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Units of Measurement
Why they are important...
....like $125,000,000 important!
In 1999 NASA’s $125,000,000 Mars Climate Orbiterspace probe entered the Martian atmosphere burstinto flames and crash landed. It was entirelydestroyed.
A committee was formed to investigate the crash.
They found that...
...the crash stemmed from a miscommunication between the probes manufacturer and the navigational team regarding units...
o Lockheed Martin used English Units (inches, feet, pounds)o The Navigation Team used Metric Units (Meters, Newtons)
“This is going to be the cautionary tale that will be embedded into
introduction to the metric system in elementary school, high school, and college science courses till the
end of time.”
English Standard Units
• You are probably familiar with these, they include:
• Inches• Feet• Yard• Mile• Pounds• Cup
But there is a problem...
What’s the problem?
The USA is the only major country in the world that still uses English Standard Units.
The Metric System
• The rest of the world uses it.• In the United States the Metric System is used by:
• Scientists• Doctors• Engineers• Anyone who works with international clients
• Basically metric units are used for everything except day-to-day life in America.
• Also known as SI or Systeme Internationale Units
There is good news though...
... so prepare your best happy dance!
The Metric System Is Easy!
• The Metric System is based upon Powers of 10.– 1000 Millimeters in 1 Meter– 10 Millimeters in 1 Centimeter– 100 Centimeters in 1 Meter– 1000 Meters in 1 Kilometer
But what about English Standard units?
• Unlike Metric units English Standard units are based on complete randomness.– They are so strange they
probably weren’t evendeveloped by a scientist but rather a creepy guy in a van.
Not really but it was way funnier that way!
Seriously though, you’ll like the metric system if you give it a chance!
Base Units
• The metric system uses certain fundamental Base Units:• Length = Meters•Mass = Kilogram• Volume = Liter• Time = Second• Temperature = Degrees Kelvin
Metric Units
Time: Unit Seconds: defined as time for acertain excited atom (cesium) to make aspecified number of oscillations.
Length: Unit Meters: defined as distance lighttravels in a specified fraction of a second.
Metric Units
One cubic meter is 1,000 liters.
One cubic meter of water has a mass of 1,000kg, one metric ton, about 2,200 lbs.
Mass: Unit Kilogram: defined as the mass of a chunk of platinum in Paris, shown here.
Volume: Unit Liter: defined as the mass of 1 Kilogram of water.
Metric Prefixes
If you need a larger or smaller unit, one can be created by adding a prefix.
Learning Check
A rattlesnake is 2.44 m long. How long is the snake in cm?
a) 2440 cmb) 244 cmc) 24.4 cm
English and SI Conversions
• If you know ONE conversion for each type of measurement, you can convert anything!
• You must memorize and use these conversions:–Mass: 454 grams = 1 pound– Length: 2.54 cm = 1 inch–Volume: 0.946 L = 1 quart
Learning Check
A rider on RAGBRAI averages 18 miles per hour what is their speed in kilometers per hour?