Metric prefixes

Also called SI prefixes

Metric prefixes are the multipliers attached to SI units, such as kilo for a thousand and milli for a thousandth. The AP tables print the set from pico to tera, and each one must be converted away before substitution.

The prefixes table appears on every AP Physics table of information:

PrefixSymbolFactor
teraT101210^{12}
gigaG10910^{9}
megaM10610^{6}
kilok10310^{3}
centic10−210^{-2}
millim10−310^{-3}
microμ10−610^{-6}
nanon10−910^{-9}
picop10−1210^{-12}

Note what is not there: deci, deca and hecto are absent, and centi is the only one between 10−310^{-3} and 10310^{3}.

Case matters. A capital M is mega and a lowercase m is milli, a factor of 10910^9 apart, and the same lowercase m is also the symbol for the metre.

The trap that actually costs marks is squared and cubed units, because the prefix gets raised too. Since 1 cm=10−2 m1\ \text{cm} = 10^{-2}\ \text{m}, it follows that 1 cm2=10−4 m21\ \text{cm}^2 = 10^{-4}\ \text{m}^2 and 1 cm3=10−6 m31\ \text{cm}^3 = 10^{-6}\ \text{m}^3. That is why a density of 1 g/cm31\ \text{g/cm}^3 becomes 1000 kg/m31000\ \text{kg/m}^3, and not the 0.1 kg/m30.1\ \text{kg/m}^3 you get by forgetting to cube the prefix. A pipe cross section quoted in cm2\text{cm}^2 needs the same treatment before it goes into A1v1=A2v2A_1 v_1 = A_2 v_2.

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