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Grade 11 Physics

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Lukas Notten

on 21 July 2017

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Transcript of Grade 11 Physics

Grade 11 Physics
SPH 3U - Road Map
Kinematics
Dynamics
Electricity & Magnetism
Physics
What is physics?
Why study it in high school?
April Fools?
"Space is Hard"
Spot the physics...
http://nigelstanford.com/Cymatics/
Taking the magic out of life?
The big and the small
Richard Feynman
The most astounding fact
Neil deGrasse Tyson
https://www.quantamagazine.org/20150803-physics-theories-map/
A theory of everything?
The Higgs Boson
Hard Questions
Unit 1
Unit 2
Unit 5
Waves & Sound
Unit 4
1.1
Distance, Position & Displacement
1.2
Speed & Velocity
1.3
Acceleration
1.4
Uniformly Accelerated Motion
1.5
Motion in 2
Dimensions
1.6
Projectile
Motion
Describing
how
things move

Describing
why
things move

B. Scalars and Vectors
C. Describing location
Direction
= Distance
= Displacement
= Position
d
d
Δd
distance and direction from a reference point
change in position of an object
(or Position from Point A)
https://uniformmotion.bandcamp.com/releases
C. Average
Speed
and
Velocity
B. Uniform Motion
Instantaneous Velocity
1. Spot the differences!
2. Units?
You are at school. You decide to walk 500m [E] to the mall and then 1200m [W] home. The trip takes 30 minutes.
a) What is your average
speed
? (in m/s)
b) What is your average
velocity
? (in m/s)
Try it!
A. Velocity
Look familiar?
Position-time graphs
= slope of tangent on position-time graph
31 m/s
2
3.8 m/s
Jaguar XK8 (2001)
0-60 mph 7.0 seconds
2
Up to 41 m/s
2
A. Acceleration
B. Relationships in Motion Graphs
Galileo's Hypothesis
All objects fall with the same acceleration, regardless of mass (in a vacuum)
Myth 1
Myth 2
An object dropped and launched horizontally from the same height will hit the ground at the same time
Myth 3
An object can be launched backward from a moving vehicle so it falls straight down
Mythbusters: Gravity
Assignment:

Make a video to prove one of the above myths using material you can find in the classroom
You will be marked out of 4 in each of the following categories:
Video explains the myth in an a way that is easy to understand (ELI5)
Video demonstrates the physics of the chosen myth
Conclusion from experiment is clear
Group worked well together, all members involved
A. Uniformly Accelerated Motion
B. The "BIG 5" Equations of Motion
C. Gravity
These equations are to be used ONLY with uniformly accelerated motion
1) Constant Speed
2) Constant Direction
The Band!
motion with a constant acceleration
(magnitude + direction)
a special case of uniform acceleration
9.81 m/s
2
at sea level on earth
[9.80678 in Toronto according to Wolfram Alpha]
g=
Acceleration due to gravity
Free fall
when the only force acting on an object is gravity
[down]
->
Myth 4
A penny dropped from the observation deck of the CN tower will kill somebody on the ground if it hits them.
A. Drawing Scale Diagrams
to estimate resultant displacements and velocities
Direction
Scale
Resultants
[E 60˚ N]
when adding vectors, join them tail to tip
the vector from the beginning to the end of the path is called the resultant
include a magnitude AND direction!
choose a scale factor that is reasonable for the paper you are using
scale factor = scale distance/actual distance
to find how long to scale a distance to, multiply the actual distance by the scale factor
directions should always be taken from east or west
B. Adding Vectors Algebraically
(for perpendicular vectors)
C. Adding Vector Components
(for non-perpendicular vectors)
1. Join vectors tip to tail and draw the resultant vector
2. Calculate the magnitude of the resultant with the pythagorean theorem
3. Calculate the direction of the resultant with the arctan function (tan inverse)
1. Break down the given vectors into x and y components
2. Sum the x and y components to determine the resultant vector
3. Calculate the magnitude of the resultant with the pythagorean theorem
4. Calculate the direction of the resultant with the arctan function (tan inverse)
Analyze like a right angle triangle!!
Break it down... into components
Any vector can be broken down into its x and y components using sine and cosine:

