Physics is an experimental
science
Experimental Design
• Independent variable = the parameter being
changed. Examples: time, temperature, pH,
salt. Independent variable is expressed on the
X axis (horizontal axis).
• Dependent variable = the effect or the result
being examined. Examples: distance, velocity,
amount of product formed. Dependent
variable is expressed on the Y axis (vertical
axis).
Experimental Design
• Control group = original or “same, old”
condition
• Experimental or test group = group being
subjected to new conditions
Example: The grass is brown.
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Independent variable: added water
Dependent variable: green grass
Control group: grass not watered
Experimental group: grass watered
Example: This bottle of milk stinks.
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Independent variable: closed or open bottle
Dependent variable: stinky milk
Control group: closed bottle of milk
Experimental group: open bottle of milk
Measurement
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Agreed upon
International (“Systeme International”; “SI”)
Unchanging
Available
S.I.
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Length: meter
Time: second
Mass: kilogram
Temperature: kelvin (kelvin = degrees
Centrigrade plus 273)
Prefixes for powers of 10
• See page 1 of the Reference Table
Scientific Notation
• M x 10^n
• M is the mantissa
• M is between 1 and 10
• n is the exponent
angles
• Angles are measured in degrees
• Use protractor
• Use trigonometry
• Accuracy refers to how well a measurement
agrees with an accepted value. Perform error
analysis to study accuracy.
• (measured – accepted)/(accepted) x 100%
• Precision describes how well a measuring device
can produce a measurement. The limit of
precision is ½ of the smallest division of that
device. Precision tells you how “tight” a set of
measurements are among themselves.
• Reliable means BOTH accurate and precise.