Metric SystemMetric System

Length(L)

Length(L)

Mass(M)

Mass(M)

Volume(V)

Volume(V)

Time(t)

Time(t)

Temperature(T)

Temperature(T)

The Metric System---The Universal Language of Measurement---

• Metric System – scientists & engineers use this language to communicate• The metric system is often referred to as the

International System (“SI”) of Units• The metric system is based on the number

10 and multiples of 10.

Metric Quantities

• We will encounter a number of (base) metric quantities through the course of this class.

• For now we will just focus on two:• Length• Mass

LengthThe distance between two points

• Meter (m) – the basic unit of length in the metric system

If it is not appropriate to measure something in meters we can use metric prefixes to describe quantities that are larger or smaller than a meter.

• Example if something is smaller we can use the centimeter• Centimeter (cm) – one hundredth of a meter

1 cm = 1/100 m = 0.01 m100 cm = 1 m

• Example: if something is bigger we can use the kilometer:Kilometer – one thousand meters

1 km = 1000m1 m = 1/1000 km

Massa measure of the amount of matter in an object

• Kilogram (kg) – the basic unit of mass in the SI system

• Example if something is smaller we can use the gram (which is at the base of the scale, but is not the “base unit” of mass).

• Gram (g) – one thousandth of a kilogram1 g = 1/1000 kg = 0.001 kg1000 g = 1 kg

• Example: if something is smaller still, then we can use a different prefix.

• Milligram (mg)– one thousandth of a gram1 mg = 1/1000 g = 0.001 g1000 mg = 1 g

Metric Prefixes• The metric prefixes all have a mathematical meaning. If

you know the meaning of each prefix then it is VERY easy to convert from one unit to the other.

• Many of you have memorized some mnemonic for the metric prefixes (“King Henry…”)

– FORGET THIS …IT IS CRAP!- Memorizing this does NOT mean that you know it, understand it, and

can work with it. - Actually, students who use this are often the ones that make the most

mistakes.

Prefix Symbol Meaningmega M 1000000 = 106 million

kilo- k 1000 thousand

hecto- h 200 hundred

deka- da 10 ten

-Base Unit- ----- 1

deci- d 0.1 tenth

centi- c 0.01 hundredth

milli- m 0.001 thousandth

micro μ 0.000001 = 10-6 millionth

nano n 0.000000001 = 10-9 billionth

Metric Prefixes

Metric Prefixes(same info in a different manner)

nano

(n)

=

10-9

micro

(μ)

=

10-6

milli(m)

=

.001

=

1/1000

centi(c)

=

.01

=

1/100

deci(d)

=

.1

=

1/10

Base

Unit

=

1

deka(da)

=

10

hecto(h)

=

100

kilo(k)

=

1000

Mega(M)

=

106

Example:

Convert 25cm to meters using dimensional analysis.

Solution

mcm

mcm

mcm

mcm

mcm

25.100

1)25(

____

__)25(

??25

Convert 25cm to meters using dimensional analysis.

Set up a conversion fraction so that the units that you have will cancel out.

Put the appropriate values in the fraction and do the math.

You’ll get the right answer every time without worrying, “oh, do I move the decimal to the right or to the left.” JUST DO THE MATH!!!!!

Know the METRIC SYSTEM and use DIMENSIONAL ANALYSIS…it’s easy!

Trust me, this class will be hard enough…don’t make it worse.