In this course, there are 3 main ways to analyze motion in 2 dimensions:
ESTIMATE
ACCURATE (for non-perpendicular vectors)
ACCURATE (for 2 perpendicular vectors only)
we can extend this to any number of non-perpendicular vectors
Remember:
you can add vectors in any order!
2.2
Newton's First Law: Inertia
A. How to fix a hammer...
What is the best way to fix a hammer with a loose head?
B. Inertia
D. Moment of Inertia
C. Newton's First Law of Motion
Things like to keep doin' what they're doin'!
An object at rest will stay at rest unless acted upon by an external force
An object moving at a constant velocity will stay moving at that velocity unless acted upon by an external force
http://www.wired.com/2015/09/simple-physics-project-thatll-show-inertia-works/
an object's resistance to changes in motion
or how badly an object wants to stay still or keep moving
directly related to an object's
mass
What happens on the subway if you aren't holding on to anything when it stops?
What do you feel when you go around a corner in a car?
What happens when you quickly yank a tablecloth out from under a fully set table?
an object's resistance to rotation
What can you do to increase or decrease your moment of inertia?

How do cats flip over when dropped?
F
net
= sum of all forces acting on an object
We can check if the object is experiencing an external force by checking if the net force acting on the object is 0.
2.3
Newton's Second Law: F=ma
A. Newton's Second Law
An object with a net force will accelerate in the direction of the force in proportion to the magnitude of the force and inversely proportional to the mass of the object.
OR...
F = ma
net
net force
mass
acceleration
B. Newton's Second Law and Acceleration Due to Gravity
Remember our equation for the force of gravity?

Check it out! It comes from Newton's second law when acceleration is replaced with 'g' or acceleration due to gravity.
F = ma
net
F = mg
g
If the force of gravity acting on heavy objects is larger, then why don't they accelerate faster according to F=ma??
2.4
Newton's Third Law: Action-Reaction
A. Newton's Third Law of Motion
For every force, there is an equal and opposite reaction force
B. Action-Reaction Pairs
You are sitting in a sailboat in the middle of the ocean. There is no wind. If you blow on the sail will you go forward?
Strong Nuclear Force
Weak Nuclear Force
Gravity
Electromagnetism
What is a force?
The Four Fundamental Forces
2.1
Forces
A. Free Body Diagrams
B. Measuring Forces
1 N = 1 kg•m/s
2
keeps quarks together in protons and neutrons and creates the shape of atomic nuclei
responsible for radioactive decay (protons become neutrons and vice versa)
attractive force between everything with mass. dominates on the large scale
electrostatic and magnetism forces (which are two sides of the same coin)

the study of
why things move
Complicated version of what
touch
is:
So which of the fundamental forces are responsible for the regular push and pull forces??
System Diagram
-sketch of a situation
Free Body Diagram (FBD)
-object is isolated
-only forces are shown
This is just a simplified FBD where the person has been simplified as a point!
C. Net Force
the vector sum of all forces acting on an object
F
net
If an object is at rest, the net force acting on the object must be equal to 0.
F = 0
net
The Newton
The Force of Gravity
F = mg
g
F
air
F
f
F
g
F
N
F
app
2.5
The Force of Gravity
Uniform Motion
Uniformly Accelerated Motion
Motion in 1 Dimension
Motion in 2 Dimensions
constant speed
constant direction
constant change in speed
constant direction
2 Main Types of Motion
(for this course)
forces are measured in Newtons
In a frictionless world, the third ball would go on forever because of its
inertia
Galileo
1600's
Principia (1687) formalizes the works of Galileo and others before him.

"If I have seen farther it is by standing on the shoulders of giants."

