Holt, Physics Chapter Summary
Chapter 1: The Science of Physics
Section 1: What is Physics?
The goal of physics is to use a small number of basic concepts, equations, and
assumptions to describe the physical world.
Example: We can use the same physics to describe a satellite orbiting the Earth as we
can to describe the interaction between two planets.
Physicists study physics to help describe the world around them. Physics also makes the
inventions, appliances, tools, and building we live in possible. Without physics, it would
feel like we were living in the stone age.
From life experiences, we know a lot about physics. We know what will happen if we
leave a piece of ice out on a hot day.
Areas within Physics
Name
Mechanics
Thermodynamics
Vibrations and Waves
Optics
Subjects
Motion and its causes,
interactions between objects
Heat and temperature
Specific types of repetitive
motions
Light
Electromagnetism
Electricity, magnetism, and
light
Relativity
Particles moving at any
speed, including very high
speeds
Behavior of submicroscopic
particles
Quantum Mechanics
Examples
Falling objects, friction,
weight, spinning objects
Melting and freezing
processes, engines,
refrigerators
Springs, pendulums, sound
Mirrors, lenses, color,
astronomy
Electrical charge, circuitry,
permanent magnets,
electromagnets
Particle collisions, particle
accelerators, nuclear energy
The atom and its smallest
parts
The Scientific Method
1.
2.
3.
4.
Make observations and collect data that lead to a question
Formulate and objectively test hypothesis by experiments.
Interpret results, and revise the hypothesis if necessary.
State conclusions in a form that can be evaluated by others.
Models – Explain the most fundamental features of various phenomena.
Holt, Physics Chapter Summary
Example: If we model a ball, we can observe the ball’s surroundings, size, spin, weight,
color, time in air, speed, and sound.
System – a physicist chooses which area to study in a complicated situation to simplify
the situation.
We can model the ball with a computer model and define our system as only the path of
the ball.
Hypothesis – a reasonable explanation for observations – one that can be tested with
additional experiments.
Example: Galileo first hypothesized that lighter objects would fall slower than heavier
objects. He ran experiments and found that they actually fall at the same rate. He
reformulated his hypothesis and then ran more experiments to test his hypothesis.
Controlled Experiment – In order to test a hypothesis, you must change only one
variable at a time to determine what is affecting your observations.
If the model is good enough, we can make predictions from the model.
Section Review Answers (pg. 9):
1. Mechanics, thermodynamics, vibrations and waves, optics, electromagnetics,
relativity, and quantum mechanics.
2. a. mechanics
b. thermodynamics
c. vibration and waves
d. electromagnetics
e. optics
3. Observation, collect data, ask question, formulate and test hypothesis, interpret
results, state conclusions.
4. Design of a car or computer model of ball in motion (endless answers)
5. a. mechanics
b. thermodynamics
c. electromagnetics
Section 2: Measurements in Experiments
Measurements – can represent the physical quantity of length, mass, time, etc., with
specific standard unit of measurement.
It’s important to recognize that when you are measuring, you have recognize what you
are measuring and also what unit you are using to measure.
SI is the standard measurement system for science. In 1960, an international
committee agreed on a system of standards.
Holt, Physics Chapter Summary
SI Units:
Length (Meter)
Mass (Kilogram)
Time (Seconds)
Cubit – was the standard measurement in Greek times. A cubit is measured as the length
of the forearm.
SI uses prefixes to accommodate extremes. We may need to measure something very
large or very small so we use prefixes to symbolize the power of 10.
Metric Unit Prefix
Prefix
Exa
Peta
Tera
Giga
Mega
Kilo
Hecto
Deka
Deci
Centi
Milli
Micro
Nano
Pico
Femto
Atto
Abbreviation
E
P
T
G
M
k
h
da
d
c
m
μ
n
p
f
a
Value
1018
1015
1012
109
106
103
102
101
10-1
10-2
10-3
10-6
10-9
10-12
10-15
10-18
It is very important that units of measurement agree.
Example: If you are measuring the area of a room, you’d measure the length and width
in feet. You can’t measure the length in centimeters and then the width in feet to find the
area.
Practice A Answers:
1. 0.000050m or 5E-5m
2. 0.000001s or 1E-6s
3. a. 0.000000010m
b. 0.000010mm
c. 0.010µm
4. 1.5E8 m
5. 1.440E6 kg
Holt, Physics Chapter Summary
Accuracy and Precision
Uncertainty – a numerical measure of confidence in a measurement or result.
Accuracy notes:
Experimental work is never free of error, but scientists try to minimize the error in order
to obtain accurate results.
Scientists also try and standardize testing procedures because if we use different methods
to try and obtain the same measurement, it may result in something called method error.
Scientists can also encounter something called instrument error when the instrument
being used is damaged in some way.
Example: A meterstick is damaged or worn on one end.
Accuracy comes down to how well the person makes the measurement. If we have a
standard or accepted value, we can compare our experimental results to the standard
using the percent error formula.
Percent error = (experimental value – actual value)/actual value x 100%
Precision notes:
Precision describes the limitations of the measuring instrument.
Example: A measurement of 1.325 m is more precise than a measurement of 1.3 m.
Scientists can improve upon the precision of an instrument by making a reasonable
estimation between the marks on the instrument. Generally this estimation would also
include an estimated uncertainty.
Example: If a ruler is precise to the nearest centimeter and you make a reading of 18.2
centimeters, you are making a reasonable assumption to the nearest millimeter. The
estimated uncertainty would be +/- 1mm.
Significant Figures – a number that is reported to a specific number of digits to represent
the amount of precision in the measurement.
Each measurement can only have one estimated digit when it is reported with significant
figures.
Please see the book (pg. 18-19) or the Rules of Significant Figures handout for more
detail.