Chapter 1: The Science of Physics
 1.1 The Science of Physics
 1.2 Scientific Inquiry and Natural Laws
 1.3 The Nature of Scientific Knowledge
Chapter 1 Objectives
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Describe what physics is about.
Use the ideas of energy and electric current to explain how a battery
lights a bulb.
Explain how there can be many forces acting on an object that is not
moving.
Give examples of an oscillator and a wave.
Describe the physical differences, other than color, between blue light
and red light.
Give an example of how hot matter is different from cold matter.
Describe the process of inquiry and the relationship between inquiry
and learning physics.
Describe the difference between matter and energy.
Explain the relationship between a theory, a hypothesis, a natural law,
and an experiment.
Chapter 1 Vocabulary
 energy
 objectivity
 experiment
 process
 hypothesis
 repeatability
 inquiry
 scientific evidence
 matter
 theory
 natural law
1.1 The Science of Physics

Physics
provides
the in
foundation upon which
Biology:
everything
rests
the follows
human the
understanding
of other major
biology
laws of
areas
in science.
physics
 Chemistry: is the science of
matter and energy.
 Physics: provides the
ground rules for how matter
and energy behave.
1.1 A grand tour of physics
 What do nerves, cell phones, and lightning
have in common?
1.1 Matter and Energy
 Our universe is made of matter and
energy.
 Matter is “stuff” that has mass and takes
up space.
 Energy is the ability to make things
change.
1.1 Electricity and energy
 Energy is active.
 Things change by
exchanging and
transforming energy.
 Electricity is useful
because electrical energy
can easily be transformed
into many other kinds of
useful energy.
1.1 Energy
 Energy is the
fundamental
constituent of the
universe.
 Yet, in its pure form,
energy cannot be
tasted, touched, seen,
smelled, or heard.
1.1 Energy and joules
 All types of energy are
measured in tiny units
called joules.
 One joule is the amount
of energy it takes to raise
a pint of ice cream about
21 centimeters.
1.1 Energy and Electricity
 Electrical energy is carried by an electric
current.
 Electric current is measured in amperes, or
amps.
1.1 Energy and Electricity
 Electric current flows
in response to
differences in
electrical energy.
 Electrical energy is
measured in volts.
1.1 Energy and Electricity
 A regular alkaline battery has a
voltage of 1.5 volts.
 That means each amp of current
flowing through the battery
carries 1.5 joules of energy each
second.
 The electrical outlet on the wall
has an energy rating of 120 volts.
 That means each amp of current
carries 120 joules of energy each
second, which is one reason
outlets are more dangerous than
batteries.
1.1 Mechanics
 In physics, however, mechanics is the science
of forces and motion.
 Mechanics has two parts: dynamics and statics.
 Understanding motion is the dynamic part of
mechanics.
 Understanding why things stand still or break is
the static part of mechanics.
1.1 Force
 Mechanics starts with
the idea of force.
 A force is an action such
as a push or a pull.
 Your weight is a force
from the gravity of Earth
pulling on the mass of
your body.
 Forces are the cause of
action, even when
nothing is moving.
1.1 Newton’s first law
 Changes in motion such as
starting, stopping, turning,
speeding up, and slowing down
require forces.
 An object at rest stays at rest,
and an object in motion
continues in motion at the same
speed and in the same direction
forever.
 In theory, a kicked ball on a
level sheet of frictionless ice
would travel forever in a
straight line.
1.1 Equilibrium and statics
 In any normal situation there are always forces
acting, one of which is usually gravity.
 If nothing is moving, then physics tells us at
least two forces must be acting, with one
canceling the other.
 The forces are in equilibrium.
 This is true even when you don’t know about a
second force.
1.1 Equilibrium and net force
 If we use the value +2 to represent the force on
the right, then –2 represents the force on the
left.
 Adding +2 and –2 gives a total of zero or zero
net force.
 Cutting a string removes one force.
 The result is that the total or net force is no
longer zero, and the block moves.
1.1 Equilibrium and dynamics
 At the very instant the string is cut, the block is
not yet moving.
 It immediately starts moving but it starts from
rest.
 The force from the connected string
accelerates the block by causing its speed to
increase.
 Unbalanced forces cause objects to accelerate
in the direction of the force.
1.1 Harmonic Motion
 Compare a ball rolling downhill with a swing going back
and forth.
 The rolling ball is one kind of motion, with
characteristics of speed and position.
 The swing is another kind of motion because it repeats.
1.1 Oscillators
 A swing is an example of
an oscillator.
 An oscillator is an object
or system that repeats
over and over again in
cycles.
 Many examples of
oscillators occur in
nature and also in human
technology.
1.1 Frequency and cycle
 The frequency of a repeating motion is how
often it occurs in a given unit of time.
 A frequency of once per second means the
motion repeats once per second.
 A typical swing has a frequency of about of a
cycle per second.
 A cycle is a complete back-and-forth movement
of the swing.
1.1 Waves
 Waves carry information and waves carry
energy.
 A wave spreads its frequency wherever it
travels.
1.1 Sound
 Sound is a wave of air pressure.
 When a guitar string vibrates back and
forth, the soundboard of the guitar
pushes the air that touches it back and
forth.
 Like the water wave, that air pushes the
air next to it, which pushes the air next to
it, and so on, all the way to your ear drum.
1.1 Light
 Light is a very rapid wave of electricity and
magnetism.
 If you could move a magnet up and down 1
million times per second, you would have a
radio wave.
 Now imagine moving the magnet up and down 5
thousand trillion times per second (5 × 1015 Hz).