Newton
1687
2.7
A Theory of Everything
If I have a mass of 75 kg
a) What is the force of gravity I exert on the ground?
b) What is the normal force?
c) Draw a FBD
Example:
IMPULSE
A bit of a summary:
FBD
note: this ground shouldn't be here for a proper FBD
Major League baseballs have an average mass of 5.125 ounces, and a 90-mph fastball can leave the bat at 110 mph. Extrapolating Newton's second law of motion, Russell determined that, in a collision lasting less than one-thousandth of a second, the average pro swing imparts 4145 pounds of force to the ball. Peak forces exceed 8300 pounds -- enough to stop a Mini Cooper, rolling at 10 mph, in its tracks.
note:
1 lb = 4.45 N
1 mi/h = 0.447 m/s
1 oz = 28.3 g
http://www.popularmechanics.com/adventure/sports/a4569/4216783/
Baseball Physics
Slow-mo weirdness
The Bricklayer's Lament
http://www.wired.com/2015/11/ballistic-pendulums-are-as-awesome-as-they-sound/?mbid=social_twitter
http://nautil.us/issue/29/scaling/will-quantum-mechanics-swallow-relativity
https://www.quantamagazine.org/20150803-physics-theories-map/
Newton's Law of Universal Gravitation
How is gravity proportional to mass? distance?
Calculate the gravitational field strength (g) for the surface of earth
What is the difference between
mass
and
weight
?
Around 1600 AD
Johannes Kepler
B. What is gravity?
Some gravity questions...
2.6
Friction
A. Coefficients of Friction
μ
K
μ
S
coefficient of kinetic friction
coefficient of static friction
force that resists objects sliding against each other
Car tires...
Static or kinetic friction?
**values can be found on page 170
F
K
F
N
___
=
F
S
F
N
___
=
Increasing Friction
Decreasing Friction
Ball bearings...
How do they work?
What are some other ways to decrease friction?
Which tire would provide the car with the most friction?
Why do tires have treads? (or grooves)
What's the deal with F1 tires?
B. Engineering Friction
But why? Why is friction for objects that are stopped different from objects that are stationary?
A. Newton got it wrong?
B. Classical and Modern Physics
C. A Theory of Everything?
Will Physics explain everything???
What did Newton get wrong?
Is what Newton discovered still useful?
Relativity and Quantm Mechanics
Uniting the 4 forces?
Energy
Unit 3
Gravitational
Sound
Kinetic
Electrical
Chemical
Mechanical
Nuclear
Thermal
Elastic
Radiant
potential energy
potential energy
energy
energy
energy
energy
potential energy
energy
energy
energy
3.3
3.4
3.5
3.6
3.1 Work
work is a force applied to an object over a distance
Why 'potential'?
What is an elastic object?
What is a spring?
3.2 Energy
Energy Transformations
energy is the capacity do do work
anything that can apply a force over a distance contains energy
lets explore the different types of energy we'll be working with...
the energy of moving objects
examples: a person running, a crash cart moving at a constant velocity, a particle being accelerated by the LHC
Energy cannot be created or destroyed, it can only be changed from one form into another
The total amount of energy in the universe is conserved (stays the same)
B. The Law of Conservation of Energy
potential energy stored as a result of an elastic object being stretched or compressed
examples
: pulling a rubber band, jumping on a trampoline, stretching or compressing a spring
the energy held by an object in relation to a mass's gravitational field
examples: lifting an object, moon (with respect to earth), comet, planets
total amount of kinetic and potential energy that the atoms or molecules in a substance has
examples: sun, stove, fire, rubbing hands together
the energy from electromagnetic waves that travel through space
examples: solar energy, light bulbs, phone screens, UV rays
energy released during fission or fusion, found in the core of an atom
examples: nuclear power plant, core of the sun, nuclear bomb
energy absorbed or relased in a chemical reaction
examples: leaves in sunshine, gas before ignited, wood before it burns, explosions
Conclusions from spring lab:
1) How does the work put into the spring by the masses compare to the energy gained by the spring?
2) Why is a force-displacement graph useful?
3) When can we not simply use W=Fd to calculate work?
energy due to an object's motion (kinetic) or position (potential) energy
sum of kinetic and gravitational potential energy together
examples: wrecking ball, bowling ball with pins, flying aircraft
3.7 Power
3.8 Efficiency
3.9
3.10
Which do you have a better chance of surviving?
1) Crashing into a brick wall at 100 km/h or
2) Two cars crashing into each other. Both cars are moving at 50 km/h toward the other
Which ball will be going faster when it reaches the bottom?
Different paths to the bottom...
Conclusions?
The rate at which work is done
Units:
1 J/s = 1 W
The Watt
make sure your units are in joules and seconds to end up with Watts
1000 W = 1kW
Remember...
Another unit for energy: the kWh
When dealing with electricity, we often refer to energy in terms of kWh (kilowatt hours) instead of Joules
when calculating kWh make sure your units are kW and h!
What is the conversion between MJ and kWh?
What is considered 'useful energy output' in each of these cases. What is not useful?
25-30%
1.5-2.5%
7-10%
useful energy output

