Derived units

Derived units are math constructions using base unit. There are many important derived units. Examples of derived unit are speed, gas mileage, wages ( dollars per hour) and more. A government site describing derived units can be useful. http://physics.nist.gov/cuu/Units/units.html

The units for measuring speed are miles/ hour and meters/ second. These are constructed using the length and time units. These types of units come naturally from measurements. When you read your car speedometer you see 60 miles/ hour or 100 kilometers/ hour. We use derived units every day.

Advantages of the metric units

The most important advantage of themetric and SI units is that switches from one unit to another is done bymoving the decimal point. ALL the units for a specific quality like length are related by some multiple of ten.

For example 2 meters is equal to 200 centimeters. The conversion from meters to centimeters is done by mulitplying by (100 cm / 1 meter)

2 meters x ( 100 centimeters / 1 meter ) = 200 centimeters

The meter units cancel out. The decimal point moves 2 places to the right.

Conversion factors are also explained at these siteshttp://scphillips.com/units/

Metric and SI unit prefixes

The conversion from one unit to another is done using multiples of ten. A site with more prefixes is NIST http://physics.nist.gov/cuu/Units/

Name

Trillion

Billion

Million

Thousand

Hundred

Ten

Tenth

Hundredth

Thousandth

Millionth

Billionth

Trillionth

.

tera-

giga-

mega-

kilo-

hecto-

deca-

deci-

centi-

milli-

micro-

nano-

pico-

T

G

M

k

h

da

d

c

m

m

n

p

1,000,000,000,000

1,000,000,000

1,000,000

1,000

100

10

1/10

1/100

1/1000

1 / 1,000,000

1 / 1,000,000,000

1 / 1,000,000,000,000