 You would make red light!
1.1 Light
 The colors between red and blue in the rainbow
represent the range of light energy that our
eyes can detect.
 However, light has an infinite range of energies.
1.1 Heat and Energy
 All matter contains heat energy.
 The higher the temperature, the more
heat energy there is.
 You put energy in to make something
warmer.
 You take energy out to make something
colder.
1.1 Heat and Energy
 Whenever anything gets warmer or
colder, energy is being exchanged.
 If you have 1 gram of water, adding 4.18
joules of energy makes the temperature
increase by exactly 1 degree Celsius.
1.1 Heat and Energy
 Many of the most
useful human
inventions
ultimately
transform heat into
other forms of
energy.
1.1 Heat and atoms
 In 1827, Scottish botanist Robert Brown noticed
that a speck of pollen floating in water moved
around in a jerky, and continuously agitated
way.
 Brownian motion comes from the impacts of
trillions of atoms, constantly moving and
jostling each other.
 Brownian motion is related to atomic motion,
which is dependent on temperature.
1.1 Heat and atoms
 Energy of motion is called
kinetic energy.
 Heat is actually kinetic
energy.
 The “feeling of heat” is the
energy moving between
more-energetic atoms to the
less-energetic atoms.
Chapter 1: The Science of Physics
 1.1 The Science of Physics
 1.2 Scientific Inquiry and Natural Laws
 1.3 The Nature of Scientific Knowledge
1.2 Discovering natural laws
 By clever thinking, over
thousands of years, humans
have deduced many of the
natural laws, often by trial and
error.
 Fortunately, nature is reliable
in that it always obeys the
same natural laws.
1.2 Scientific process
 The process of deducing the natural laws
includes:
 observation,
 experimentation,
 and analysis.
1.2 Scientific process
 Observation means looking at something that
happens in a careful way and recording all the
important details.
 An experiment is a situation set up specifically
to observe something, like the relationship
between applied force and the subsequent
motion of a cart.
 Analysis is the process of thinking about
observations to determine what they mean.
1.2 Hypothesis
 A hypothesis is a tentative explanation that can
be tested by an experiment or observation.
 A mature hypothesis successfully agrees with
every relevant detail of every observation or
experiment.
 The validity of a hypothesis improves as more
experiments are completed and analyzed.
1.2 Theory
 A theory is a
comprehensive, welltested explanation of how
and why a process in
nature works the way it
does.
 A theory that correctly
explains the first 1,000
experiments but fails to
explain the 1,001st cannot
be wholly complete.
1.2 Science and the
internet
 Beware of “science knowledge” found on the
Internet!
 Anyone can post on the internet, including
people who do not know, are misinformed, or
simply just want to advance their own, often
untested, hypotheses.
1.2 Scientific Evidence
 Good scientific evidence must pass the tests of
being both objective and repeatable.
1.2 Learning physics through inquiry
 Inquiry is a process of
learning by asking questions
and making observations
that allows you to deduce
answers and pose better
questions.
 Inquiry is a skill you use
every day. You continually
test your ideas against your
observations, and over time,
you develop understandings
about nature.
Chapter 1: The Science of Physics
 1.1 The Science of Physics
 1.2 Scientific Inquiry and Natural Laws
 1.3 The Nature of Scientific Knowledge
1.3 The nature of scientific knowledge
 Scientific knowledge grows by
systematically extending simple
explanations to include more complex
situations.
 Explanations can be qualitative or
quantitative and tell you why or how
much.
1.3 Models
 The most useful form of
scientific knowledge is a
model.
 One type of model is a
graph.
 This graphical model
shows how a rolling cart’s
speed changes as it goes
downhill.
1.3 Models
 The second form of simple model is a formula.
 Formulas are more powerful models than graphs
because they can include more than two
variables and have a much wider range of
values.
1.3 Models
 A model tells you precisely how the
variables in a system are related to each
other.
 A system is a group that we choose to
include all the variables we are interested
in that affect each other.
1.3 Problem Solving Techniques
 Step 1
 Determine what the problem asks you to find.
 Step 2
 Identify the information you are given.
 Step 3
 Identify laws or relationships.
 Step 4
 Apply the given information and the
relationships.
Calculating time from speed
and distance
 How long does it
take to travel 2,000
kilometers at a
speed of 100
kilometers per
hour?
Calculating time from speed
and distance
 Step 1
 You are asked to find time.
 Step 2
 You are given the distance in km and speed in km/h.
 Step 3
 Time is distance ÷ speed.
 Step 4
 Time = 2,000 km ÷ 100 km/h = 20 h
1.3 A good theory that started out
wrong
 An early theory of fire proposed that all materials
contained a substance called phlogiston, which was
released during burning.
 The careful work of Antoine Lavoisier (1743–1794) finally
disproved the phlogiston theory.
 Lavoisier showed that as a metal burned, it increased in
weight because it gained oxygen.
 While the phlogiston theory was not correct, it led to the
discovery of oxygen.
1.3 Scientific knowledge and the solar
system
Early civilizations
believed the Earth
was covered by a
dome on which the
sun, stars and
planets moved.
In the Middle Ages,
people thought the
sun, stars and
planets circled the
Earth.
Today we know the
earth and planets
orbit the sun.
BIOMIMICRY
 Scientists and engineers are
embracing the concept of
biomimicry by taking a hard look at
natural objects and organisms to
carefully study their structures,
behaviors, and the way they
organize as groups.
 The hook-and-loop fastening
Velcro, invented by George de
Mestral, has been used as a simple
fastening system by thousands of
people.