energy input
Energy is always conserved, but then why doesn't a bouncy ball bounce to the same height when dropped?
Draw the energy transformations!
Power Generation
The Mix
Ontario's Current Energy Mix
http://www.ieso.ca/Pages/Power-Data/Supply.aspx
1) What energy transformations are involved in each type of electricity production?
2) What are some other ways we get energy besides the generation of electricity?
3) Renewable vs. Non-Renewable: What are they and why is non-renewable so popular?
EROI
Energy Return on Investment
A. Thermal energy, heat and temperature
What do you feel?
Heat, temperature or thermal energy?
What's going on??
1) Thermal Energy

2) Heat

3) Temperature
total kinetic and potential energy of the particles in a substance
the
transfer
of thermal energy from one substance to another
transfer is always from warmer to colder
measure of the average kinetic energy of the particles in a substance
How cold can it get?
How hot can it get?
B. Heat Transfer
1) Conduction
2) Convection
3) Radiation
There are 3 main ways thermal energy can be transferred between substances:
transfer of heat through contact of molecules
transfer of heat by circulating fluid particles
transfer of energy through electromagnetic waves
Absolute Zero = -273.15˚C
C. States of Matter
Do we glow?
http://www.livescience.com/7799-strange-humans-glow-visible-light.html
A. Mass-Energy Equivalence
Law of Conservation of Mass-Energy
Mass can transform into energy and energy into mass such that the total mass-energy in an isolated system remains constant.
or...
where c is the speed of light (3.0(10^8)m/s)
1) If you converted 1kg of mass to energy, how much energy would be produced?
2) How long would a 40W light bulb last on that amount of energy?
B. Fission and Fusion
Nuclear Fission
Nuclear Fusion
decomposition of large unstable nuclei into smaller more stable nuclei
nuclear reactors operate on chain reactions
why is uranium used?
fusing of nuclei of two atoms to make a larger nucleus
why is fusion so hard??
C. Radioactive Decay
4.1 What is Sound?
4.2 Describing Waves
4.3 Wave Interference
https://phet.colorado.edu/en/simulation/wave-on-a-string
Interactive Wave Simulation
4.7 How do we hear?
http://audacityteam.org/
Audacity
http://www.spacex.com/falcon9
Electricity
5.1
What is it?
Current Electricity
Static Electricity
Electric Potential Difference (V)
Current Electricity
5.2
Ohm's Law
5.3
Moving Charges
Charges at Rest
http://skullsinthestars.com/2012/11/26/more-on-franklin-and-the-electrical-kite-1752/
Benjamin Franklin
lightng is electricity?
gave us the lightning rod
Alessandro Volta
produce current electricity
voltaic cells
Charles-Augustin de Coulomb
interaction between charged particles
Andre-Marie Ampere
Energy per unit charge (V=E/Q)
Units:
Volts (V)
1 Volt = 1 J/C
Measured with a Voltmeter
Charge (Q)
Units:
Coulomb (C)
1 Coulomb = the charge of 6.242×10^18 electrons (-) or protons (+)
Like charges repel, opposite charges attract
Electricity is...
a force caused by electric charge
electric charges are due to electrons and protons
What is more dangerous, amps or volts?

