CIE AS Physics

Revision Notes

Syllabus Edition

First teaching 2020

Last exams 2024

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1.1.1 Physical Quantities

Test Yourself

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 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

What is a Physical Quantity, downloadable AS & A Level Physics revision notes

All physical quantities must have a numerical magnitude and a unit

 

Estimating Physical Quantities

  • 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

1-1-1-estimating-physical-quantities--table-_21-1-1-estimating-physical-quantities--table-_2

Worked example

Estimate the energy required for an adult man to walk up a flight of stairs.

Estimating Physical Quantities, downloadable AS & A Level Physics revision notes

Exam Tip

The mark scheme for calculations involving estimates are normally quite generous and offer a range of values as the final answer. Some common estimates are:

  • Mass of an adult = 70 kg
  • Gravitational field strength, g = 10 m s-2
  • Mass of a car = 1500 kg
  • Wavelength of visible light = 400 nm (violet) – 700 nm (red)

Many values are already given in your data booklet that therefore may not be given in the question, so make sure to check there too! 

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