1
About Science
What is Physics?
Four Forces
Scientific Method
Linear Motion
Speed and Velocity
Lab: Finding Distance and Average Speed
Acceleration
Lab: Finding Acceleration and
Final Velocity
Freefall
Class Activity: Measuring Reaction
Time
Class Activity: How Fast and High can
you throw a ball?
Chapter 2 Review
Projectile Motion
Vectors and Components
Projectile Motion
Lab: Determining Projectile Velocity
Upwardly Launched Projectiles
Chapter 3 Review
2
Unit II – Laws of Motion
Newton’s 1st Law of Motion
Mass, Weight, and Volume
Inertia
Equilibrium and Net-Force
Newton’s 2nd Law of Motion
Newton’s Second Law
Lab: Newton’s 2nd Law
Friction and Air Resistance
Pressure
Class Activity: Weighing a Car
Newton’s 3rd Law of Motion
Newton’s 3rd Law
Unit II Review
Momentum
Momentum and Impulse
Bouncing and Collisions
Law of Conservation of Momentum
Chapter 7 Review
3
Electrostatics
Electrical Forces and Charges
Methods of Charging
Coulomb’s Law
Electric Current
Flow of Charge
Ohm’s Law
Source of Electrons
Electric Power
Class Activity: Electric Cooking with
Julia Childs
Electric Circuits
Series Circuits
Exploratory Activity: Series Circuits
Parallel Circuits
Exploratory Activity: Parallel Circuits
Compound Circuits
Electricity Unit Review
Magnetism
Magnetic Fields
Electromagnetism
Transformers
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Chapter 1 Highlights:
The Four Natural Forces
Scientific Method
Key Terms
Force
Motion
Scientific Method
Laws
Hypothesis
Matter
Energy
Facts
Principles
Theory
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What is Physics? The study of matter and energy, the motion of matter, and
forces on matter
 Involves the study of four things and their interactions
1. Matter – all objects are composed of massive particles
2. Energy – the release of energy produces force on matter or to another
form of energy
3. Forces – change the state of motion or energy
4. Motion – Newton’s laws of motion that governs all material objects
The Four Natural Forces
1. Gravity – force between matter (planets, falling objects)
2. Electromagnetic – force between charges (electricity, lightning)
3. Weak Nuclear – force that governs radioactive decay (radiation sources)
4. Strong Nuclear – force that holds the nucleus together (nuclear power)
Why is physics the basic science? Physics is fundamental to all the other
sciences. Physics explains the properties and processes of Chemistry and
Biology.
What is the language of physics? Why? (4 main reasons) Math. It: predicts,
provides proof, universal, logical
Scientific Method
1. Identify the Problem
2. Form a hypothesis
3. Perform experiments
4. Make Observations
5. Form Conclusion
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Facts – known pieces of information that are true for scientists
Laws/Principles – organized group of facts that have been tested and are shown
true over experimentation.
Hypothesis – educated guess on organizing data or before observations are made
 Must be testable!
Theory – a hypothesis with some supporting evidence
 By definition – can’t be proved
Is the scientific method followed strictly? Explain. No. sometimes a step is
skipped due to the nature of the problem. New information is found through
experimentation and the hypothesis is changed. Conclusions can be false and
the process starts over.
 Underlying all scientific theory/models are assumptions
What are assumptions? Are things that make models easier to use.
Example – atomic theory; protons, neutrons, electrons are not small spheres?
They don’t “orbit” the way they are pictured (modeled).
When are theories, models, hypotheses changed? When there is conclusive
contradictory evidence.
Assignment Ch. 1: RQ 1-5
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Chapter 4 Highlights:
Vector and Scalar Quantities
Adding Vectors
Average Speed vs. Instantaneous Speed
Speed vs. Velocity
How Velocity Changes
Constant Speed and Distance
Constant Acceleration and Distance
Freefall Acceleration
Key Terms
Speed
Average Speed
Vector
Acceleration
Freefall
Instantaneous Speed
Velocity
Scalar
Gravity
Acceleration due to Gravity
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Review of how we measure things in science:
SI Units (Systeme’Internationale) – International standard for the
measurement of scientific data
SI Unit
English (American) Unit
Length
Meter (m)
Foot (ft)
Time
Second (s)
Second (s)
Weight
Newton (N)
Pound (lb)
Mass
Kilogram (kg)
Slug (sl)
Velocity
m/s
ft/s
Acceleration
m/s2
ft/s2
How fast can you run? How fast is telling us your speed.
Student example running down and back in the hallway. Collect data, calculate
average speed. Discuss results.
Speed =
Speed gun measurement =
What do you need in order to determine this?
1. A measurement of distance
2. A measurement of time to cover the distance.
3. A reference point = usually a stationary point.
Speed – (units =
m/s
time.