How fast do electrons typically move along in a wire?
The flow of electrons, I = Q/t
Unit:
Amperes (A) or Amps
1 Amp = 1 Coulomb/second
Measured with an ammeter
We consider conventional current flow to be positive (not electron flow)
What are the advantages and disadvantages of AC and DC?
Current (I)
AC & DC
Circuits
5.5
Series Circuits
Parallel Circuits
Kirchhoff's Laws
Electromagnetism
5.6
build up of charges in a material
when there is enough potential difference, there is a static discharge (current)
Charges move (flow) in a wire or other material
E=QV
E=mgh
To get water to move, you need to have a height difference.
This gives it gravitational potental energy.
To get charges to move, you need to have a _____________.
This gives it electrical energy.
How do we get charges moving?
A measure of how difficult it is for electricity to flow through a material
Unit: Ohms
Measured with an ohmmeter
Resistance causes energy to be lost, usually in the form of heat
Resistance (R)
You can plot the values to determine the relationship between potential difference and current
Do all materials follow Ohm's Law?
A. Ohm's Law
The ratio of electrical potential difference across a resistor to the current is constant
The value of the constant ratio is the resistance
If a toaster produces 12 ohms of resistance in a 120 V circuit, what is the amount of current in the circuit?

Example:
2 main types of electrical circuit:
One path for the current
If one bulb goes out, they both go out
Multiple paths for the current
If one bulb goes out, the other stays lit
How can we calculate the resistance when there is more than 1 resistor in a circuit?
1. Kirchhoff's Current Rule:
The total current into a junction must be equal to the current out of a junction

2. Kirchhoff's Voltage Rule:
The total sum of the potential rises must equal the sum of the potential drops in a circuit
B. Total Resistance
A. Types of Circuit
Complex Circuits
Elements of both types of circuits
reduce each portion of the circuit one at a time
use Ohm's law with Kirchhoff's laws to analyze
Analyzing Complex Circuits
Electrical Power
5.4
Remember, power is defined as the amount of energy used or transformed per unit time.
Electrical Power
is the rate that electrical energy is used or transformed.
We can combine our definitions of current, electrical potential and Ohm's Law to derive 3 equations for electrical power

Recall:
we can rearrange P=E/t into E = P x t
if we input power as kW and time as hours, we can calculate energy in terms of kWh
a rough estimate of the cost of electricity is 10 cents/kWh
How many lightbulbs?
Kilowatt-Hours
A. Position
Activity: analyzing position with Algodoo
position is a way to describe the location of an object from a reference point
it is a vector quantity
position-time graphs are used to describe how an object's position changes over time
d
at reference point
to the east of reference point
to the west of reference point
moving away (east) from reference point with constant speed
moving towards (west) reference point with constant speed
increasing speed
decreasing speed
path along which an object travels
Δd = d - d
f
i
v
Using a position-time graph, describe the motion of an object:
the rate of change of an object's position
a vector quantity
can be described using velocity-time graphs
Activity: analyzing velocity with Algodoo
Using a velocity-time graph, describe the motion of an object:
You are at school. You decide to walk 500m [E] to the mall and then 1200m [W] home.
a) What is your distance traveled?
b) What is your total displacement?
Try it!
at reference point
to the east of reference point
to the west of reference point
moving away (east) from reference point with constant speed
moving towards (west) reference point with constant speed
increasing speed
decreasing speed
constant velocity
And since velocity is a vector, an object experiencing uniform motion
must have:
D. Relating Motion Graphs
The slope of a position-time graph is equal to the velocity
The area under a velocity-time graph is equal to the distance traveled
Velocity-time graphs
the rate of change of an object's velocity
a vector quantity
can be described using acceleration-time graphs
Activity: analyzing acceleration with Algodoo
Using an acceleration-time graph, describe the motion of an object:
at reference point
to the east of reference point
to the west of reference point
moving away (east) from reference point with constant speed
moving towards (west) reference point with constant speed
increasing speed
decreasing speed
How are velocity-time graphs related to acceleration-time graphs?
Steps for solving uniform acceleration problems:
1. Given: Write down values given in question, establish positive directions
2. Find: Identify which variable you are solving for
3. Solution: Identify which equation contains the appropriate variables
4. Isolate the variable you are trying to solve for
5. Plug and play! (make sure units are compatible)

