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PHYSICAL SCIENCE
A
NOTES
SI FUNDAMENTAL UNITS
The whole System
International is based on 7 fundamental
(base) units:
|
Unit
|
Symbol
|
Measures?
|
|
meter
|
m
|
distance, length
|
|
second
|
s
|
time
|
|
kilogram*
|
kg
|
mass
|
|
kelvin
|
K
|
temperature
(based on absolute zero)
|
|
ampere
|
A
|
electric current
|
|
mole
|
mol
|
amount of substance
(related to number of atoms)
|
|
candela
|
cd
|
brightness/intensity of light
|
*Note
that kilogram is the FUNDAMENTAL unit for mass; -gram is the ROOT word for
mass
in SI
A
measurement is only valid
if it has
a number AND a unit.
- In math, the number
is
often enough,
but in science it is not.
- 7 as an answer
doesn't
say anything.
7 seconds? 7 meters? 7 centimeters?
SI PREFIXES
Prefixes
in SI allow you to make a
unit bigger or smaller.
- They come before
the
unit, like kilometer
(1 000 m - big!) or millisecond
(0.001 s - small!).
|
Prefix
|
Symbol
|
Stands for...
|
|
mega-
|
M
|
million
|
1 000 000 |
|
kilo-
|
k
|
thousand
|
1 000 |
|
hecto-
|
h
|
hundred
|
100 |
|
deka-
|
da (or dk)
|
ten
|
10 |
|
(no prefix)
|
1
|
one
|
1 |
|
deci-
|
d
|
tenth
|
0.1 (1/10) |
|
centi-
|
c
|
hundreth
|
0.01 (1/100) |
|
milli-
|
m
|
thousandth
|
0.001 (1/1000) |
|
micro- |
μ |
millionth |
0.00001 (1/1000000) |
|