 To add a prefix to a unit, divide the number with the value of prefix you
want to add with the unit.
PHYSICS
Units & Measurements
SI – System international
OR International system of Units.
3.4 m =
1. Seven Basic Units in SI System.
 If you are multiplying, add the indices, so
y 6 × y 2 = y 6 + 2 = y8
 If you are dividing, subtract the indices, so
y 6 ÷ y 2 = y 6 – 2 = y4
However, these only apply to powers of the same number.
Prefix – Symbol – Factor
*deci – d – 10 – 1
hecto – h – 102
*centi – c – 10 – 2
– k – 103
*milli – m – 10 – 3
*mega – M – 106
*micro – µ – 10 – 6
*giga – G – 109
*nano – n – 10 – 9
– p – 10 – 12
*tera
– T – 1012
pico
peta
– P – 1015
femto – f – 10 – 15
exa
– E – 10
atto
nm = 8.3 nm.
 If you are doing a power of a power, multiply the indices,
so (y 6) 2 = y 6×2 = y 12
deka – da – 101
18
cm = 340 cm.
3. The Three Laws of Powers / Indices:
2. Prefixes that can be attached to the Units.
*kilo
km = 45 km.
0.00000000
* kilogram, “kg” for mass,
* metre, “m” for length
* second, “s” for time
* Kelvin, “K” for temperature
* Ampere, “A” for Electric Current
Candela, “cd” for luminous intensity
mole, “mol” for amount of substance.
Prefix – Symbol – Factor
 eg. 45000 m =
– a – 10
 For example, 10 5 × 10 4 = 10 9, but you cannot simplify 10 5 × 2 4.
Some additional Information about powers
 Anything to the power 0 is 1.
so
6 0 = 1,
y0=1
and 27549.26 0 = 1
 Anything to the power 1 is the number itself.
so
6 1 = 6,
x1=x
and 0.3 1 = 0.3 .
 In a power with fractions, the bottom of the fraction means a root, and
the top of it means a power.
so
 Negative powers mean “1 over”.
– 18
To remove a prefix added to the unit, multiply the number with the
value of prefix.
eg.
3.7 MHz = 3.7 × 106 𝐻𝑧
47 µF
= 47 × 10−6 𝐹
35 ns
= 35 × 10−9 𝑠
340 cm
=
so
 You can expand brackets involving things multiplied or divided in the
obvious way.
so
 You cannot expand brackets involving things added or subtracted.
So, you cannot simplify √(𝑦 2 + 1), or (a + b)10.