2. Measurement and Units
• Math - the language of Physics
• SI Units – International System
– MKS
•Meter: m
•Mass: kg
•Time: s
• National Bureau of Standards
• Prefixes
3. SI Unit Prefixes - Part I
Name Symbol Factor
tera- T 1012
giga- G 109
mega- M 106
kilo- k 103
hecto- h 102
deka- da 101
4. SI Unit Prefixes- Part II
Name Symbol Factor
deci- d 10-1
centi- c 10-2
milli- m 10-3
micro- μ 10-6
nano- n 10-9
pico- p 10-12
femto- f 10-15
5. The Seven Base SI Units
Quantity Unit Symbol
Length meter m
Mass kilogram kg
Temperature kelvin K
Time second s
Amount of
Substance
mole mol
Luminous Intensity candela cd
Electric Current ampere a
6. Derived SI Units (examples)
Quantity unit Symbol
Volume cubic meter m3
Density kilograms per
cubic meter
kg/m3
Speed meter per second m/s
Newton kg m/ s2
N
Energy Joule (kg m2
/s2
) J
Pressure Pascal (kg/(ms2
) Pa
7. SI Unit Prefixes for Length
Name Symbol Analogy
gigameter Gm 109
megameter Mm 106
kilometer km 103
decimeter dm 10-1
centimeter cm 10-2
millimeter mm 10-3
micrometer μm 10-6
nanometer nm 10-9
picometer pm 10-12
8. Scientific Notation
M x 10n
• M is the coefficient 1<M<10
• 10 is the base
• n is the exponent or power of 10
9. 5.45E+6 or 5.45 x 10^6
Numbers less than 1 will have a negative
exponent.
A millionth of a second is:
0.000001 sec 1x10-6
1.0E-6 1.0^-6
10. Factor-Label Method of Unit Conversion
• Example: Convert 5km to m:
• Multiply the original measurement by a
conversion factor.
NEW UNIT
85km x 1,000m = 85,000m
1km
OLD UNIT
11. Factor-Label Method of Unit Conversion:
Example
• Example: Convert 789m to km:
789m x 1km =0.789km= 7.89x10-1
km
1000m
12. Convert 75.00 km/h to m/s
75.00 km x 1000 m x 1 h___ = 20.83m/s
h 1 km 3600 s
14. • Accuracy - a measure of how
close a measurement is to the
true value of the quantity being
measured.
15. Example: Accuracy
• Who is more accurate when
measuring a book that has a true
length of 17.0cm?
Susan:
17.0cm, 16.0cm, 18.0cm, 15.0cm
Amy:
15.5cm, 15.0cm, 15.2cm, 15.3cm
16. • Precision – a measure of how
close a series of measurements
are to one another. A measure of
how exact a measurement is.
17. Example: Precision
Who is more precise when measuring
the same 17.0cm book?
Susan:
17.0cm, 16.0cm, 18.0cm, 15.0cm
Amy:
15.5cm, 15.0cm, 15.2cm, 15.3cm
19. Example: Evaluate whether the
following are precise, accurate or
both.
Accurate
Not Precise
Not Accurate
Precise
Accurate
Precise
20. Solving Word Problems
• Analyze
– LIST KNOWNS AND UNKNOWNS.
– Draw a diagram.
– Devise a plan.
– WRITE THE FORMULA OR EQUATION TO BE USED.
• Calculate
– SUBSTITUTE THE KNOWNS WITH UNITS IN THE EQUATION
AND EXPRESS THE ANSWER WITH UNITS.
– If needed, rearrange the equation to solve for the unknown.
• Evaluate
– Is the answer reasonable?
21. General Physics 1 Problem Solving
(Quarter 1)
1.Given
2.Formula or Equation
3.Plug in/substitute the values
4.Box the final answer
