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Chapter 1
The Science of Physics
1-1: What is Physics?
We are surrounded by the principles
of physics in our everyday lives.
 Any problem or question that deals
with temperature, size, motion,
position, shape or color involves
physics.

The Areas of Physics:

Classical Mechanics
motion of macroscopic objects at low speeds
(v << c)
Examine motion & its causes. Ex:
falling objects, weight, friction, etc.

Thermodynamics
deals with heat,
work, temperature,
and the statistical
behaviour of a large
number of particles

Vibrations & Waves
Deals with specific
types of repetitive
motion.
Ex: springs,
pendulums, sound…

Optics
Deals with light and
its properties.
Ex: mirrors, lenses,
color…

Electromagnetism
theory of
electricity,
magnetism and
electromagnetic
fields
Ex: electric charge,
circuits, permanent
magnets

Relativity
motion of objects at any speed, including
very high speeds
Ex: particle collisions, nuclear energy

Quantum mechanics
theory dealing with
behaviour of
particles at atomic
levels
The Science of Physics
Electromagnetism:
Battery, starter, headlights
Optics:
Headlights,
rear-view
mirrors
Vibrations and
Mechanical waves:
shocks, radio speakers
sound insulation
Thermodynamics:
Heat and temperature
Efficient engines, coolants
Mechanics:
Spinning motion of the wheels,
tires that provide enough
friction for traction – all motions
Scientific Method




Make observations & collect data that lead to
a question.
Formulate and objectively test hypotheses by
experiment.
Interpret results, and revise hypothesis if
necessary.
State conclusions in a form that can be
evaluated by others.
Models in physics




A model is a replica or
description designed to show
the structure or workings of
an object, system or concept.
Simplify
Help build hypotheses
Guide experimental design
Make testable predictions
1-2: Measurement
Physical Quantity vs. Units


Physical quantity- any characteristics
of objects that can be measured.
Ex: length, mass, temperature
Units of measure- basic standards of
measurement
Ex: length can be measured in miles or
meters
SI Standards
UNIT
Original
standard
Current
standard
Meter
(length)
1/10,000,000
distance from
equator to North
Pole
Distance traveled
by light in a
vacuum in 3.3 x
10-9 s
Kilogram
(mass)
Mass of 0.0001
cubic meters of
water
Mass of a specific
platinum-iridium
alloy cylinder
Second
(time)
(1/60)(1/60)(1/24)
= 0.00001574
average solar
days
9,192,631,700
times the period
of a radio wave
from cesium-133
Other units are DERIVED units, that
is, they are calculated from
measurements in the base units.
 Examples are velocity (m/s),
acceleration (m/s2), or density
(g/cm3).

Prefixes
Symbolize powers of 10
 Used to accommodate very
large/small quantities
 Commonly used prefixes on table 1-3,
pg. 12

Conversions
Conversion factor- ratio used to
convert from one unit or prefix to
another
 Used in the factor-label method to
express answers in the desired units.
 Example:
1 mile = 1.61 km

» Example:
Convert 10.0 miles into kilometers
» Conversion factor: 1 mile = 1.61 km
Set up the conversion so that miles
cancel when multiplied
# km = 10.0 mi x 1.61 km = 16.1
1 mile
Sample Problem

“Oh man,” a bleary-eyed student once
noted, “That lecture on classroom
policies must have gone on for a
microcentury.” How many minutes are
there in a microcentury?
Solution

Micro = 10-6
 100 yr  365day  24hrs  60min 



1x10 century

 1century  1 year  1day  1hr 
 52.56min  50min
6
Accuracy & Precision


Accuracy- how close
a measurement
comes to accepted
value
Precision- degree of
exactness, small
variation between
repeated
measurements
Measurement / Significant figures



Uncertainty in measurement depends
on the quality of the apparatus, skill
of the experimenter and number of
measurements performed
Sig figs keep track of imprecision
Sig figs include all measured digits
plus one estimated digit

Sig Figs
11
10
10
11
12
12
10.3 : read as much
as you
can and estimate
one digit
10.30 : read as
much as you
can and estimate
one digit
The rules for significant digits
1. All whole number digits are
significant.
Ex. 1, 2, 3, 4, 5, 6, 7, 8, 9
245,955
14,328
96
6 significant digits
________________
________________
The rules for significant digits
2. Rules for Zeros
a. Zeros between other nonzero
digits are significant.
Example:
404
3 significant digits
40530004
_____________
606060606
_____________
The rules for significant digits
b. Zeros in front of nonzero
digits are not significant
 Example
 00222
3 significant digits
 0.00556 ______________
 00000000001 ____________
The rules for significant digits
c. Zeros that are at the end of a
number and also to the right of the
decimal are significant.
 Example
 120.00
5 significant digits
 4052.00000
______________
 30302.0
______________
The rules for significant digits
d. Zeros at the end of a number
without a decimal are not
significant.
 Example
 300
1 significant digit
 46000
______________
 460.00
______________
The rules for significant digits
in calculations
1. Addition or subtraction - The
final answer should have the
same number of digits to the
right of the decimal as the
measurement with the smallest
number of digits to the right of
the decimal.
Example
 4.02 + 6.11+ 4.9 = 15.0 (15.03)
 6.111
+ 12.31 + 1.2 = _________
 10.256
– 2.44 – 1.6 = ________
The rules for significant digits
in calculations
2. Multiplication or division –
the final answer has the
same number of significant
figures as the measurement
having the smallest number
of significant figures.
Example
4.0 x 2.11 x 3.456 = 29
(actual answer is 29.16864)
4.01 x 4.1 / 4.012 = _______
16.211 / 4.211 / 2 = _______
Scientific Notation



Scientific Notation- in the form of A
x 10 n
1< A< 10 and n = power of 10
A contains only sig figs of original
number/measurement
1-3: Language of Physics
Tables, Graphs, & Equations
Tables, graphs & equations make data
easier to understand
 Equations used to describe relationship
between physical quantities
 Appendix B pg 952-960 lists variables,
symbols & constants used

Dimensional Analysis


Dimensional analysis used to:
- check a specific formula
- give hints as to the correct form the
equations must take
Dimensional analysis does not give any
information on the magnitude of the
constants of proportionality
Orders-of-Magnitude
Refers to the nearest power of 10
 Useful to compute an approximate
answer
 Results can be used to decide whether
a more precise calculation is
necessary
 Assumptions are usually needed
