The History of MeasurementThe History of Measurement

MeasurementMeasurement

• One of the steps of the scientific methods involves making observations.

• An observation is information gathered by our five senses.

Types of ObservationsTypes of Observations

• There are two types of observations:

• Qualitative Observations

• Quantitative Observations

Qualitative Observations involve describing the properties of an object using words.

Examples of Qualitative Observations

Examples of Qualitative Observations

• The fire engine is red.

• The fire engine is big.

• The fire engine is shiny.

• The fire engine has silver doors on the side.

Your Qualitative ObservationsYour Qualitative Observations

• Make and record five Qualitative Observations about yourself.

Quantitative ObservationsQuantitative Observations

• Quantitative Observations involve measurements.

• A measurement includes a number and a unit.

• The following physical properties can be measured:– Length– Width– Height– Mass– Temperature– Viscosity– Density– Etc.

History of MeasurementHistory of Measurement

• Objects were measured to aid commerce.

• Many early measurements were based on body parts.

The CubitThe Cubit

• A cubit is the distance from your elbow to the tip of your middle finger.

SpanSpan

• A span is the distance between the thumb and the little finger while the hand is outstretched.

PalmPalm

• A palm is the width of the closed hand.

DigitDigit

• A digit is the distance across the index finger.

Body Part Measurement PracticeBody Part Measurement Practice

• Measure the following using the unit indicated:

1.Length of the room in:1. Cubits

2. Spans

2.Length of the textbook in:1. Digits

2. Palms

3. Spans

4. Cubits

Problems with Body Part Measurments

Problems with Body Part Measurments

1. Body part measurements are not accurate when dealing with fractions of body parts.

2. People have different sized body parts.

3. The ratio of cubit to span may be different for different people.

Standard Systems of MeasurementStandard Systems of Measurement

• Standard Systems are based on some standard to measure against.

• Early standard systems often used body parts of the king or ruler as the standard distance.

• When the king died, a new measurement system would be created.

Imperial System of MeasurementImperial System of Measurement

• 1 foot = average length of a man’s foot

• 1 yard = average length of a legionaire’s stride

• 1 inch = width of a thumb

Imperial System ConversionsImperial System Conversions

• 12 inches = 1 foot

• 3 feet = 1 yard

• 1760 yards = 1 mile

• 1 league = 3 miles

• 6 feet = 1 fathom

• 22 yards = 1 chain

How many inches in 2.5 leagues?How many inches in 2.5 leagues?

• 2.5 x 3 x 1760 x 3 x 12 =

The Metric SystemThe Metric System

• In 1799, Napoleon commissioned a survey to find the length from the equator to the North Pole.

• One ten-millionth of this distance was defined as a metre.

• Conversions from one unit to another were all done by factors of 10.

SI Units of Measurement: Base Units

SI Units of Measurement: Base Units

Name Symbol Unit of

metre m length

kilogram kg mass

second s time

ampere A electric current

kelvin Kthermodynamic temperature

mole molamount of substance

candela cd luminous intensity

Your Quantitative ObservationsYour Quantitative Observations

• Make and record 5 metric quantitative observations about yourself.

Scalars and VectorsScalars and Vectors

• Scalar Quantities include a numeral and a unit only.

• Examples are: 75 kg, 25 seconds

• Vector Quantities includes a numeral, a unit and a direction.

• Examples are 125 km [N], 2.4 m/s [NW],

• 9.8 m/s/s [down]

Vectors Scalars

Displacement Distance

Velocity Speed

Acceleration Acceleration

Time

Mass

Energy

Force

Electric Field

Voltage

• Position is a vector quantity that measures the distance an object is from a reference point and the direction that the object is from the reference point.

• Displacement is the vector quantity that records the change in position of an object.