Transcript Chapter 9: Geometry and Measurement

Section 9.5
Weight and Mass
Whenever we talk about how heavy an
object is, we are concerned with the
object’s weight. We discuss weight when
we refer to a 12-ounce box of cereal, an
overweight 19-pound tabby cat, or a
barge hauling 24 tons of garbage.
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The U.S. system of measurement uses the
ounce, pound, and ton to measure weight.
U.S. Units of Weight
16 ounces (oz) = 1 pound (lb)
2000 pounds = 1 ton
Unit Fractions
16 oz
1lb
=
=1
1lb
16 oz
2000 lb
1 ton
=
=1
1 ton
2000 lb
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Mass
In scientific and technical areas, a careful
distinction is made between weight and mass.
Weight is really a measure of the pull of
gravity. The farther from Earth an object gets,
the less it weighs. Mass is a measure of the
amount of substance in the object and does
not change. Astronauts orbiting Earth weigh
much less than they weigh on Earth, but they
have the same mass in orbit as they do on
Earth.
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The basic unit of mass in the metric system is the
gram. It is defined as the mass of water contained
in a cube 1 centimeter (cm) on each side.
1 cm
1 cm
1 cm
A tablet contains 200 milligrams of ibuprofen.
A large paper clip weighs approximately 1 gram.
A box of crackers weighs 453 grams.
A kilogram is slightly over 2 pounds.
An adult woman may weigh 60 kilograms.
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The prefixes for units of mass in the metric
system are the same as for units of length.
Metric System of Measurement
Prefix Meaning
Metric Unit of Length
kilo
1000
1 kilogram (kg) = 1000 grams (g)
1 hectogram (hg) = 100 g
hecto
100
1 dekagram (dag) = 10 g
deka
10
1 gram (g) = 1 g
deci
1/10
1 decigram (dg) = 1/10 or 0.1 g
centi
1/100
1 centigram (cg) = 1/100 or 0.01 g
1 milligram (mg) = 1/1000 or 0.001 g
milli
1/1000
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The three most commonly used units of
mass in the metric system are the
milligram, the gram, and the kilogram.
As with length, all units of mass are powers of 10
of the gram, so converting from one unit of mass
to another only involves moving the decimal point.
End
kg
hg
dag
g
Start
dg
cg
mg
2 units to the left
Using the listing of units of mass, convert 4.75 cg to
grams.
04.75 cg = 0.0475 g
2 places to the left
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