Speed = dist./time
) is a rate at which distance is covered per unit
SI Units =
m/s
American Units =
ft/s
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The speed or motion of an object is
relative to other measuring points.
What is meant by this statement? With respect to a common measuring point.
What do we commonly take measurement relative too? Why? The surface of the
earth. It is common to everyone.
If a car traveled an average 25 mph for 2 hours, what distance did it travel?
Discuss. 25 mph x 2 hours = 50 miles?
 Without a reference point the car could’ve traveled 0 miles to 50 miles.
Instantaneous Speed – (speedometer of a car) how fast an object is traveling
at a moment in time.
Average Speed – total distance traveled in a period of time. It ignores
changes in direction.
Velocity – speed with direction. – net-distance traveled from a reference
point (displacement) per unit time.
 Need direction – velocity is a vector
Scalar – just a descriptive number – 25 kg, 30 N, 98.6 oF
Vector –a scalar with a direction – 50 m/s due north, 30 N to the right
1. The speedometer in every car also has an odometer that records the
distance traveled.
a. If the odometer reads zero at the beginning of a trip and 35 km a
half hour later, what is the average speed?
Speed = 35 km / ½ h = 70 km/h
b. Would it be possible to attain this average speed and never exceed
the average speed from a? No. By definition of average there must
be a point where you’re traveling faster than your average.
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2. If a cheetah can maintain a constant speed of 25 m/s, it will cover 25
meters every second. At this rate, how far will it travel in 10 seconds?
In one minute?
S = d /t ; d = s t
D= 25 m/s (10s) = 250 m ; 25 m/s (60 s) = 1500 m
3. The speedometer of a car
another car that travels
same speed? Do they have
Yes. No, they are traveling in
moving northward reads 60 km/h. It passes
southward at 60 km/h. Do both cars have the
the same velocity?
different directions!
Assignment Ch. 4: 1-5, 26-31
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Name(s):
Period:
_________________
_________________
_________________
Purpose:
To find the average speed of a student by measuring distance and time. The
student will then use one of the calculated average speeds to predict an
unknown distance. The student may use any materials as necessary.
Procedure:
The student will measure five (5) different ways the student can travel the
distance (i.e., run, walk, hop, skip, leap, crawl, cart wheel, etc.). For
each race, try to keep your speed as constant as possible throughout the
distance traveled!
Be sure to SHOW ALL YOUR WORK!
Activity
Time (sec.)
Distance (m)
Ave. Speed (m/s)
1
2
3
4
5
Calculate your average speed in the space below:
Use ONE of your activities from above to calculate an unknown distance:
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1. Did your average speed indicate your instantaneous speed? Explain.
2. Were there instances, in the same activity, where you were traveling
faster than your average speed?
3. Were you traveling at a constant speed throughout the whole distance?
What was happening to your speed throughout the distance you traveled?
4. What were some of the things you ignored during your timed trials?
5. Convert each of your average speeds into miles per hour just for
comparison. (1 m/s = 2.24 mph)
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If you are stopped at an intersection and you want to travel the next 50
miles in 1 hour. What average speed must you have?
50 miles per hour.
Was there a point at which you were traveling faster than this average?
Yes. It is an average.
What was your absolute lowest speed? What could be your max. speed? Discuss.
Could be 0 mph. Top speed of your car.
During your car ride you had to get from one point to the next. Your velocity
changed throughout the trip. How do you know your velocity changed, and what
did the car do in order to change it?
You felt your body being pushed, pulled in different directions – accelerate.
Demo: student on rolling chair
1. Step on gas – accelerate – pick up speed
2. Step on brake – decelerate – lose speed
3. Turn – changes direction
Acceleration – (units = _m/s2______) the rate of change in velocity per unit
time. * Velocity is a vector which has direction! Change in is final velocity
minus initial velocity.
a = __V______
a = Velocity
t
time
 Rearrange this equation gives us the instantaneous velocity when
undergoing a constant acceleration:
V = a t
If a car accelerates constantly from rest to 60 mph (27 m/s) in 6 seconds:
a. What is the cars acceleration?
A = (27m/s – 0 m/s) / 6 s = 4 ½ m/s2
b. What is the cars average speed?
S = (27 + 0) /2 = 13 ½ m/s
c. What distance did the car travel in this time period?
D = s t = 13 ½ m/s (6 s) = 81 m
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Fill in the following table of an object accelerating at 5 m/s2 with the time
values given:
Time (s)
Instantaneous Velocity (m/s)
Distance Traveled (m)
0
0
0
1
5 m/s
2 ½
2
10 m/s
10
3
15
22.5 m
4
20
40 m
5
25
62 ½
Calculations:
Under constant acceleration, as the time increases the velocity increases the
same amount each second. What happens to the distance covered each second
under constant acceleration? It increases also. Every second the speed
increases; the distance covered each 1 second time interval also gets larger.
