Measurement: Units, Conversion, Chart, Examples

The process of associating numbers with physical quantities and phenomena is known as measurement. The scope and applications of measurement are almost found in our everyday activities. For example, a ruler is used to measure the length of a piece of paper. This measurement can be expressed in different units.

However, this piece of paper can be measured in different ways. To help you understand how this piece of paper can be measured in different ways, here is a detailed article that explains to you all the concepts related to measurement.

Measurement and Examples

The textbook definition of measurement is the process of associating numbers with physical quantities and phenomena. To measure something, its quantity must be compared with a known quantity of the same type. Measurement is an activity done by us every day.

Let us understand the concept of measurement with common scenarios:

1. We begin our day by checking the time on the clock.
2. Sita visited a supermarket to purchase \(5\) kilograms of groceries and \(2\) litres of oil.
3. Ram visited the cloth shop to buy \(5\) meters of cloth.
4. If we are ill, our doctor will measure our temperature with a thermometer.

In the above examples of measurement, we see a few things are highlighted in bold and they are common in all the scenarios. These are some quantities to be measured and terms related to them. Let us see what measurement is and why we need it.

Measurement Systems

It is a set of units of measurement and rules governing these units. A unit means a standardized value of some quantity. There are mainly two systems of measurement:
(a) US Standard System
(b) SI System

US Standard System of Measurement

It is also called the Imperial or Customary unit system. It is derived from the British system and is still used in the US and some countries. In this system length is measured in the foot, mass is measured in the pound, and time is measured in seconds.

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SI System of Measurement

SI means International System of Units, or Systeme International d’Unites (from French). It is the standard international system used in most countries, including India.

Earlier, CGS (centimetre-gram-second) and MKS (metre-kilogram-second) systems were used to measure quantities and units.  SI is a more advanced version of the MKS system. The SI system has seven fundamental quantities and units and they are given below:

These are the base units, which are used to derive units.
Let’s take a look at some of the most commonly used SI and derived units.

Length

It is the distance between two points. To know how far one point is from another point on a horizontal level, we use the term length. For a vertical length, we use the terms height and depth. Width, breadth, thickness, radius, diameter are some terms related to length.

SI unit: meter \(\left( {\rm{m}} \right)\)
Measuring instruments: Ruler, measuring tape, meter scale, etc.

Very large units of length are astronomical-unit and light-years.
1. The astronomical unit is the mean distance between the centre of the sun and the centre of the earth.
2. Light year is the distance travelled by light in one year.

From the above data, we can see the vast difference in measurement of lengths in the universe, ranging from nanometres to light-years.

Mass

It is the amount of matter contained in an object. We use the term weight along with it.

SI unit: kilogram \(\left( {{\rm{kg}}} \right)\)
Measuring instruments: Weighing scale, weighing balance, digital scale, etc.

Time

The duration between two events is called time.

SI unit: second \(\left( {\rm{s}} \right)\)
Measuring devices: Watch, clock, calendar

Watch and clock measure time in seconds, minutes, and hours. A calendar is a written record of days, weeks, and months in a year.
Earlier, hourglass, sundial during the day, candle clocks during the night were used to measure time.

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Temperature

It is a measure of how hot or cold something is. It is the quantity that is created due to heat or thermal energy. We say a person with a fever has a high temperature. Similarly, we feel ice at low temperatures.
SI unit: Kelvin \(\left( {\rm{k}} \right)\)
Commonly used unit is Celsius.

Measuring Devices: Thermometer, thermocouple.
Mercury thermometers have been used for a long time to measure temperature. Now, digital thermometers, and contactless infrared thermometers are also used.

US system uses the Fahrenheit scale.

The lowest temperature any object can go to is \(- 273.15\,^\circ {\rm{C}}.\) This is \(0\,{\rm{K,}}\) called the Absolute Zero.

