Quantities and Units

The essentials you need to know to understand the rest of Physics. This is where you start!

Quantities vs. Units

Let's start A Level Physics with a look at the quantities we measure and the units they are measured in.

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Base Units

There are just 7 base units from which we can make all the others. These are all precisely defined so that 1 kg is always 1 kg.

To find out more I recommend the following videos:

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Derived Units

Newtons, joules and even the volt can all be made up from combinations of the 7 base units. This video shows how.

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Unit Prefixes

Because Physics is about absolutely everything in the Universe we have to cover both the extremely large and also the incredibly small. Rather than writing numbers like 100000000 or 0.0000000000001 we can use prefixes from the Gigalarge to the femtosmall.

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Estimating Physical Quantities

As you develop your Physics you will be able to recall and recognise the size of common objects - although you don't have to remember the exact number you do need to be close enough to the correct order of magnitude.

The Greek Alphabet

As you work through A Level Physics there will be a whole new set of symbols you need to know that represent units and quantities. These are the letters you need to know from the Greek Alphabet.

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