Measurement and SI Units

1
Measurement and SI Units

• Section 1-3 in text

2
Using Scientific Notation

• A. Scientists often work with very large or very
  small numbers.
• 1. Speed of light 300,000,000 meters per
  second
• 2. Speed of snail 0.00086 meters per second

3
Using Scientific Notation

• B. Scientific Notation
• 1. A way of expressing a value as the value of
  a number between 1 and 10 and a power of 10.

4
Using Scientific Notation

• B. Scientific Notation
• 2. Is a shortcut to writing all of the digits
  in a number.
• a. 300,000,000 3.0 x 10 8
• the exponent 8 tells you that the decimal
  point is
• really 8 places to the right of the 3.
• b. 0.00086 8.6 x 10 -4
• 1) The negative exponent means the number
  is a
• decimal (small).
• 2) The exponent of a 4 tells you how many
  
• decimal places there are to the left
  of the
• 8.6.

5
Using Scientific Notation

• B. Scientific Notation
• 3. Makes very large or very small numbers easier
  to work with.

6
Using Scientific Notation

• C. Multiplying in Scientific Notation
• 1. Multiply the numbers that appear before
  the
• multiplication sign.
• 2. Add the exponents.
• 3. Make sure answer is in notation form.
• D. Example of multiplying
• 1. How far does light travel in 500 seconds?
• (Speed of light)(time) distance (on
  board)

7
Using Scientific Notation

• D. Example of multiplying
• 1. How far does light travel in 500
• seconds?
• (Speed of light)(time) distance
• 300,000,000m/s X 500s ?
• (3.0 x 108 m/s) X (5.0 x 102 s)
• 15 x 1010 m
• 1.5 x 1011 m

8
Using Scientific Notation

• Remember number before the power of ten must
  be greater than1 and less than 10.
• If you need to move the decimal to the Left
  ADD an exponent, or to the
• Right SUBTRACT an exponent
• (LARS)

9
Using Scientific Notation

• E. When Dividing in Scientific Notation
• 1. Divide the numbers that appear before the
  exponents
• 2. Subtract the exponents.
• F. Example of Dividing
• How long will it take for light from the sun
  to reach the
• Earth? (on board)
• Distance velocity time
• Answer 1.5 x 1011m 3.0 x 108m/s .5 x 103s
  5.0 x 102s

10
SI Units of Measurement

• A. For a measurement to make sense, it requires
  both a number and a unit.
• 1. Always use measurements in numbers
  and units so that their meaning is clear.
• 2. Scientists use a set of measuring
  units called SI, or the International System
  of Units.
• 3. By using one system of units,
  scientists can readily reproduce one anothers
  measurements.

11
SI Units of Measurement

• B. Base units and derived units
• 1. Base Units- the 7 metric units on which
  the
• metric system is based.
• 2. Derived Units- are the additional units
  that
• come from combinations of the base units.
• 3. Derived units include volume (length x
• width x height) and density
  (mass/volume).

12
SI Units of Measurement

• C. Metric Prefixes
• 1. Indicates how many times a unit should
  be multiplied or
• divided by ten.
• 2. 9ms 9/1000 s 0.009 seconds
• 3. 12 km 12 x 1000 m 12,000 m
• 4. Are used in non-metric units as well
• a. gigabytes 1,000,000,000 bytes
• b. megapixels 1,000,000 pixels
• 5. conversion factor a ratio of equivalent
  measurements that
• is used to convert a quantity expressed
  in one unit to another
• unit.
• convert from 8848 m to km (on board)
• notice that the meter units cancel