UNITS

"It is much easier to make measurements than to know exactly what you are measuring"
J.W.N. Sullivan

•  Physics is an experimental science.

• Measurements have a "size (number)" and "unit name", e.g. 6 metres, 4 kilograms.

All physical quantities can be measured in terms of the units of length, time, mass, temperature, electric current, amount of substance and luminous intensity.
e.g. speed = length/time.
This course will use only the first 4 units.

• A system of units is a particular set of units used to measure these quantities.

In this course we will use almost exclusively the SI (System Internationale) system.  However, since in some mechanics and thermodynamics situations, the USA continues to use the British   system, I will occasionally mention these units.

Quantity	SI	British
Length	metre	foot
Mass	kilogram	slug
Time	second	second
Temperature	kelvin	fahrenheit
Electric current	ampere
Amount of substance	mole
Luminous intensity	candela

“Of course, America had often been discovered before Columbus, but it had always been hushed up”

Oscar Wilde

Dr. C. L. Davis

Physics Department

University of Louisville

email: c.l.davis@louisville.edu