Metric System. Basic Skills

Transcription

1 Metric System Basic Skills

2 Systéme International The metric system is an international decimalized system of measurement created in France in 1791 during the French Revolution. Since the 1960s the International System of Units ("Système International d'unités" in French) has been the internationally recognized standard metric system. This system is commonly called the SI system. The SI or metric system is widely used around the world for personal, commercial, and scientific purposes. 2

3 Systéme International Name Symbol Quantity meter m length kilogram kg mass second s time Ampere A electric current Kelvin K thermodynamic temperature candela cd luminous intensity mole mol amount of substance 3

4 Length, Mass, Time Length (m): defined as the distance traveled by light in a vacuum during a tiny fraction of time. Mass (kg): defined by an International Prototype Kilogram made of a platinum-iridium alloy and stored in a vault in Sèvres, France. Time (s): defined as the duration of periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom. 4

5 Standard Prefixes for SI Units Prefix Symbol Factor Factor as Exponent peta P = tera T = giga G = 10 9 mega M = 10 6 kilo k = 10 3 hecto h 100 = 10 2 deca da 10 = 10 1 deci d 0.1 = 10-1 centi c 0.01 = 10-2 milli m = 10-3 micro µ = 10-6 nano n = 10-9 pico p = femto f =

6 Prefix: kilo kilo represents a factor of So a kilometer is 1000 meters, a kilogram is 1000 grams, &etc. Use kilometers to measure longer distances. 1 kilometer is miles. Have you every run a 10K race? How far is a 5K run? When we do problems, we will generally want to convert distances/lengths into meters. To convert kilometers to meters multiply by 1000 (or move the decimal 3 places to the right). To convert meters to kilometers divide by 1000 (or move the decimal 3 places to the left). Think: in any given distance, there are more meters than there are kilometers (just like there would be more inches than feet!) 6

7 Prefix: kilo (practice) Convert into meters: o 4 kilometers = 4,000 meters o 3.5 km = 3,500 meters o 0.45 km = 450 meters Convert into kilometers: o 1200 meters = 1.2 kilometers o 11,000 m = 11 kilometers o 750 m = 0.75 kilometers 7

8 Prefix: milli milli represents a factor of 1/1000th. So a millimeter is 1/1000 th of a meter, a millisecond is 1/1000 th of a second, &etc. Use millimeters to measure small lengths. 1 millimeter is about the thickness of your finger nail When we do problems, we will generally want to convert distances/lengths into meters. To convert millimeters to meters divide by 1000 (or move the decimal 3 places to the left). To convert meters to millimeters multiply by 1000 (or move the decimal 3 places to the right). Think: in any given length, there are more millimeters than there are meters (just like there would be more inches than feet!) 8

9 Prefix: milli (practice) Convert into meters: o 5 millimeters = meters o 340 mm = meters o 16.5 mm = meters Convert into millimeters: o 1.0 meters = 1000 millimeters o 0.88 m = 880 millimeters o m = 3 millimeters 9

10 Prefix: centi centi represents a factor of 1/100th. So a centimeter is 1/100 th of a meter, a centigram is 1/100 th of a gram, &etc. Use centimeters to measure small lengths. 1 centimeter is about the width of your finger nail. 1 inch = 2.54 centimeters. When we do problems, we will generally want to convert distances/lengths into meters. To convert centimeters to meters divide by 100 (or move the decimal 2 places to the left). To convert meters to centimeters multiply by 100 (or move the decimal 2 places to the right). Think: how many cents are there is a dollar? How many centimeters is a meter? How do you write 25 cents as a dollar amount? Isn t it $0.25? It s the same for centimeters! 10

11 Prefix: centi (practice) Convert into meters: o 25 centimeters = 0.25 meters o 165 cm = 1.65 meters o 1.5 cm = meters Convert into centimeters: o 1.0 meters = 100 centimeters o 0.78 m = 78 centimeters o 0.06 m = 6 centimeters 11

12 Converting Centimeters & Millimeters 10 millimeters = 1 centimeter A meter stick has 100 centimeter marks, and 1000 little tick marks for millimeters. Think: since a millimeter is smaller than a centimeter, there will be more millimeters in any given length than there are centimeters! How long is the paper clip? About 2.1 centimeters, but 21 millimeters! 12

13 Centimeter and Inch Rulers 13

14 Area & Volume Area is a two dimensional concept (length x length). In the metric system, area is measured in m 2 (square meters) Volume is a three dimensional concept (length x length x length). In the metric system, volume is measured in m 3 (cubic meters). We also use liters in the metric system. 1 m 3 = 1000 liters! What is the length of the longest side, surface area of the top, and the volume? 14