• Speed and velocity are examples of physical quantities; both can be measured
• All physical quantities consist of a numerical magnitude and a unit
• In physics, every letter of the alphabet (and most of the Greek alphabet) is used to represent these physical quantities
• These letters, without any context, are meaningless
• To represent a physical quantity, it must contain both a numerical value and the?unit?in which it was measured
• The letter?v?be used to represent the physical quantities of velocity, volume or voltage
• The units provide the context as to what?v?refers to
  • If?v?represents velocity, the unit would be?m s^–1
  • If?v?represents volume, the unit would be?m³
  • If?v?represents voltage, the unit would be?V

All physical quantities must have a numerical magnitude and a unit

• There are important physical quantities to learn in physics
• It is useful to know these physical quantities, they are particularly useful when making estimates
• A few examples of useful quantities to memorise are given in the table below (this is by no means an exhaustive list)

Estimating Physical Quantities Table