Objective: To learn the English, metric, and SI systems of measurements. The units part of a measurement tells us what scale or standard is being

Transcription

1 Objective: To learn the English, metric, and SI systems of measurements. The units part of a measurement tells us what scale or standard is being used to represent the results of the measurement. The need for common units is necessary so that scientists may have a universal language. 1

2 The English system of units is the system used in the United States and includes inches, feet, miles. The metric system is used internationally and is known as the International System or SI Units. Below are some basic SI Units. Mass kilo kg Length m Time second s Temperature Kelvin K 2

3 Below are the prefixes used for the metric system. 3

4 4

5 Volume is the amount of 3-dimensional space occupied by a substance. If you have a cube that is 1m x 1m x 1m, the volume of this cube would be 1m 3 or 1 cubic. 1 cm 3 = 1 ml ml = 1 L 5

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7 The metric system is based on a base unit that corresponds to a certain kind of measurement Length = Volume = Weight (Mass) = Prefixes plus base units make up the metric system Example: Centi + = Centi Kilo + = Kilo

8 The three prefixes that we will use the most are: kilo centi milli Base Units

9 So if you needed to measure length you would choose as your base unit Length of a tree branch 1.5 s Length of a room 5 s Length of a ball of twine stretched out 25 s

10 But what if you need to measure a longer distance, like from your house to school? Let s say you live approximately 10 miles from school 10 miles = s is a big number, but what if you could add a prefix onto the base unit to make it easier to manage: s = kilos (or 16.1 if rounded to 1 decimal place)

11 These prefixes are based on powers of 10. What does this mean? From each prefix every step is either: 10 times larger or 10 times smaller For example Centis are 10 times larger than millis 1 centi = 10 millis Base Units

12 Centis are 10 times larger than millis so it takes more millis for the same length 1 centi = 10 millis Example not to scale 1 mm 1 mm 1 mm 1 mm 1 mm 1 mm 1 mm 1 mm 1 mm 1 mm cm 41

13 For each step to right, you are multiplying by 10 For example, let s go from a base unit to centi 1 = 10 decis = 100 centis ( 1 x 10 = 10) = (10 x 10 = 100) 2 s = 20 decis = 200 centis (2 x 10 = 20) = (20 x 10 = 200)

14 An easy way to move within the metric system is by moving the decimal point one place for each step desired Example: change s to centis 1 = 10 decis = 100 centis or 1.00 = 10.0 decis = 100. centis

15 Now let s try our previous example from s to kilos: s = decas = hectos = kilos So for every step from the base unit to kilo, we moved the decimal 1 place to the left (the same direction as in the dia below)

16 If you move to the left in the dia, move the decimal to the left If you move to the right in the dia, move the decimal to the right

17 Now let s start from centis and convert to kilos centis = 4 kilos centis = kilos

18 Now let s start from s and convert to kilos 4000 s = 4 kilos Now let s start from centis and convert to s 4000 centis = 40 s

19 Now let s start from s and convert to centis 5 s = 500 centis Now let s start from kilos and convert to s.3 kilos = 300 s

20 Now let s start from kilos and convert to millis 4 kilos = millis or 4 kilos = 40 hectos = 400 decas = 4000 s = decis = centis = millis

21 Summary Base units in the metric system are,, Metric system is based on powers of 10 For conversions within the metric system, each step is 1 decimal place to the right or left Using the dia below, converting to the right, moves the decimal to the right and vice versa