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# Measurement&Conversions

## on Dec 01, 2008

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## Measurement&ConversionsPresentation Transcript

• We need a reliable system of measurement to obtain useful data.
• Before standardized units:
• Measurement used to be subjective
• One “foot” really was the length of a human foot. Obviously, foot size varies.
• In order to have consistency, there is a need for a standardized system of units.
• One foot should be the same length for every person.
• International System (S.I.) of Units:
• Developed in the late 1700s
• You may recognize as the “Metric” system.
• Our “English” system was eventually standardized also, but the S.I. system is used by most countries and the international scientific community.
• We will use the S.I. system in class.
• Based on 10– What is English system based on?
• S.I. Base Units:
• Base units can be measured directly. Units for other measurements are calculated from base units.
• * One meter is equal to approximately 3 feet, 3 inches.
s second time K, °C Kelvin, deg. Celsius temperature g gram mass m meter length S.I. Abbrev. S.I. Unit Measurement
• Prefixes
• kilo- (k), 1000 times
• centi- (c), 1/100 th (There are 100 cents in one dollar.)
• milli- (m), 1/1000 th
• Example:
• 1 km = 1000 meters
• 1 cm = 0.01 meter (100 cm = 1 m)
• 1 mm = 0.001 meter (1000 mm = 1 m)
• What does this mean?
• 1 kilometer (km) is approximately 0.6 miles
• 1 meter (m) is approximately the length from your fingertips to your opposite shoulder
• 1 centimeter (cm) is approximately the width of the tip of your pinky
• 2.54 cm = 1 inch
• 1 millimeter (mm) is approximately the width of a paperclip wire
• Is this a ridiculous speed limit sign?
• What does it mean?
• 120 km/h = 75 mi/h
• How do they fit together?
• 10 mm = 1 cm
• 100 cm = 1 m
• 1000 m = 1 km
• Converting units:
• Convert 1 km to centimeters.
• Known: 1 km = 1000 m, 1 m = 100 cm
• Therefore, 1000 m = 1 and 100 cm = 1
• 1 km 1 m
• 1 km x 1000 m x 100 cm = 100,000 cm
• 1 km 1 m
• 1 km 1000 m 100 cm = 100,000 cm
• 1 km 1 m
• Mass is a measure of the amount of matter (stuff) that something is made of.
Would you expect an elephant or a mouse to have a greater mass? An elephant is made of a greater amount of stuff and, therefore, has a greater mass. In this class we will measure mass in grams or kilograms . The mass of a penny is about 2 ½ to 3 grams. The mass of your teacher is about 50,000 grams (50 kg). The mass of an elephant is about 5,000,000 grams (5,000 kg).
• Are mass and weight the same? We will compare mass and weight later. However, we measure mass with the same equipment we use to measure weight– a scale or “beam balance”. VB-302-3000 Electronic Precision Balance Scale [Online]. Flex Weigh Direct 2006-07. http://www.flexweighdirect.com/vb3023000/ The mass of this object is 2000 grams.
• S.I. Derived Units
• Derived units are combinations of base units.
• Measurements of size:
• Length is a 1-dimensional
• size measured in
• meters (m)  base unit.
• Area is a 2-dimensional size
• measured in
• square meters (m 2 ).
• Volume is a 3-dimensional
• size measured in
• cubic meters (m 3 ).
• Area and volume are
• given in derived units.
3 m 3 m 3 m 3 m 3 m 3 m The length of this line = 3 m. The area of this square = 3 m x 3 m = 9 m 2 . The volume of this cube = 3 m x 3 m x 3m = 27 m 3 .
• What is the area of a sheet of computer paper?
•  Area is a 2-dimensional measurement.
•  Area = length x width
•  Area = 0.22 m x 0.28 m
•  Area = 0.062 m 2
• Square meters are a
• combination of meters
• (meters x meters) 
• derived unit.
0.22 m 0.28 m
• Volume is a measure of the amount of space something occupies or contains.
• Imagine a pool ball and a tennis ball.
• Compare the mass and volume of the two objects.
• The two objects occupy approximately the same amount of space and so have approximately equal volumes.
• The pool ball has a much greater mass than the tennis ball, as you can tell when you pick up the two objects.
• Compare the mass and volume of a basketball and a bowling ball.
• We use volume measurements everyday. Example: The gas tank in my car contains 15 gallons of gasoline (when it is full). Example: A bread recipe calls for 2 cups of water and 3 tablespoons of oil. In science class, the unit we will use to measure the volumes of liquids is the liter (L) . Think of the amount of space occupied by a 1-liter or 2-liter bottle of soda.
• The equipment we will use to measure liquid volume in class will be the beaker and the graduated cylinder . Beakers are generally used to measure larger volumes. They do not have many markings. 250 ml Bomex Glass Beaker [Online]. Research Laboratory Supply, Inc. 2008. Researchsupply.net Graduated Cylinder, Glass, 50 ml [Online]. Science Stuff, Inc. 2008. Sciencestuff.com. Graduated cylinders get their name from many small markings (similar to a ruler) that are used to take a wide variety of large and small measurements.
• What volume of water does an Olympic-sized swimming pool contain?
•  Volume is a 3-dimensional measurement.
•  Volume = length x width x height (depth).
•  Since area = length x width,
• then volume = area x height.
width = 25 m length = 50 m depth = 2 m Volume = l x w x d Volume = 50 m x 25 m x 2 m Volume = 2500 m 3
• 25 m 2 m 50 m Volume = 2 m x 25 m x 50 m Volume = 2500 m 3 This volume is equivalent to 2500 cubes of 1 m 3 (1 m x 1 m x 1 m)
• So is volume measured in cubic meters (m 3 ) or in liters (L)?
• Solids measured in m 3 only.
• Liquids and gases measured in m 3 or L.
• What is the connection?
• 1 cm 3 = 1 mL for liquids and gases
•  This is the conversion factor , which allows us to convert a measurement from one type of units to another.