1. Weight and Mass Section 9.5

2. 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. 2 Martin-Gay, Prealgebra, 5ed

3. U.S. Units of Weight Unit Fractions 16 ounces (oz)  1 pound (lb) 2000 pounds  1 ton The U.S. system of measurement uses the ounce, pound, and ton to measure weight. 3 Martin-Gay, Prealgebra, 5ed

4. 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. Mass 4 Martin-Gay, Prealgebra, 5ed

5. 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 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. 5 Martin-Gay, Prealgebra, 5ed

6. The prefixes for units of mass in the metric system are the same as for units of length. Metric System of Measurement Prefix kilo hecto deka deci centi milli Meaning 1000 100 10 1/10 1/100 1/1000 1 milligram (mg)  1/1000 or 0.001 g 1 centigram (cg)  1/100 or 0.01 g 1 decigram (dg)  1/10 or 0.1 g 1 gram (g)  1 g 1 dekagram (dag)  10 g 1 hectogram (hg)  100 g 1 kilogram (kg)  1000 grams (g) Metric Unit of Length 6 Martin-Gay, Prealgebra, 5ed

7. 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. kg hg dag g dg cg mg StartEnd 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 7