What is a Physical Quantity?
- 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
Examiner Tip
The same letter in the Greek or English alphabet can often refer to a different quantity depending on its context in Physics. Make sure you understand what each variable in every equation is before you use it, in order to avoid confusion.
