The Metric System. What the heck is it? How do you use it?

Transcription

1 The Metric System What the heck is it? How do you use it?

2 We, in the USA feel this way about the metric system:

3 Every country in the world uses the metric system although many products are still manufactured in common sizes for public use. The metric system was devised by French scientists in the late 18th century to replace the chaotic collection of units then in use. The goal of this effort was to produce a system that did not rely on a miscellany of separate standards, and to use the decimal system rather than fractions.

4 To obtain a standard of length a quadrant of the earth (one-fourth of a circumference) was surveyed from Dunquerque, in France, to Barcelona, in Spain along the meridian that passes through Paris. This distance, from the North Pole to the equator, was divided into ten million parts to constitute the meter (spelled metre in some countries).

5 The definition of the meter - has become more and more precise through the years since, even though its length has not changed. Currently the meter is the distance light travels in a vacuum in 1/ second.

6 On April 5, 1893 the inch was redefined as precisely 1/39.37 meter, and in a very real sense we have been using the metric system ever since. In 1959 the length of the inch was shortened slightly to its present definition of centimeters.

7 The speed of light, a universal constant, is almost exactly 300 megameters per second. The circumference of the earth is 40 megameters (by the original definition of the meter in the eighteenth century).

8 Which other countries, besides the U.S., do not use the metric system? According to a survey taken by USMA many years ago, the only other countries that have not officially adopted the metric system are Liberia (in western Africa) and Burma (also known as Myanmar, in Southeast Asia).

9 Most other countries have either used the metric system for many years, or have adopted it in the last 30 or 40 years. Metrication is a process that does not happen all at once, but is rather an evolutionary process that happens over time. Among countries with non-metric usage the U.S. is the only significant holdout.

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11 Metrication in the British Commonwealth In the 1970s, most British Commonwealth nations changed over from the Imperial system of units to the metric system. Several of these nations rapidly and successfully made the metric transition, thanks to strong government encouragement and support.

12 The Metric Roots Meter Measures Length. Liter Measures Volume. Gram Measures Mass.

13 Reading a Metric Ruler Metric side will be labeled EITHER cm or mm. For each centimeter, there are 10 millimeter lines in between.

14 Using an Electronic Balance Before weighing anything on a balance, it needs to be "tared," or zeroed to read 0.00 g. Place a weighing boat on the balance and zero it again. Pour out the substance to be measured until the scale displays the desired amount.

15 Reading a Graduated Cylinder Graduated cylinders typically measure using the unit of milliliters. Liquid molecules stick to the side of a graduated cylinder causing the liquid to make a dip called the meniscus. To correctly read the volume, look at the bottom part of the meniscus.

16 Abbreviations: METER = m LITER = l GRAM = g milli = m centi = c deci = d deka = dk hecto = h kilo = k

17 Beyond k and m. The metric scale of measurements is much larger than just six prefixes. It extends well beyond kilo on the upper end and milli on the lower end.

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19 Metric Prefixes:

20 Making the Decimal Bounce.

21 Scientific Notation

22 Scientific Notation A short-hand way of writing large numbers without writing all of the zeros.

23 The Distance From the Sun to the Earth 93,000,000

24 Step 1 Move decimal left Leave only one number in front of decimal

25 Step 2 Write number without zeros

26 Step 3 Count how many places you moved decimal Make that your power of ten

27 The power of ten is 7 because the decimal moved 7 places.

28 93,000, Standard Form 9.3 x Scientific Notation

29 Practice Problem Write in scientific notation. Decide the power of ten. 1) 98,500,000 = 9.85 x 10? 2) 64,100,000,000 = 6.41 x 10? 3) 279,000,000 = 2.79 x 10? 4) 4,200,000 = 4.2 x 10? 9.85 x x x x 10 6

30 More Practice Problems On these, decide where the decimal will be moved. 1) 734,000,000 = x ) 870,000,000,000 = x ) 90,000,000,000 = x ) 7.34 x ) 8.7 x ) 9 x 10 10

31 Complete Practice Problems Write in scientific notation. 1) 50,000 2) 7,200,000 3) 802,000,000,000 1) 5 x ) 7.2 x ) 8.02 x 10 11

32 Scientific Notation to Standard Form Move the decimal to the right 3.4 x 10 5 in scientific notation move the decimal 340,000 in standard form

33 Do you recognize this number, kg.? This is the mass of a dust particle! It can be writtien with Scientific notation too

34 The answer would be: kg X kg

35 Write in Standard Form 6.27 x ,270, x ,100