Transcript Measurements and the Metric System
Measurements and the Metric System
The Metric System
• A universal measurement system • Also called the International System or SI units • Only three countries worldwide don’t use the metric system (USA, Burma, and Liberia)
The Metric System
• Based on multiples of ten (this makes it easy to use)
Common Prefixes Symbol Multiple
kilo K 1000 • Uses prefixes to identify larger or smaller units of measure centi c .01
milli m .001
Metric Conversions - Length
x 1000 x 10 x 10 x 10
Km m dm cm mm
÷ 1000 ÷ 10 ÷ 10 ÷10
Kl
Metric Conversions - Volume
x 1000 x 10 x 10 x 10
l dl cl ml
÷ 1000 ÷ 10 ÷ 10 ÷10
Kg
Metric Conversions - Mass
x 1000 x 10 x 10 x 10
g dg cg mg
÷ 1000 ÷ 10 ÷ 10 ÷10
Length
• • •
A measure of linear distance Basic unit of length is the meter (m) Measurements made with a meter stick or metric ruler
•The entire meter stick represents one meter •Each number represents a centimeter (there are 100 centimeters in a meter) •Each little line is a millimeter (there are 1000 millimeters in a meter)
Area
•
The amount of surface included within a set of boundaries
•
Determined by measuring the length and width of an object, then multiplying
Length = 14 cm Width = 7 cm Area = 14 cm x 7 cm = 98 cm
2 (Area is always expressed in square units)
Volume
•
Volume is the space that an object occupies
•
Represents the length, width, and height of an object
•
For solids, measurements are based on units of length (ex. cm 3 ) and can be calculated using specific formulas
Calculating the volume of a rectangular prism
Volume of a rectangular prism = length x width x height (l x w x h) 10 cm
Length = 10 cm Width = 3 cm Height = 4 cm
3 cm
Volume = l x w x h = 10 cm x 3 cm x 4 cm = 120 cm
3
Calculating the volume of a cylinder
Diameter = 10 cm 20 cm
Volume of a liquid
•A graduated cylinder is used to accurately measure the volume of liquids in milliliters •Determine the volume in a graduated cylinder by reading the bottom of the meniscus at eye level •Once the volume of a liquid is known, it can be converted to a “solid volume” by using the formula 1 ml = 1 cm
3
Mass
•
Mass is a measure of the amount of matter in an object
•
Mass is measured in grams using a balance
•
The mass of an object remains the same, no matter where in the universe it is measured
Weight
Weight is a measure of the gravitational force exerted on an object by a massive body
•
Weight is measured in Newtons (N) using a spring scale
•
Weight varies from place to place depending on the strength of the gravitational force Your weight on Earth = Mass (Kg) X 9.8 m/s ² (Earth’s surface gravity) For a person with a mass of 45 Kg Weight = 45 Kg X 9.8 m/s ² = 441 N
Gravity
Gravity is the force of attraction between objects The strength of the gravitational force between objects depends on: - The distance between the objects ( the gravitational force between objects decreases with distance) -Mass ( the greater the mass of an object, the greater it’s gravitational force)
Density
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Density is the mass of a specific volume of an object
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Density is calculated by dividing the mass of an object by its volume
•
Units for density are usually expressed in grams per cubic centimeter (g/cm 3 )
•Since the density of water is 1
g/cm 3
anything with a density less than 1 g/cm
3 will
float in water and anything greater will sink
Calculating Density
A 3 cm Volume of Object A = 5 cm x 2 cm x 3 cm = 30 cm ³ Mass of Object A = 150 grams (measured on a balance) 2 cm 5 cm
Density = Mass Volume
Density of Object A = 150 grams = 5 g/cm ³ 30 cm ³