Units of MeasurementScience 9

September 2014

Vocab• Unit – a standard of measurement in which other

measurements are expressed.• English System (United States Customary System) –

system of measurement used in the US, includes inches, gallons, pounds, miles, etc.

• Metric System – system of measurement used in countries other than the US and by the scientific community; units are organized by factors of 10.

• Prefix – element placed at the beginning of a word that changes the meaning of the word; in the metric system, it indicates a unit smaller of larger than the basic unit by factors of 10.

Why is measurement

important?• Use it in daily life

– Cooking– Construction– Decorating a room– Driving

• Communication– Need to be able to communicate

measurements and distances to other people

Measurement & Physics

• Physicists try to find relationships between the quantities they measure use units of measurement to do this

• Measure the very largest and smallest things in the universe– Smallest: mass of an electron =

0.000000911 yg– Largest: light years (distances between stars

and galaxies

Units of MeasurementDistanc

eMass Time Area/

VolumeTemperature

inch milligram

hours in^2, in^3

Fahrenheit

meter ounces seconds m^2, m^3

Celsius

mile pounds days Liters Kelvin

feet gram months Galloncentimeter

kilogram

years Quart

millimeter tons minutes Pint

How to use a ruler:1. Determine if you are

measuring in centimeters or inches and find that unit’s side of the ruler.

inches

centimeters

How to use a ruler2. Place the “0” mark at one end of the

object you are measuring.

“0” mark

How to Use a Ruler3. Record the ruler marking that falls at

the other end of the objectFor INCHES: - Each dash after a whole inch is 1/16

of an inchFor CENTIMETERS: - Each dash after a whole centimeter is

1/10 of a centimeter

Measurement Lab

Relative SizeUnit Relative

SizeExamples

Inches 1 in Photo size, body parts

Feet 1 ft = 12 in Height of people, room size

Yard 1 yd= 3 ft Football field

Meters 1 m ~ 1 yd Height of people, track length

Kilometers 1km = 1000m Car travels, between cities

Centimeters 1 cm = 0.01 m

Paper, small machine parts, body parts

Millimeters 1 mm = 0.001 m

Coins

Two Main Systems of Measurement

• United States Customary System (USCS)

• System International (SI)- Metric System

USCS

• Used in the U.S. and Burma• Distance: inch (in), foot (ft), yard

(yd), mile (mi)• Mass: pound (lb)• Time: second (sec)• Temperature: degrees Fahrenheit

(F)

Metric System• Used by all other countries and the scientific

community• Units that are larger or smaller units than the

basic units are defined in multiples of 10

• Basic Units– Distance: meter (m)– Mass: gram (g)– Time: second (s)– Temperature: degrees Celsius– Volume: Litre (L)

Metric System: Prefixes

• Adding a prefix to a basic metric unit increases or decreases the unit size by a factor of 10

• Prefixes are always added to the beginning of Metric basic units

• For example,– centimeter (cm)– milliliter (ml)– kilogram (kg)

Metric PrefixesPrefix

Symbol

Relation to Basic Unit

milli- m 1000 mm = 1 m

centi- c 100 cm = 1 m

deci- d 10 dm = 1 m

deka- da 1 dam = 10 m

hecto- h 1 hm = 100m

kilo- k 1 km = 1000 m

Common Unit Equivalencies

• 1 m = 100 cm

• 1 m = 1000 mm

• 1 km = 1000 m

• 1 ft. = 12 in.

• 1 yd. = 3 ft.

• 1 min = 60 s

• 1 hr = 60 min

• 1 day = 24 hr.

• 1 year = 365 days

Conversion Hints• Staircase Method

Rules to using the Staircase Method of

conversion1. Find the unit on the staircase where

you are STARTING. ex. Convert 5 m = ________ cmYou are starting at m.

2. Count up or down the stairs ending on the unit you need to convert to. ex. 5 m = ________ cmYou need to convert to cm.

3. If you counted UP the stairs, move the decimal point LEFT.4. If you counted DOWN the stairs, move the decimal point RIGHT.

ex. 5 m = ________ cm

5 m = ______ cm

Move decimal 2 places to the right.

5 m = 500 cm

PRACTICE!!

• You will get a sheet to practice conversions.

• Use the staircase method (it is the easiest!)

• Do not be afraid to ask for help.