measurement

Measurement is finding a number that shows the size or amount of something.

Without measurement, it would be hard to know when your school starts, when the train departs from the station, how hot or cold the weather is, how much you weigh, and how tall you are. The value obtained by measuring a quantity is called its magnitude. The magnitude of a quantity is expressed as numbers in its unit.  A measuring unit is a standard quantity used to express a physical quantity. Therefore, to express a measurement we need two things:

1. Magnitude 

2. Unit

For example, your pencil is 30 cm long, here 30 is the magnitude, and the unit in which the length is expressed is 'cm'.  So when you measure length, you compare the unknown length with this known length. 30 centimeters, means the length you have measured is 30 times as much as the known unit centimeter. If your mass is 35 kilograms, it is 35 times as much as the known unit - the kilogram. 

We can measure many different things, but mostly we measure Length, Area, Volume, Mass, Temperature, and Time.

Let us learn about the physical quantities and some of the standard units used to measure them. You can measure things using two different systems: the Metric and the US Standard system.

• The International System of Units (SI), commonly known as the metric system, is the international standard for measurement. In this system, the standard unit of length, mass, and time is meter, kilogram, and second respectively.
• US Standard system of measurement: The four basic units of measurement that are used in the U.S. customary measurement system are inch, foot, yard, and mile.  

Length

Length describes how long a thing is from one end to the other. Length is used to identify the size of the object or the distance from one point to another.

Instruments that we use to measure a length are a ruler, meter scale, and measuring tape.

In the metric system, we measure the length in meters, millimeters, centimeters, and kilometers.
 

Millimeter(mm)	A millimeter is about the thickness of your school ID card or a credit card
Centimeter(cm)	Your fingernail is about one centimeter wide. One centimeter is 10 millimeters long. To measure the length of a study table you use centimeters.
Meter(m)	The length of a Guitar is about one meter long. One meter is 100 centimeters long. To measure the length of a playground you use meters.
Kilometer(km)	We measure the distance between two cities in kilometers. A kilometer is 1000 meters.

Area

The area is the size of a surface: how much is inside the boundary of a flat (2-dimensional) object such as a rectangle, square, triangle, or circle.

For example, the area of a playground with a length of 200 meters and a width of 100 meters is 20000 square meters. We measure the area in square units.

Volume

Volume is the amount of 3-dimensional space an object occupies. Also, called capacity. We measure liquids like water, milk, etc. in milliliters and liters.

Liquid volume is typically measured using specific tools like a graduated cylinder or buret in milliliter(ml) or liter(l).

Milliliter(ml)	1 teaspoon of water makes about 1 milliliter.
Liter(l)	We measure juice, milk in liters. 1 liter is 1000 milliliters.
Kiloliter(kl)	A fire engine carries around 2 kl of water. 1 Kiloliter is 1000 liters.

Mass (Weight)

Mass is how much matter something contains. This bar of chocolate has a mass of 150 grams.

A scale or balance is a device to measure weight or mass.

Gram(g)	A paperclip weighs about one gram.
Kilogram(kg)	One kilogram is 1000 grams. We measure sugar and pulses in kilograms.
Tonne(Tons)	A ton is equal to 1000 kg. A car weighs about 2 tons.

Temperature

Temperature tells how hot or cold a thing is.

Temperature is measured using a thermometer, usually on the Celsius(°C) or Fahrenheit(°F) scale. In metrics, the standard temperature is measured in Kelvin.

To measure temperature we use a thermometer. The red liquid inside the thermometer tells you the temperature.

Celsius(°C)	Water freezes at 0°C and boils at 100°C. This is the most common temperature scale in the world.
Fahrenheit(°F)	This temperature scale is more common in the United States. Water freezes at 32°F and boils at 212°F. To convert Fahrenheit to Celsius, use formula: \(^\circ F = (^\circ C \times 1.8) + 32\)
Kelvin(k)	0 Kelvin or absolute zero is the lowest temperature that any substance can reach. It is the standard temperature unit that is mostly used by scientists.  Kelvin = Celsius + 273.15.

Time

Time is the ongoing sequence of events taking place.

We measure time using seconds, minutes, hours, days, weeks, months, and years. We measure time using clocks, watches, and calendars.

Seconds	It takes about 1 second to ring the doorbell.
Minutes	It takes about one minute to sharpen your pencil or brush your teeth. 1 minute is equal to 60 seconds.
Hours	You play or study for a longer time and measure in hours. One hour is equal to 60 minutes or 3600 seconds.
Day	A day consists of 24 hours. We divide the day into morning, afternoon, evening, and night.

There are a lot of other things we can measure, but these were the most common.

U.S. units of measurement

 

Weight	Pound(lb), Ounce(oz)
Volume	Gallon(gal.), Quart(qt.), Pint(pt.), Cup(c.)
Length	Mile(m.), Yard(yd.), Foot(ft), Inch(in.)