MEASURING SYSTEMS
*No such thing as a “correct” system …and all measuring systems are man-made
· Metrology - the study of measuring systems
· Measuring systems EVOLVE over time
Evolution of Societies
1. Hunter-Gatherers
· Spent most of their time hunting and gathering food
· Did not have or need a measuring system
· Moved from place to place in search of food
2. Agricultural
· Found out how to plant seeds and grow own food
· No longer had to keep moving in search of food
· Grew food and raised animals
· Had lots of children in order to have extra hands to help out on the farm
· With more kids, families had to grow more food
· Sometimes had extra potatoes, but no corn…..so
· They would TRADE with other families
· People began trading pumpkins for corn and corn for potatoes, and potatoes for squash, etc.
· For the first time, people began to TRADE
· For the first time, people needed a measuring system in order to COMMUNICATE
Measuring Systems
· Measuring Systems are a means of COMMUNICATION for TRADE
· Measuring Systems need a STANDARD in order to communicate
· STANDARD = an amount everyone agrees to use for comparison
First Measuring System
· Based on BODY PARTS
· Span – from the outstretched pinky finger to the thumb
· Hand – the measure of the clenched front view of the hand; used to measure the height of horses/animals
· Cubit – elbow to middle finger
· Foot – the length of the foot
· Pace – a step (not sure the size of the step)
Advantages of the Body Parts Standard
1. You always have your tools with you
2. Everyone can relate to the standard
3. Its free
Disadvantages of the Body Parts Standard
1. Everyone has different size body parts and this becomes an enormous problem as TRADE advances
Great Britain
· A world super-power at this time
· Had a huge navy and traded all over the world
· The king wanted to STANDARDIZE measurement systems to avoid getting ripped-off
· He decided to use a stick measured on the length of the distance from the tip of his nose to the end of his fingers on an outstretched hand - he called this a YARDSTICK and insisted that all other countries use it rather than their own measuring systems
· THUS….Great Britain was the FIRST TO USE AN INTERNATIONAL STANDARD
In England-
· The English system was the first international system
· The king took existing units and standardized them. He did NOT invent anything new
· There was the cubit, inch, stone, pint….and dozens more units
· The problem was that all measurement up to now were based on body parts and everyone had different size body parts
· The king steps in with his new yardstick and standardizes measurements
· He made copies of his stick and sold them throughout Europe
English System - all these units already existed
3 tsp = 1 tbs 16 ounces = 1 pound 12 inches = 1 foot
8 ounces – 1 cup 2000 pounds = 1 ton 3 feet = 1 yard
2 Pints = 1 cup 1760 yards = 1 mile
4 quarts – 1 gallon 5280 feet = 1 mile
32.5 gallons = 1 barrell
This English System:
Advantages - universal; that is, it was the same for everyone and people were able to communicate via trade
Disadvantages – too confusing; too cumbersome; NO PATTERN too many units
not reproducible – meaning you can’t make it yourself; can only copy the original)
BIG CHANGES IN MEASUREMENT SYSTEMS
· 1790S – A group of scientists from all over the world meet in France to get rid of the English system
· They decided to find a new system with patterns, with not too many units, and one that could be reproduced
· They erased everything and started from scratch
· They invented a system based (not on the body parts of a dead king) but on the size of the EARTH and the properties of water
· The first unit they came up with was the METER– which is 1/10,000,000 the distance from the equator to the North Pole (meter = Greek for measure
· It was discovered that the distance travelled by a shadow in a certain amount of time = 1 meter
· After the meter stick they made the liter measuring off a box 10cm x 10cm x 10cm and filled it with water
· They called this a liter – they weighed it and called its weight a kilogram
· Now we had the meter to measure length and distance, the liter to measure liquids and the gram to measure mass…BUT what about smaller and much larger units?
· For measurements bigger or smaller that the 3 base units (meter, gram, liter) scientist used prefixes in front of the base units
· And so the Le Systeme Internationale de Unite…a.k.a. SI or Metric System came about
LE SYSTEME INTERNATIONALE DE UNITES…This became the METRIC SYSTEM or the S.I. System
· For measurements of larger and smaller unite the scientists used prefixes in front of the base units
· There are THREE BASE UNITS – the meter, gram, and liter
· As a point of reference, the meter is slightly longer that a yardstick (3 inches longer)
· The gram is about the weight of a medium paper clip
· The liter is about the size of a quart
Note* The system used to this day in the United States is the SAE or Standard American English System
Metric Prefixes:
Kilo 1000
Hector 100
Deca 10
Base 1 gram, meter, liter, volt, joule, curie, etc
Deci .1
Centi .01
Milli .001
CONVERTING METRIC UNITS
K H D M D C M
I E U A A A U I need 2.3 L of acid, but I only have a 100mL
N N N N N K F graduated cylinder. How many mL is 2.5 L?
G R K Y I E F 2.5 L = 2,500 mL
Y S S S I
H N
S
Metric Conversions
4 Steps
1. Write the prefixes in order (K H D M D C M)
2. Determine the direction ( left or right )
3. Count how many units you move
4. Move the decimal
THE UNITS
_Prefix Name Abbreviation Value______
METER
Kilo Kilometer km 1000 meters
Hecto Hectometer hm 100 meters
Deca Decameter dam 10 meters
Meter (base unit) METER m 1 meter
Deci Decimeter dm 1/10 (0.1) of a meter
Centi Centimeter cm 1/100 (0.01 of a meter
Mille Millimeter mm 1/100 (0.001) of a meter
GRAM
Kilo Kilogram kg 1000 grams
Hecto Hectogram hg 100 grams
Deca Decagram dag 10 gram
Gram (base) GRAM g 1 gram
Deci Decigram dg 1/10 (0.1) of a gram
Centi Centigram cg 1/100 (0.01) of a gram
Milli Milligram mg /1000 (0.001) of a gram
LITER
Kilo Kiloliter kL 1000 liters
Hecto Hectoliter hL 100 liters
Deca Decaliter daL 10 liters
Liter (base) LITER L 1 liter
Deca Deciliter dL 1/10 (0.1) of a liter
Centi Centiliter cL 1/100 (0.01) of a liter
Milli Milliliter mL 1/1000 (0.001) of a liter