hectare

The hectare is equivalent to 100 ares in the metric system, or 10,000 square metres, and to 2.471 acres in the British Imperial System and US Customary measure. It is derived from the Latin word area and from hect, an irregular contraction of the Greek word for hundred. Although the hectare is the most commonly used unit of land measurement, the are is the primary metric unit. According to subsequent definitions, a hectare is equal to a djerib in Turkey, a jerib in Iran, a gong qing in mainland China, a manzana in Argentina, and a bunder in the Netherlands.

The standard unit of measurement specifies the magnitude of a quantity in a quantifiable language. It helps to understand the relationship between the object and the measurement. Kids don't automatically understand how to measure things, even though measurement is an important part of life. The purpose of this article is to explain in detail the different units and measurements and why we need them.

Take the example of a man who wants to buy a red shirt from the store. His only language is English. The man replies, "Ureed qameesan ahmar alawn". The shopkeeper says, “What?!” The man asked for a red coloured shirt, but he said it in Arabic. Obviously, the shopkeeper couldn’t understand anything since it was not a standard language.

Similarly, there are many systems and units in place for measuring different quantities like length, area, mass, volume and other things. For example, an acre is a common way of representing area measurement in India. One acre is around 4046 square meters if you look at the metric system. So now you can guess how difficult it would be if there were no standard units and measurement.

Similarly temperature is measured in degree celsius and the same unit of measurement cannot be used to measure the length of a rod. Each quantity has to be measured in its own way. Magnitude and the measurement varies along with the quantity. Hence the need for the units of measurement for each quantity arises. 

To tackle this problem of different systems of measurement (just like the different languages), a system of units called the International System of Units was established and has been adopted by most developed and developing countries. Although this has been established and adopted across major fields like science and technology and government operations, normally people still refer to their customary or traditional units. For example, in the United States of America people even now refer to lengths in terms of inches and feet instead of centimetres and meters.After learning the importance of units and measurements, let us focus on the International System of Units. Traditionally, people didn’t have any measuring devices to calculate standard measurement units. To tackle this problem they came up with different innovative ways of measuring with the tools available at hand. For example, they used a foot as a measurement of length. 1 foot is around 0.3 meters which is 30 cm. Another measurement our ancestors used for length was a league. One league was the amount of distance covered by a person when we walked for an hour. This unit, however, is no longer in use.

The International System of Units or SI units defines standard units for measurement of all physical quantities.

In principle, any physical quantity can be expressed in terms of seven base units.

Apart from the base units, there are SI units of derived units. These are called as such because their value is determined based on one or more base units. Some examples are given below.

The SI system utilizes a standard system of prefixes to the basic units that allow them to be more relevant to and descriptive of relative magnitude. Prefixes are used to identify the multiples or the fractions of the original unit. There are 20 accepted prefixes. The table below lists the standard prefixes for the SI units of measurement

Can a quantity have dimensions but no units associated with it?

No. If a quantity has dimensions then it should have units associated with it.

Measurement of a physical quantity is defined in terms of its dimensions. Dimensions are measured in terms of length, mass, and time as represented by L, M, and T.

Any given physical quantity is measured in comparison to a basic unit that is arbitrarily chosen, internationally accepted. The result of a measurement is expressed by a number which is accompanied by a unit.

Supplementary units are dimensionless physical quantities that are used along with fundamental units.

Give an example of Derived units.

Velocity is a physical quantity derived from fundamental quantities of length and time.

The unit of velocity is ms-1.