1. Review of Essential Skills:
Scientific Notation, Significant Figures & Conversions

2. SI Units
Standard Unit: Metric is usually the preferred unit in science.
Metric referred to as “S.I.” (System Internationale)
Also known as MKS system
Metres: Standard unit for distance
Kilograms: Standard unit for mass
Seconds: Standard unit for time
Some examples: Speed (m/s), Volume (m3)

3. Scientific Notation
Often in Physics, calculations require the usage of large figures, scientific notation makes these calculations easier.
Some examples:
m = x 107 m
s = x 10-5 s
Decimal moved left?
Positive Exponent
Decimal moved right?
Negative Exponent

4. Significant Figures (“Sig Figs”)
Values that are significant to a measurement.
Some examples:
Value
# of Sig Figs
Comment
32000 m 2
Last 3 zeros are place holders m 5
Last 2 zeros are place holders
15000 m 4
Tilde (~) implies answer accurate to tens (dm)
100.0 m m ~
Numbers recorded AFTER decimal place wouldn’t be recorded unless significant 4 5
Leading zeros not significant, last two digits are part of the measurement.
In General: Leading / trailing zeros are typically placeholders,
not part of the measurement itself.

5. Rounding Rules
Very simple set of rules with the exception of numbers terminating in 5
Rules:
Number terminates in value > 5: Round up
Number terminates in value < 5: Round down
Number terminates in 5:
Round to ensure the rounded value is an even number.

6. Eg.1: Round to the specific number of sig figs.
Since the last example is terminated by a non-zero number, the “5 rule” does not apply…
Value
Sig Figs to Round To
Answer
5.637 3
4.6337
3.65 2
3.55
3.5500
3.651
5.64
4.63
3.6
3.6
3.6
3.7

7. Eg.2: Consider the following data set: [1.5, 2.5, 3.5, 4.5]
Why the “5 rule”?
Automatically rounding up skews data in one direction.
Eg.2: Consider the following data set:
[1.5, 2.5, 3.5, 4.5]
Original sum: = 12
Rounding Rule for 0.5
Rounded Set
Sum
Round up
“5 Rule”
[2,3,4,5] 14
[2,2,4,4] 12

8. Conversions Done by a process called “multiplication by ones”.
Unwanted units cancel.
Eg.3: Convert 72 km/h to m/s
* One unit at a time

9. Eg.4: Convert 5 kg/m2 to g / km2