2.1
• A standard of measurement is an exact quantity that people agree
to use as a basis of comparison.
• When a standard of measurement is established, all measurements are
compared to the exact same quantity - the standard.
• In SI (the metric system), prefixes are used to make the base units
larger or smaller by powers of ten. The most common prefixes are:
kilo- ... 1000 times
deci- ... one tenth
centi- ... one hundredth
milli- ... one thousandth
micro- ... one millionth
nano- ... one billiionth
2.2
• The most commonly used SI units are: length=meter, volume=liter (cubic
decimeter), mass=kilogram, time=second, temperature=Kelvin.
• Any SI unit can be converted to any other related SI unit by multiplying
or dividing by the appropriate multiple of ten.
• Density is the mass per unit volume of a material.
• Zero degrees Kelvin is absolute zero. 273 degrees Kelvin is
0 degrees Celsius ... the freezing point of water. So, K=C+273.
2.3
• Graphs are visual displays of information or data.
• Line graphs show continuous changes between related variables.
Bar graphs are used toshow data collected by counting. Circle or
pie graphs show how a fixed quantity can be broken into parts.
• In a line graph, the independent variable is always plotted on the
horizontal x-axis; the dependent variable is always plotted on the vertical
y-axis.
2.4
• There are many benefits and drawbacks to the adoption of SI.
• SI units are already in wide use on consumer goods in the U.S. |