Transcript Standards of Measurement - Lincoln Elementary School

Standards of Measurement
The International System of Units
(SI)
Units and Standards
• In order for a measurement to be useful, a
measurement standard must be used.
• A standard is an exact quantity that people
agree to use for comparison.
Measurement Systems
Suppose the length of a
string in a ball of yarn is
100. Can you tell how
much string is in the ball?
NO!!
• It could be 150 feet, 150 meters, or some
unit you’ve never heard of.
• In order for a measurement to make sense
it must have a number and a unit.
International System of Units
• In the U.S. we buy milk by the gallon, potatoes
by the pound, and lumber by the foot.
• These are a part of the English system of
measurement.
• Most other nations use a system of
measurement based on multiples of ten.
• This is known as the International System of
Units or SI.
Common SI Prefixes
Prefix
Symbol
Multiplying Factor
Kilo-
k
1000
Deci-
d
0.1
Centi-
c
0.01
Milli-
m
0.001
Micro-
m
0.000001
Nano-
n
0.000000001
Using SI Units
• Every type of quantity measured in SI
has a base unit and a symbol for that
unit.
SI Base Units
Quantity Measured
Unit
Symbol
Length
Meter
m
Mass
Kilogram
kg
Time
Second
s
Electric current
Ampere
A
Temperature
Kelvin
K
Amount of
substance
Mole
mol
Intensity of light
Candela
cd
Length
• The SI base unit for length is the meter (m).
• Remember: SI is based on powers of ten
• Therefore:
1m=10dm=100cm=1000mm
• Metric rulers and meter sticks are used to
measure length.
Choosing a Unit
• The size of the unit you use to measure with
will depend on the size of the item being
measured.
1 meter
10 football fields=
1 kilometer
1
centimeter
Volume
• The amount of space occupied by an object.
• Volume= length x width x height
3 cm
3 cm
• V= 3cm x 3cm x3cm
• V= 27cm 3
3cm
Mass
• Measurement of the matter in an object.
• Base unit: kilograms (kg)
• Grams (g) and milligrams (mg) are used for
measuring objects of small mass.
Which ball has
more mass?
Density
• Density is the mass per unit of volume of a
material. (Expressed as grams per cubic cm)
• D=m/v
A cube of silver would be more dense than a cube of
aluminum, even if they were the same size!!
Time and Temperature
• The SI unit for time is the second (s).
• The SI unit for temperature is the Kelvin (K).
• 0 degrees K is the COLDEST possible
temperature, also known as absolute zero.
That is -273 degrees Celsius,
which is 273 degrees below
freezing!!
Summary
• A standard is an exact quantity that people agree to use for comparison.
• In order for a measurement to make sense it must have a number and a
unit.
• The International System of Units or SI is a system of measurement based
on units of 10 and used by most nations around the world.
• Every type of quantity measured in SI has a base unit and a symbol for
that unit.
• The SI base unit for length is the meter (m).
• The size of the unit you use to measure with will depend on the size of the
item being measured.
• Volume= length x width x height
• Mass is the measurement of the matter in an object (kg).
• Density is the mass per unit of volume of a material. (Expressed as grams
per cubic cm)
• The SI unit for time is the second (s).
• The SI unit for temperature is the Kelvin (K).