MEASUREMENTThe Metric System and Conversions

Number vs. Quantity• Quantity - number + unit

UNITS MATTER!!

The Metric System

• Easier to use because it is based on powers of 10.• A metric unit has two parts:

A prefix and a base unit• Example cm, mL, mg• The prefix tells you how many times to divide or multiply

by 10• KHD DCM• King (kilo=1000) Drinking (deci=1/10)• Henry (Hecta =100) Chocolate (centi=1/100)• Died ( Deka =10) Milk (Milli=1/1000)

Some Base Units

• Length - meter(m) - more than a yard

• Mass - grams(g) - about a raisin

• Volume - Liter(L) - half of a two liter bottle

Some Prefixes• kilo• 1 km = 1000 m• Hecto• 1 hm = 100 m• Deka• 1 dkm = 10 m• deci• 1 dm = .1 m• centi • 1 cm = .01 m• milli• 1 mm = .001 m• Micro• 1 µm = .000001 m • Nano• 1 nm = .000000001 m

Dimensional Analysis

• The “Factor-Label” Method

– Units, or “labels” are canceled, or “factored” out

Dimensional Analysis

• Steps:

1. Identify starting & ending units.

2. Line up conversion factors so units cancel.

3. Multiply all top numbers & divide by each bottom number.

4. Check units & answer.

Conversion Factors

• Conversion factor- a fraction based on a definition and equal to 1– Example:

• 1 cm = 0.01 m

• Conversion factors possible: 1 cm 0.01 m0.01 m OR 1 cm

Example 1

• Convert 77 kg to grams

Example 2

• Convert .0087 mL to L

Example 3

• Convert 12 yds to ft

Example 4

• Convert 32.4 cm to yards

Example 5

• Convert 50 mm to km

Example 6

• Convert 4.5 x 10-5 yr to min

Multi Dimension Conversions

• Remember……..• 1 dimension at a time!

Example 1

• Convert 17.2 mi/hr to m/s

Example 2

• Convert 44 cm3 to in3

Example 3

• Convert 4.5 lb/ft3 to g/cm3

Questions?

• “The ultimate measure of a person is not where they stand in moments of comfort and convenience, but where the stand in times of challenge and controversy.”