Sunny's Astro Notes: CONVERTING UNITS

How to Switch from One Measurement Unit to Another

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When we convert units, we're really just changing the way we describe the same quantity.

For instance:

1 Foot = 12 Inches

'One foot' and 'twelve inches' are simply two different ways to describe the same distance.

In a way, converting units is just a fancy way of multiplying by one:

(1 Foot / 12 Inches) = 1 = (12 Inches / 1 Foot)

So, you can multiply by this 'fancy one' anytime you choose:

3.5ft * (12in/1ft) = 3.5*12in = 42in

The name for what is in the parentheses is the 'conversion factor'.

Notice that the units we started with (feet) had to be in the denominator of the conversion factor so that those units could cancel out.

If the units we're converting from are raised to a power, we have to account for this:

3ft*3ft = 9ft^2 = 1yd^2

So, we can take any conversion factor and raise it to a power to cancel units to that power:


Some Related Notes:
Lorentz Transformations -- Measurements with a Moving Reference Frame

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  Sunny Snaith --
Snail Mail: Post Office Box 503, Decatur, GA 30031-0503
Last revision: June 28, 1999

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