Physics Experimental Techniques and Measurement Vocabulary

Vocabulary terms and definitions related to physical quantities, units, experimental errors, and measurement accuracy.

Accuracy

• a measure of how close a measured value is to the true, accepted value

• if an experiment result is accurate it is very close to the true value

• in practice, the true value is usually not known

SI units

Mass - kilograms (kg)

Amount of substance - moles (mol)

Temperature - Kelvin (K)

Distance - meters (m)

Electric current - Amperes (A)

Time - seconds (s)

Luminous intensity - Candela (cd)

SI units of energy

Kinetic energy = ½ x mass x velocity²

Units = kgm²s^-2

SI units of force

Force = mass x acceleration

Units = kgms^-2

Validity

The property of a measurement if it measures what it is supposed to be measuring. An experimental procedure is valid if the obtained values provide an answer to the question being asked.

Random Error

An error that occurs due to unexpected, unpredictable changes during an experiment, which can cause repeated results to differ from one another.

Anomaly

A data point or value in a set of results that does not fit the trend of the data and is therefore an unexpected result (also known as an outlier). These can happen as a result of random errors during an experiment.

Systematic Error

An error that occurs due to faults in equipment or experimental method, causing results to differ by the same amount each time, making them predictable. They can occur due to not calibrating an instrument correctly.

Three ways of reducing random error

• Take at least three repeats and calculate a mean (increases likelihood of identifying anomalies)

• Use computers/data loggers

• Use higher resolution equipment

How can systematic error be reduced?

Calibrate apparatus before using.

Precision

A measure of how consistent /close together repeat readings are.

Repeatable Experiment

An experiment where the original experimenter can redo the procedure with the same equipment and method and obtain the same results.

Reproducible Experiment

An experiment that can be redone by a different person or with different techniques and equipment while finding the same results.

Resolution

The smallest change in the quantity being measured that gives a recognisable change in reading.

Absolute uncertainty

Uncertainty given as a fixed quantity.

Reducing fractional uncertainty

Measure larger quantities

Reading

A value found when one single point on an instrument is observed.

Measurement

A value found by taking the difference between two readings.

Order of Magnitude

Powers of ten which describe the size of an object and are used to compare the relative sizes of objects.