Physical Quantities (OCR A Level Physics)

• 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 is used to represent the physical quantity of velocity (or speed)
  • The letter V can be used to represent volume, potential or voltage

• The units provide the context as to what v or 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