Equation that describes the distance covered from rest while constantly
accelerating:
d = ½ a t2
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1. Suppose a car moving in a straight line steadily increases its speed
each second, first from 35 to 40 km/h, then from 40 to 45 km/h, then
from 45 to 50 km/h. What is its acceleration?
5 km/h/s
2. In 5 seconds a car moving in a straight line increases its speed from
50 km/h to 55 km/h, while a truck goes from rest to 15 km/h. Which
undergoes greater acceleration? What is the acceleration of each
vehicle?
Truck. 1 km/h/s, 3 km/h/s
3. During the span of 1 second, an object starts at 10 m/s and ends at 20
m/s. What is the average speed of the object during this time interval?
What is its acceleration?
S = (20 + 10)/ 2 = 15 m/s
A = (20 – 10)/ 1 s = 10 m/s2
Assignment Ch. 4: 6-9, 32-36
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Name(s):
_________________
_________________
_________________
Period:
Purpose:
To calculate the acceleration and final velocity of a match-box car rolled
down a ramp at increasing angles.
Procedure:
Measure the distance the matchbox car will travel down the ramp and measure
the time taken to cover that distance. Note how the velocity of the matchbox
changes as it rolls down the ramp. Also note how the accelerations of the
matchbox car are different for increasing angles.
Angle (Deg.)
Acceleration (m/s2)
Velocity (m/s)
10
30
50
70
90
Calculate your acceleration using your distance equation:
Calculate your final velocity using your velocity equation:
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1. How do you know your matchbox car accelerated?
2. What happened to the value of the matchbox cars acceleration as the ramp
angle was increased?
3. What happened to the matchbox cars final velocity as the ramp angle was
increased?
4. What were some of the things that were difficult to measure in this lab?
5. What happened when the matchbox car was on the incline at 90o?
6. What do you think would be the maximum acceleration of a matchbox car in
this kind of experiment? When does this occur?
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When a skydiver jumps out of an airplane at 14,000 ft, she is said to be in
freefall. What is freefall? What happens when freefall occurs?
Gravity is pulling the skydiver down. The skydiver accelerates downward
toward the earth.
Video:
Demos:
Skydiving
book vs. paper
paper ball vs. book
penny and paper in a vacuum
In freefall, what quantity do we ignore, or limit?
Air resistance. It slows things down.
How does a freely falling object drop?
Downward – toward the center of the earth.
Does it pick up speed as it falls from rest? How do we know? Does it have a
value or number?
Yes. It started from rest and now it is traveling at a certain speed. Yes, it
is considered constant when near the surface of the earth.
How can we figure it out? Discuss.
Yes. Use a motion equation.
Freefall – an object accelerating downward by gravity without air resistance.
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Name(s):
Period:
_________________
_________________
_________________
Purpose:
Calculate the acceleration due to gravity by dropping a softball from a large
known height and measuring the time taken to fall that distance.
Distance = 5.7 m
Measure the time with a stop watch:
Use your distance equation to calculate the value of the acceleration.
SHOW ALL OF YOUR WORK!
Time (s)
Average time = _________
Calculated acceleration = ________________
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 The accepted value for the acceleration due to gravity: g = 9.806 m/s2
For practical purposes: g = 10 m/s2
 That means for every second of fall, or for every second an object is
falling, the object will gain __10___ m/s downward.
𝒗 = 𝒈𝒕 = 𝟏𝟎𝒕
𝟏
𝒅 = 𝒈𝒕𝟐 = 𝟓𝒕𝟐
𝟐
What happens when a ball is thrown upward?
It travels upward, then stops instantaneously, and comes back down.
What happens to the balls velocity as it travels upward? Why does it do this?
It slows down until it reaches the top. The acceleration due to gravity is
opposite to the velocity of the ball.
What is the rate of this change?
It slows down at 10 m/s every second until it reaches the very top.
What happens to the balls velocity on the way down?
It speeds up on the way down.
What is the rate of this change?
The rate is that of gravity = 10 m/s every second.
1. What would be the speedometer reading on a falling rock after 1 second
of fall? 2 seconds? 4 seconds? 8 seconds?
V = g t ; v = 10 (1 s) = 10 m/s,
20 m/s, 40 m/s, 80 m/s
2. What would be the odometer reading on a falling rock after 1 second of
fall? 2 seconds? 4 seconds? 8 seconds?
D = ½ g t2 = ½ 10 t2 = 5 t2 = 5 (1)2 = 5 m,
20 m, 80 m, 320 m
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3. A ball is thrown upward with a speed of 30 m/s. Calculate the speed of
the ball 1 second after the throw. 2 seconds. 3 seconds. 4 seconds. 5
seconds. 6 seconds.
20 m/s, 10 m/s, 0 m/s, -10 m/s, -20 m/s, -30 m/s
a. What do you see happening to the velocity of the ball?
