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.

• Independent variable: added water• Dependent variable: green grass• Control group: grass not watered• Experimental group: grass watered

Example: This bottle of milk stinks.

• Independent variable: closed or open bottle• Dependent variable: stinky milk• Control group: closed bottle of milk• Experimental group: open bottle of milk

Measurement

• Agreed upon• International (“Systeme International”; “SI”)• Unchanging• Available

S.I.

• 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.