Classical & Modern Physics
Juno
Significant Figures and Rounding
express answers in scientific notation when it's quicker than writing out the number
you may also use metric prefixes to express a final answer when it's convenient
you should be able to convert units within the metric system
Scientific Notation and Prefixes
Given
: state given values with units and appropriate variables, convert units as necessary *** always include a diagram if you're not given one ***
Find
: list the variable you need to solve for
Solution
: rearrange equations and solve for variable
Problem Solving Method
Solve for n
Solve for V
Rearranging Equations
You can often simplify calculations by rearranging equations before plugging in numbers
round the final answer to the number of significant digits that has the
least amount of significant digits in your calculation
when in doubt, round to 3 significant figures
only round your final answers, carry extra digits through calculations and perform as few separate calculations as possible
60˚
[N 30˚ E]
or
Would headlights work at the speed of light?
Relative Motion
is this the whole story?
is there a speed limit?
The action and reaction forces are called action-reaction pairs
ALL forces require an action-reaction pair
The action and reaction forces are must be applied to different objects, so 2 FBD's are required to show both forces
Draw FBD's to show the action and reaction forces for each of the images
Compare the forces:
Brainstorm:
why might you want to increase friction?
how can you increase friction?
Brainstorm:
why might you want to decrease friction?
how can you decrease friction?
Units:
the Joule (J)
1J = 1N∆m
Spot the energy transformations
To work or not to work?
How can we calculate work when the force is not in the same direction as the displacement?

Does friction do work?
the force and displacement must be in the same direction for work to occur
Work-energy principle
We can express the transformation of energy from one form into another as energy transformation equations
Create an energy transformation equation for turning on a battery-powered flashlight
A.
Describe the motion of the particles in the different states of matter...
How many lightbulbs?
Test in Algodoo
What about if a ball is dropped vertically and from a pendulum from the same height? Which will be traveling the fastest at the bottom?
The cost of a kWh:
0 K = -273.15˚C
˚C = K + 273.15
Heating curves express the temperature of a substance as you add heat
Calculate how much heat you would have to add to 500mL (0.50 kg) of water to raise the temperature from -20˚C ice to 120˚C steam.
Putting it together...
latent heat is the heat released or absorbed when a substance changes state
specific latent heat of vaporization
- heat required to evaporate or condense 1kg of a substance
specific latent heat of fusion
- heat required to melt or freeze 1kg of a substance
Calculating Energy in Phase Changes
Calculating Energy for Heating Up/Cooling Down
c = specific heat capacity, how much energy it takes to raise the temperature of 1 kg of a substance by 1˚C
One thing that Einstein proved is that mass and energy are essentially equivalent.
Using this we can extend our Law of Conservation of Mass to the:
So what happens when we try to convert mass to energy?
Stellarator
Alpha Decay - emission of an alpha particle (Helium nucleus) during fission
Beta Decay - emission or absorption of a beta particle (electron or positron) when a proton turns into a neutron or a neutron into a proton
Gamma Decay - emission of a gamma ray (very high energy light) from an excited nucleus
This stuff is happening all the time around you!
The business of death...
http://nigelstanford.com/Cymatics/
If a tree falls in the forest and nobody is there to hear it does it still make a sound?
Vibration:
a cyclical motion about an equilibrium point
Harmonic motion:
motion that repeats itself periodically
Mechanical wave:
the transfer of energy through a medium due to a vibration
A. Types of Waves
B. Sound
List some examples
Which types of materials can transmit transverse and longitudinal waves?
What do we call the critical points of longitudinal and transverse waves?
Energy produced by vibrating objects detectable by the ear.
Is sound a mechanical wave?
Which type of wave is sound?
What is the medium (usually) with sound?
Cymatics
A. Characteristics of waves
amplitude
wavelength (lambda)
Physical Characteristics
period
frequency
Temporal (Time-based) Characteristics
phase shift
phase shift
How do each of these characteristics affect sound?
B. The speed of waves
Waves travel at different speeds in different media
What do you notice about the speed in solids, liquids and gases? Why is this?
Do you think that sound travels faster in warm air or slow air?


