1. You have two buckets - one holds exactly 5 gallons and the other 3 gallons How can you measure out exactly 4 gallons of water? (Assume that you have an unlimited supply of water and that there are no measurement markings of any kind on the buckets.)

2. You have two buckets - one holds exactly 5 gallons and the other 3 gallons How can you measure out exactly 4 gallons of water? (Assume that you have an unlimited supply of water and that there are no measurement markings of any kind on the buckets.)
1) Fill the 3-gallon bucket, dump it into the 5-gallon bucket 2) Fill the 3-gallon bucket, fill the 5-gallon, leaving 1 gallon left in the 3- gallon bucket 3) Empty the 5-gallon bucket 4) Dump the 1 gallon from the 3-gallon bucket into the 5-gallon bucket 5) Dump one full bucket from the 3-gallon bucket on top of the 1 gallon in the 5-gallon bucket You're left with four gallons of water in the 5-gallon bucket.

4. Units System
In Physics (or any science) a number without a unit can be meaningless. We will commonly use the SI units MKS Unit system in stead of the English System.
Measurement
Unit
Abbreviation
Length
Meter m
Mass
Kilogram kg
Time
Second s
Force
Newton N
Energy
Joule J

5. The Metric System
The metric system works in multiples of tens. Each multiple of 10 is 1 order of magnitude. By changing the order of magnitude you can change the units associated with it.
If our base unit is the Gram (g), then 1 kilogram (kg) is 1000 times larger than one gram. OR
It takes 1000 grams to equal 1 kilogram.
Prefix
Abbreviation
Factor
Mega M
( )
Kilo k
(1000)
BASE UNIT
Centi c
(0.01)
Milli m
(0.001)

6. The Conversion Factor If I have 3245g, how many kilograms do I have?
Here we can use a Conversion Factor
Since 1000g = 1kg I can create a ratio of the two numbers that equals 1, this is the Conversion Factor

7. The Conversion Factor
Now I multiply the value I am trying to change by the conversion factor
Unit you want to change to
Unit you want to get rid of
*Note: This is really just rearranged proportion
Proportional Relation

8. Unit Conversions
cm-in ( 1 in = 2.54 cm) How many seconds are there in a day

9. Metric Conversions Convert: 28km to cm 50g to kg
How many kilograms are there in 5 grams

10. Changing From English to Metric
How fast is 60 miles/hour in meters/sec?
To do this you must change miles into meters using a conversion factor and hours into seconds using a separate conversion factor.

11. Conversions
Convert 52 km/hr into m/sec How many miles can a car get on 5 gallons of gas if its fuel consumption is 25 mi/gal Convert 20 m/s to mi/hr

12. Significant Figures
Why do we use them?

13. Significant Figures

14. Significant Figures Rules

15. Examples
How many Significant Figures are there in the following?