Electric Current

Electric current is defined as the rate of flow of charges through a wire in unit time.
\({\rm{Current}}\;I = \;\frac{{{\rm{Charge}}\;\left( Q \right)}}{{{\rm{time}}\;\left( t \right)}}\)

SI unit: ampere \(\left( {\rm{A}} \right)\)
Measuring device: Ammeter

Speed

It is the distance covered at a certain time. The scientific unit is metres per second \(\left( {{\rm{m}}\,{{\rm{s}}^{ – 1}}} \right).\) The speedometer in our vehicles shows the current speed of the vehicle in kilometres per hour \(\left( {{\rm{km}}\,{{\rm{h}}^{ – 1}}} \right).\)

Area

It is a two-dimensional quantity derived from length. Small areas are measured in \({\rm{c}}{{\rm{m}}^2},{{\rm{m}}^2}.\) Land area is usually measured in acres. Large areas such as the area of a state or country are identified in square kilometres.

Capacity

It is the volume or amount of substance an object can hold or contain. Volume is a three-dimensional quantity. We measure liquids and gases by their capacity.

SI unit: litre \(\left( {\rm{l}} \right)\)
Measuring devices: Measuring cup, beaker

\(1\) litre is the volume of a cube of sides \({\rm{10}}\,{\rm{cm}}{\rm{.}}\) Hence \(1\) litre is also equal to \(1000\) cubic centimetres. Volume is a derived quantity based on length.

Density

It is the ratio of the mass of an object to its volume. Therefore, its SI unit is \({\rm{kg}}\,{{\rm{m}}^{ – 3}}.\)
\({\rm{Density}} = \frac{{{\rm{mass}}}}{{{\rm{volume}}}}\,{\rm{kg}}\,{{\rm{m}}^{ – 3}}\)

Pressure

It is the force applied to a unit area. The SI unit for pressure is Pascal. It is derived from units of force and area.
\(1\,{\rm{Pa}} = \frac{{1\,{\rm{Newton}}}}{{1\,{{\rm{m}}^2}}} = \frac{{{\rm{kg}}}}{{{\rm{m}}\,{{\rm{s}}^{ – 2}}}}\)

Solved Questions on Measurement

Q.1. Convert \(60\,{\rm{mm}}\) to SI system of length.
Sol:
\(1\;\,{\rm{m}} = {10^{ – 3}}\,{\rm{m}}\)
\(\Rightarrow {\mkern 1mu} 60\;{\mkern 1mu} {\rm{mm}} = 60 \times {10^{ – 3}}\,{\rm{m}} = 0.06\,{\rm{m}}\)

Q.2. Convert \( – 40\,^\circ {\rm{C}}\) to Fahrenheit scale.
Sol:
The formula to convert Celsius to Fahrenheit is
\(F = \left( {C \times 1.8} \right) + 32\)
\(F = \left( { – 40 \times 1.8} \right) + 32 = – 40\,^\circ {\rm{F}}\)
Hence \(- 40\,^\circ {\rm{C}}\) is equivalent to \(- 40\,^\circ {\rm{F}}\)

Summary

Measurement is something we all do almost every day. We also do non-standard measurements such as using our hands, fingers, feet to measure small lengths quickly. We need an accurate measurement to measure the appropriate devices to know the correct amount or quantity of things we use.

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FAQs

Q.1. Why is a thermometer used when we have a fever?
Ans: Fever is the condition when the body temperature rises from normal. To know the amount of temperature the body has risen above normal, a clinical thermometer is used.

Q.2. Why are body parts not used for measuring lengths?
Ans: Every person is different. The height, weight of each person varies. So, hand span, pace, cubits are not used in the measurement.

Q.3. Why are kilometres not used to measure the distance between stars?
Ans: Any two stars are placed millions and millions of kilometres apart. The numbers are too huge to write. So, a light-year is a convenient way of writing large distances.

Q.4. Are there some liquids that are measured in kilograms and in litres?
Ans: Usually cooking oils are measured in kilograms and their capacity is mentioned in litres.

We hope the topics covered in this article on Measurement has helped you in understanding the concept in detail. However, if you have any queries on the same, ping us through the comment box below and we will get back to you as soon as possible.