The Metric System

2. The Metric System ---The Universal Language of Measurement--- • Metric System – scientists & engineers use this language to communicate • The metric system is often referred to as the International System (“SI”) of Units • The metric system is based on the number 10 and multiples of 10.

3. Metric Quantities • We will encounter a number of (base) metric quantities through the course of this class. • For now we will just focus on two: • Length • Mass

4. LengthThe distance between two points • Meter (m) – the basic unit of length in the metric system If it is not appropriate to measure something in meters we can use metric prefixes to describe quantities that are larger or smaller than a meter. • Example if something is smaller we can use the centimeter • Centimeter (cm) – one hundredth of a meter 1 cm = 1/100 m = 0.01 m 100 cm = 1 m • Example: if something is bigger we can use the kilometer: Kilometer – one thousand meters 1 km = 1000m 1 m = 1/1000 km

5. Massa measure of the amount of matter in an object • Kilogram (kg) – the basic unit of mass in the SI system • Example if something is smaller we can use the gram (which is at the base of the scale, but is not the “base unit” of mass). • Gram(g) – one thousandth of a kilogram 1 g = 1/1000 kg = 0.001 kg 1000 g = 1 kg • Example: if something is smaller still, then we can use a different prefix. • Milligram (mg)– one thousandth of a gram 1 mg = 1/1000 g = 0.001 g 1000 mg = 1 g

6. Metric Prefixes • The metric prefixes all have a mathematical meaning. If you know the meaning of each prefix then it is VERY easy to convert from one unit to the other. • Many of you have memorized some mnemonic for the metric prefixes (“King Henry…”) – FORGET THIS …IT IS CRAP! • Memorizing this does NOT mean that you know it, understand it, and can work with it. • Actually, students who use this are often the ones that make the most mistakes.

7. Metric Prefixes

8. Metric Prefixes(same info in a different manner) Example: Convert 25cm to meters using dimensional analysis.

9. Solution Convert 25cm to meters using dimensional analysis. Set up a conversion fraction so that the units that you have will cancel out. Put the appropriate values in the fraction and do the math. You’ll get the right answer every time without worrying, “oh, do I move the decimal to the right or to the left.” JUST DO THE MATH!!!!!

10. Know the METRIC SYSTEM and use DIMENSIONAL ANALYSIS…it’s easy! Trust me, this class will be hard enough…don’t make it worse.