Units of Measurement

Units of MeasurementBySuwat Niyomthai

Units of Measurement• In Measurement we talk about \"Units\" ... what are they?A unit is any measurement that there is 1 of.So 1 meter is a unit.And 1 second is also a unitAnd 1 m/s (one meter per second) is also a unit,because there is one of it.

• Without the \"1\"• It is also common to drop the \"1\" in front and just talk about the type of measurement as a unit.stopwatch• Example: a commonly used unit of time is the second• We don't say a stopwatch measures \"1 seconds\", we say it measures \"seconds\".

• So \"Unit\" is a general term that means the type of measurement. And people understand that we mean just \"1\" of it.• So a conversation might go like thisAlex: \"It measures 100\"Sam: \"In what Unit?\"Alex: \"Centimeters\"

Example: Speedometer• Speedometer• What unit does this Speedometer measure?• It measures km/h (kilometers per hour)• So \"220\" means 220 kilometers per hour.

Abbreviation• We usually write units just using their abbreviations.• Example: km for kilometer• Example: m/s (or m s-1) for meter per second• m/s is a unit of speed• Example: kg/m3 (or kg m-3) for kilogram per cubic meter• kg/m3 is a unit of density: how much mass per unit of volume.

Standardized • Units of Measurement are \"standardized\", meaning that there is a well-defined standard way to measure 1 of them. • metre bar • Example: For many years (1889 to 1960) there was the International Prototype Metre bar to show people exactly what 1 meter was. • But that wasn't accurate enough! • Now \"1 Meter\" is defined as how far light travels in 1/299,792,458 of a second.

Different Systems of Measurement• Units can be grouped together to make a \"System\".• Example: the meter, kilogram and second (together with a few other units) together make up the \"SI\" Metric System of Measurement.• Example: the inch, foot, yard and mile are the units of length in the US Standard System of Measurement

Unit Price • Unit Price tells us the cost per liter, per kilogram, per pound, etc, of what we want to buy. • It is a good way of comparing costs of what we buy. • Example: What is best • 2 liters of Milk at $3.80, or • 1.5 liters of Milk at $2.70 ? • In this case the \"Unit\" is 1 liter, and the Unit Prices are: • $3.80 / 2 liters = $1.90 per liter • $2.70 / 1.5 liters = $1.80 per liter • So the lowest Unit Price (and the best bargain) is 1.5 liter at $2.70.

Exercise