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Conversions: aka Dimensional Analysis. The Metric System. In America, we use the standard system of units (pounds, ounces, miles, feet, etc) In Science, and in all other countries, a different system is used called the metric system. The Metric System.
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The Metric System • In America, we use the standard system of units • (pounds, ounces, miles, feet, etc) • In Science, and in all other countries, a different system is used called the metric system.
The Metric System • The U.S. will probably switch to it in your lifetimes because: • U.S. is the ONLY major nation not using it. • Easier trade and communication • It is a decimal system (like our money) and much easier to use.
Metric VS Standard • Neither is more ACCURATE, just different.
Standard System • 88 different types of units • hundreds of conversions.
Metric System • Only 3 base units • 10 standard prefixes • Only one set of conversions to learn. The one set works for everything.
Metric Base Units • Length • Meters (m) • Mass – (weight) • Grams (g) • Volume • Liters (L)
Tera T 1012 Giga G 109 Mega M 106 Kilo k 103 (Fill in your chart) deci d 10-1 centi c 10-2 milli m 10-3 micro μ 10-6 nano n 10-9 pico p 10-12 Metric Prefixes
Conversions • How many minutes are in 3 hours? • 180 minutes! • Many of you knew can do this in your head, instinctively. • To get the answer, you used a CONVERSION FACTOR (60 min = 1 hour.)
Conversions • How about a harder one? How many minutes are in 4.597 hours? • Since you can’t do this in your head, you must think and use the same method you used before. • 275.8 minutes
Dimensional Analysis • Convert 14.3 cm to meters: • 14.3 cm |________ • l • Write your t bar and add the given with its label.
Dimensional Analysis • Convert 14.3 cm to meters: • 14.3 cm |________ • l cm • Add the units given on the t bar so that they will cancel out.
Dimensional Analysis • Convert 14.3 cm to meters: • 14.3 cm |______m_ • l cm • Add the units you are trying to get to.
Dimensional Analysis • Convert 14.3 cm to meters: • 14.3 cm |___1 ___m_ • l 100 cm • Fill in the conversion.
Dimensional Analysis • Convert 14.3 cm to meters: • 14.3 -cm- |___1 ___m_ = • l 100 -cm- • Cancel units and do the math. • 14.3 x 1 ÷ 100 = .143 m
Dimensional Analysis • There are some cases that have special rules: • Multiple steps • Units in the denominator
Multiple Steps • If it takes 2 or more conversions. (Folders!) • g in 3.1 lbs? 1 lb = 16 oz; • 1 oz = 0.0353 g • 3.1 –lbs- l 16 –oz- l 0.0353 g = ? • l 1 -lb- l 1 –oz- • ( 3 x 16 x 0.0353 ) = 1.75 = 1.8 g
Units “per” (Miles per hour) • If you read a unit “per ____”, then it goes on the bottom (denominator.) • Its conversion goes UP and across, so you can cancel. 35 mil l 1 hr l 1 min = ? hr l 60 min l 60 sec (35 ÷ 60 ÷ 60 ) = 0.09722222 = 0.097 miles per sec