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)

• Uses prefixes to identify larger or smaller units of measure

Common Prefixes

Symbol Multiple

kilo K 1000

centi c .01

milli m .001

Metric Conversions - Length

Km m dm cmmm

x 1000 x 10 x 10 x 10

÷ 1000 ÷ 10 ÷ 10 ÷10

Metric Conversions - Volume

Kl l dl clml

x 1000 x 10 x 10 x 10

÷ 1000 ÷ 10 ÷ 10 ÷10

Metric Conversions - Mass

Kg g dg cgmg

x 1000 x 10 x 10 x 10

÷ 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 cm2

(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. cm3) and can be calculated using specific formulas

Calculating the volume of a rectangular prismVolume of a rectangular prism = length x width x height (l x w x h)

Length = 10 cmWidth = 3 cmHeight = 4 cm

Volume = l x w x h = 10 cm x 3 cm x 4 cm = 120 cm3

10 cm

4 c

m

3 cm

Calculating the volumeof 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 cm3

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

WeightWeight 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/s² (Earth’s surface gravity)

For a person with a mass of 45 Kg

Weight = 45 Kg X 9.8 m/s²

= 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•Density is the mass of a specific volume of an object

•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/cm3 )

•Since the density of water is 1 g/cm3 anything with a density less than 1 g/cm3 will float in water and anything greater will sink

Calculating Density

Density = Mass

Volume Density of Object A = 150 grams = 5 g/cm³

30 cm³

A

5 cm

2 cm

3 cm

Volume of Object A = 5 cm x 2 cm x 3 cm = 30 cm³

Mass of Object A = 150 grams(measured on a balance)