There are specialized equations to calculate the speed of waves in different types of objects, such as strings
The Universal Wave Equation
relates the speed of a wave to the frequency and wavelengh
derived from v=d/t
which units are to be used?
Loudness and distance
decibels, mach, sonic boom
http://phet.colorado.edu/en/simulation/legacy/wave-interference
Wave Interference Applet
4.4 Combining Waves
A. Wave Reflections
what happens when a wave meets a boundary?
what is the difference between a fixed and free end?
https://phet.colorado.edu/en/simulation/wave-on-a-string
Interactive Wave Simulation
B. Wave Interference
what happens when 2 waves meet?
C. 2D Wave interference
what happens when the waves from 2 sound sources interfere?
http://phet.colorado.edu/en/simulation/legacy/wave-interference
Wave Interference Simulation
A. In and out of Phase
http://www.acs.psu.edu/drussell/Demos/superposition/superposition.html
Constructive Interference
Destructive Interference
when two waves meet and produce a wave with a larger amplitude
when two waves meet and produce a wave with a smaller amplitude
Principle of Superposition
the amplitude of interfering waves is the sum of the amplitudes of the individual waves
What happens when you hear more than one wave at a time?
http://www.physicsclassroom.com/Physics-Interactives/Waves-and-Sound/Standing-Wave-Patterns/Standing-Wave-Patterns-Interactive
4.5 Standing Waves
Standing Wave Patterns Interactive
How do instruments create sounds?
How do waves interfere when they are in phase?
How do waves interfere when they are out of phase?
How do noise canceling headphones work?
B. Different Frequencies
How do waves interfere when they are different frequencies?
They form intervals.
Interval:
difference between 2 frequencies
How come some intervals sound nice and others do not?
C. Slightly Different Frequencies
http://www.acs.psu.edu/drussell/Demos/superposition/superposition.html
How do waves interfere when they have slightly different frequencies?
Beats can actually be used to tune instruments!
beat frequency = difference between frequency of 2 waves
A. Creating Standing Waves
B. Resonance
Why do different instruments sound different?
The character of a musical instrument's sound is called its
timbre
Resonant frequency:
the frequency an object will naturally vibrate at (ie. the pitch of a guitar string)
Resonance:
when an object forces another object to vibrate at a certain frequency (pushing a swing at the right time)
Damping:
when the vibration in an object is reduced (pushing a swing at the wrong time)

