Introduction to the Metric System

Goals

• Identify the basic units of measurement in the metric system
• Give approximate conversion factors to the US Customary System
• State selected SI prefixes, their values and meaning
• Convert measurements to their proper units.
• Solve simple problems involving measurement in the metric system

Discussion

• The metric system or Systeme international d'unites (SI) is the standard for measurement in most of the world.
• Developed during the French revolution
• It is based on the decimal system
• The basic units are
  • The Meter (m), which was based on the distance from the north pole to the equator, and is about 1 yard.
  • The Gram (g), for mass 1000 grams (or 1 kilogram kg) are about 2.2 pounds
  • The Liter (l) , for liquid volume, 1 l is about 1 quart
  • Temperature is measured in Celsius (C)
    • Water freezes at 0 degrees C
    • Water boils at 100 degrees C
• In the US Customary system, we have complex grouping of units
  • 1 yard = 3 feet = 36 inches , miles, rods, furlongs, ...
  • 8 pints = 4 quarts = 1 gallon
• In the metric system grouping is done in powers of ten
• 1 kilogram (kg) = 10 hectograms (hg) = 100 dekagrams (dag) = 1000 grams
• 1 kiloliter = 10 hectoliters = 100 dekaliters = 1000 liters.
• 1 kilometer = 10 hectometers = 100 dekameters = 1000 meters.

• Prefix	Symbol	Meaning
  kilo	k	1000 x base
  hecto	h	100 x base
  deka	da	10 x base
  -		base
  deci	d	.1 x base
  centi	c	.01 x base
  milli	m	.001 x base

  (See pages 434 - 435)
• Conversions in the metric system are quite easy
• Example 1: Convert 200 grams to kilograms

  From the above table we have 1 kilogram = 1000 grams, so:
  
       200 grams      1 kilogram      200 
       ---         x ------------ = ------  kilograms = .2 kilograms
        1             1000 grams     10000
  
  You could also just count the units we are moving and change the 0
  We are moving up the chart  3 steps, so we move the decimal
  point to the left three times
       200 grams = 20 dekagrams = 2 hectograms = .2 kilograms 
      

Examples

• Example 2: (number 58)

  Which walk is faster?
  Plan:
     Convert to a common unit, compare
     Use meters as the common unit
  
     1 dam =  10 m
     1 hm = 100 m
  
     10m/10 min  = 1m/min
     100m/10 min = 10m/min
     10m/min is much faster than 1m/min, so 1 hm/10 min is faster
      

• Example 3: (number 60)

         Which is larger? 5kg or 15 lb
         Plan: Convert to a common  unit
         We know 1 kg is about 2.2. lb,
         Conver to kg
       
          15         1 kg
         ----  lb x ------ = 15/2.2 kg = 6.82 kg
          1         2.2 lb
    
        So 15 pounds is more than 5 kg.
  
      

Homework