PHYSICAL SCIENCE A NOTES

MEASUREMENT BASICS

In the past, other things were used to measure:

forearms hands
feet stones
sticks fabric/string
seeds
 fingers
Anything can be used to measure.  But standards of measurement are better!

What are standards?

  • They are exact (the same size) all the time [unlike arms and feet]
  • They are not estimates
  • Everyone agrees what they are (such as inches and meters)
  • They make communication and comparison easy
In our world today, there are two standards:
1. SI ("the metric system")
2. American units (English, standard)
American Units
      Examples:
       
      • feet
      • inches
      • cups
      • pounds
      • miles
      • °F
      • ounces
      • gallons

      Benefits (positives) of American units:

      • Americans use them and already know how to use them (are familiar with them)
      • Based on measurements needed in everyday life (it's practical)
      Drawbacks (negatives) of American units:
      • Only used in U.S. (not world-wide)
      • Lots of conversion factors to remember (makes converting to other units harder)
      • Uses fractions
      • Hard to measure very small things
 SI
- stands for "System International"
- often called "the metric system"
 Examples:
    • meter
    • kilogram
    • liter
    • Newton
    • °C
    • centimeter
    • grams
    • milliliter

    Benefits (positives) of SI units:

    • Easy to convert between units (whole system is based on the number 10)
    • No fractions (uses decimals)
    • Easier to measure very small things
    • Used throughout the world
    • Units that all scientists use
    Drawbacks (negatives) of SI units:
    • Americans don't know them well (so it would take a lot of time/effort to learn them)