Tuning fork demo...
2 ends fixed
1 end fixed
both ends open
**identify the nodes and antinodes
Using echo location
4.6 Sound and Movement
A. The Doppler Effect
What do you hear when a car drives by?
http://www.animations.physics.unsw.edu.au/jw/doppler.htm#example
as a source of sound approaches an observer, the frequency of the sound increases
as the source of the sound moves away from the observer, the frequency of the sound decreases
The Doppler Effect
The Sonic Boom
When we're hearing all the instruments in an orchestra playing all at once, what are we actually hearing?
harmonica
clarinet
music box
ocarina
human voice
flute
wind chimes
piano
guitar
violin
Note: the pitch of an instrument is the loudest and lowest perceptable frequency created by an instrument, usually the fundamental
B. The Perception of Pitch
we perceive pitch logarithmically instead of linearly
each note (semitone) is 2^(1/12)x the previous pitch
test this out below: http://www.audiocheck.net/soundtests_nonlinear.php
why might this have been an evolutionary advantage?
How many volts?
What about batteries connected in series or parallel?
More voltage
Last longer
Superconductors
Non-Ohmic Resistors
https://phet.colorado.edu/en/simulation/legacy/circuit-construction-kit-ac
Circuit Builder
https://phet.colorado.edu/en/simulation/legacy/circuit-construction-kit-ac
Circuit Builder
Are current and voltage related?
B. Any Exceptions to Ohm's Law?
Is it possible for a material to have 0 electrical resistance?
When a light bulb or resistor heats up, the resistance tends to increase as well
https://en.wikipedia.org/wiki/Drift_velocity
A. Magnetic Fields
Lenz's Law
http://phet.colorado.edu/en/simulation/legacy/generator
Magnetic Field phet
opposite directions of fields
field lines represent the path a N monopole would act near the magnet
field lines go from north to south
field lines may not cross
lines closer together represent a stronger field
Drawing magnetic field lines
same directions of fields
B. Effects of moving charges on magnetic fields
C. Effects of magnetic fields on conductors
a current passing through a wire will create a magnetic field
use the right hand rule (RHR) to determine the direction of the field
According to the motor principle, what happens when you put two wires beside each other
with currents flowing in the same direction?
with currents flowing in opposite directions?
The Motor Principle
when a charge moves through a conductor in a magnetic field, there will be a force on the conductor
the direction of the force is according to the right hand rule
Solenoids
DC Motors
http://www.electricaleasy.com/2014/01/basic-working-of-dc-motor.html
How can we take advantage of the motor principle?
What will happen below:
Another application of the motor principle
Example problems:
Oersted's Principle
How can we take advantage of Oersted's Principle?
a coil of wire with a current passing through it is called a solenoid
solenoids act similarly to permanent bar magnets
Electromagnets
Speakers
Solenoid Lock
Faraday's Law of Electromagnetic Induction
a change in magnetic field induces a voltage (and current) in a conductor
use the RHR to determine the direction of the current
Which direction is the conventional flow?
What about the electron flow?
AC Generator
Electric Guitar Pickups
See phet demo
Look familiar?
If a changing magnetic field induces a current in a coil, the electric current produces a force that opposes the change
Two sides of the same coin...
Try it!
What is 10m/s in km/h?
Unit Conversion and
Dimensional Analysis
Dimensional analysis is a method for converting units using conversion factors
How many seconds in 2 years?
Behind the Scenes
note:
ignore
exact numbers
when considering the number of significant figures (they have an infinite number of decimal places)
study of matter and energy and the forces that describe the way the universe behaves
A. Mass and Weight
What do these measure?
C. Terminal Velocity
Draw a FBD for the following:
1. A parachutist when they jump out of a plane
2. A parachitist as they gain speed
3. A parachutist as the parachute is deployed
4. A parachutist standing on the ground



Terminal velocity
Speed in which the drag force is equal to the gravitational force.
Fastest free fall speed of object in a medium
Force-Displacement Graphs
Mr Notten pulls a 10kg block across the ground at a constant velocity using a force of 200N for 5m. He then lets go.
1) What will happen to the block?
2) Draw a Force-Displacement Graph.
1) Describe what is happening.
2) How much work is done to the object?
Amp-Hours
amp-hours = amps provided x hours in operation
Amp-hours (A-h) are used to determine how long a battery will last.
It is a measure of total charge a battery is able to move through a circuit
Drawing fields into and out of the page:
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