Electric CurrentAmpereA
6Luminous IntensityCandelacd
7Amount of Mattermolemole

So, wherever you go, when you use meter unit, people have understood how long it is. Similarly, people will easily recognize the mass you mean by saying 1 kg. However, if you are familiar with your own length unit, just go on. You could easily convert it to the meter unit whenever you want.

To Sum Up

When we use a measuring instrument, our measuring target is a particular or some physical quantities. We use value and units to express them. We also can convert it to the international unit ones to let others from another country could understand how many they are. By understanding physical quantities and Standard International (SI) units, we know what unit we should use to let everyone knows. The important thing is we know how to use an instrument and tell the results in an appropriate unit.

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