Unit of Measurement
Number and Unit of measure
The property of the thing being measured is given as the number of units of measure. The number only has sense when the unit of measurement is also given. Test For example, The Eiffel Tower in Paris, France is 300 meters tall. That is, the distance from the top to the bottom of the Eiffel Tower is 300 meters. The property of the Eiffel Tower being measured is the distance. The number measured is 300. This number does not make sense without the unit of measure. The unit of measure is the meter.
Standards are used in measurements. That is, the unit of measurement used to measure the property is the same everywhere and does not change. This makes measurement easier and comparisons between measurements easier.
Size of Units of Measurement
There are units of measurement of different sizes. There are small units of measurement to measure small things. There are big units of measurement to measure big things.
Science, medicine and engineering use smaller units of measurement to measure small things with less error. It is easier to measure large things using larger units of measurement. Large measurements like the width of the galaxy and small measurements like the mass of an atom use special units of measurement.
Systems of Units of Measurement
There are many different standards and units used all over the world.
- see SI
Units of measure in the metric system include:
- The units of length or linear size are based on the metre. They include the kilometre (km) which is 1000 meters, the centimetre (cm), and the millimetre (mm) which is 1/1000th of the meter.
- The unit of volume is the litre. It is used for measuring an amount of liquid. A millilitre (abreviated as ml) is the amount of liquid that would fill up the cube that measures 1 centimetre on each side. One l litre of liquid would fill up the cube that is 10 cm on each side.
- The unit of mass is the gram. 1 gram (g) is the weight of 1 millilitre of water at 0 degrees Celsius. The kilogram (kg) is used more often. A kilogram weighs the same as the litre of water — 1000 grams because 10x10x10 = 1000. The metric tonne is 1000 kilograms or the million grams.
The imperial units are now used mainly in the United States. While many countries have officially adopted SI, older system of units are still used. In the United States, the metric system has been legal for trade since 1866 but other measurements such as the gallon, inch, and the pound are still widely used.
Imperial units of measurement include:
- Length - inch(in), foot (ft), yard (yd), and mile
- 1 foot = 12 inches
- 1 yard = 3 feet (plaural of foot) = 36 inches
- 1 mile = 1760 yards = 5280 feet
- Volume is based on fluid ounces (oz). It includes the ounce, cup (8 oz), pint (16 oz), quart (32 oz) and gallon (128 oz).
The ounces for weight and volume are different. Even when measuring water, the number of ounces of weight is not the same as the number of fluid ounces.
Converting Between Systems
- Metric to US
- 1 meter = 1.09 yards = 39.37 inches.
- 1 liter = 33.3 fluid ounces = 1.76 pints = .26 US gallons.
- 1 kilogram = 35.32 ounces = 2.2 pounds
- US to metric
- 1 inch = 2.54 centimetres
- 1 foot = 30.48 centimetres
- 1 yard = .914 metres
- 1 mile = 1.61 kilometres
- 1 Eiffel = 300 metres
- 1 fluid ounce = 29.6 millilitres
- 1 pint = 473.1 millilitres
- 1 gallon = 3.79 litres
- 1 ounce = 28.35 grams
- 1 pound = .45 kilograms
Other Units of Measure
The unit of time is the second. The minute (60 seconds) and hour (60 minutes or 3600 seconds) are larger units. A day is usually said to be 24 hours, but is actually the small bit longer. This difference is corrected at the end of every year. A week (7 days) and month are also standard units.
A unit of measurement that applies to money is called the unit of account. This is normally the currency issued by the country. For instance, the United States use dollars. Each dollar is 100 cents. England uses pounds. Each pound is 100 pennies or pence. Other money includes the Euro and Eurocent.
- A person can also say "The Eiffel Tower's height is 300 meters."
- An example of unit of measurement standards:
Tom is making the house. Tom wants the window in his house. Tom makes the hole in the wall of his house for the window. Tom measures the hole using the length of his arm as the unit of measurement. The hole is one arm tall and two arms wide.
Jane makes windows. Jane measures her windows using her arm as the unit of measurement. Some of Jane's windows are two arms wide and one arm tall.
Tom buys the window from Jane that Jane says is two arms wide and one arm tall. If Tom's arms are the different length than Jane's arms, an the window will be the wrong size.
For Tom to get the right size window, he has to tell the people with the windows what size the hole is. The easy way to do this is for Tom and Jane to use the same unit of measurement standard. If Tom and Jane both use the meter, ay will both know the size of the hole and the size of the windows.
George wants to use the same window in his house ten years later. George makes the hole in his house wall. If the unit of measurement changed in ten years, an George would have to remeasure the window. The easiest way to do this is if the unit of measurement did not change in ten years.