Slowing down at 10 m/s on the way up, then speeding up downward.
b. Explain what happens to the ball after 3 seconds.
The ball is instantaneously stopped at the very top – it is the turn-around
point.
c. Explain what is happening to the ball at 6 seconds.
At the 6 second mark it is at the same level that it was thrown and traveling
with the same speed but opposite direction.
Assignment Ch. 4: 10-15, 18, 19, 37-41
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Can you grab this package of M&Ms before it strikes the ground given these
initial conditions? No. the time it takes for you to clasp your fingers is
more than the time required for gravity to accelerate it from between your
fingers.
Name(s):
Period:
_________________
_________________
_________________
Purpose:
Measure your reaction time by using the distance equation.
Procedure:
Have your lab partner drop a meter stick or ruler between your index finger
and thumb. Start with your fingers on either side of the 0 point on the
ruler. The lab partner then drops the ruler and you grab it as fast as you
can. The time it takes gravity to pull the ruler down a distance equal to the
where your fingers grab the ruler is your reaction time.
Use your distance equation to calculate the value of the reaction time. SHOW
ALL OF YOUR WORK AND REMEMBER TO CONVERT YOUR MEASUREMENTS!
Distance (m)
Time (s)
Average time =
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Name(s):
Period:
_________________
_________________
_________________
Purpose:
Calculate how fast a person can throw a ball into the air using the velocity
equation. Calculate how high the throw was using the distance equation.
Procedure:
Throw a ball into the air as hard as you can making it go as straight up as
possible. This is not an ideal throwing position but will make the
calculations easier. When calculating the velocity of the throw you have to
use the properties of freefall. One property is that the ball stops at the
top of the throw – at its maximum height. Another property is that the ball
will be traveling just as fast when it strikes the ground as it was when it
was thrown. Lastly, the time taken for the ball to go from the top to the
ground is ½ of the total time the ball spent in the air. We are going to
assume that the initial height of the throw is negligible.
Measure the time of the throw with a stop watch, from the point the ball
leaves the hand to when the ball hits the ground. Divide the time by 2 to
find the time it takes the ball to reach the ground from the highest point.
Use your distance equation to calculate the value
of the acceleration. SHOW ALL OF YOUR WORK!
Time (s)
Average time = _________
Calculated v = ___________ m/s
Calculated height = ____________ m
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 Write down key terms with their definitions.
 Write down the equations used in the Chapter.
 Solve the following example questions:
1. What is motion relative to?
2. Speed is the rate at which what happens?
3. Explain the difference between instantaneous speed and average speed.
4. Explain the difference between speed and velocity.
5. Calculate the average speed of a human running 18m in 3s.
6. Calculate the distance traveled by the person from #5 in 30 min.
7. Calculate the acceleration of a matchbox car that rolls down a 3m ramp
in 1.5s.
8. Calculate the speed and the distance fallen by a ball that is dropped
from rest in the time intervals of 1second through 7 seconds.
9. Calculate the height of a ball thrown upward at 12 m/s.
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Chapter 5 Highlights:
Vector Components
Relative Velocities at Angles
Projectile Components
Horizontal Projectile Motion
Projectile Range
Calculating Projectile Velocity
Upwardly Launched Projectiles
Key Terms
Vector
Components
Range
Pythagorean Theorem
Resultant
Projectile
Time of Flight
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If you could run at a speed of 10 km/h for 2 hours, how far could you run
from home?
20 km?
Does running at this rate for this long tell you how far you ran from home?
No, without a reference point you don’t know.
What would be the different possibilities for the distances traveled?
Anywhere from 0 up to 20 km.
1. How far did you drive if you drove at 20 km/h for 1 hour north, and then
drove an additional 50 km/h for 2 hours north?
20 km + 100 Km = 120 km
2. How did you add these together?
One right after the other – they were in the same direction.
3. How far did you drive if you drove at 30 km/h north for 2 hours and then
drove at 40 km/h south for 2 hours?
60 km – 80 km = -20 km, the directions were opposite so you subtract the
quantities.
4. How far did you drive if you drove at 40 km/h north for 2 hours and then
drove at 40 km/h east for 2 hours?
80 km + 80 km = ?
802 + 802 = d2,
d = 113 km northeast
5. How do you add these together? you have to use pythagorean’s theorem to
figure it out because the directions are perpendicular to each other!
Vector – a magnitude (scalar quantity) with a direction
Resultant – a vector that is the combination of 2 or more vectors
 Vectors are represented as arrows. The length of the arrow indicates its
magnitude (scalar), and the tip shows its direction.
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1.
2.
7 m south + 3 m north
4 m north + 8 m north
4 m south
3.
12 m north
4.
7 m east + 8 m west
3 m north + 4 m east
1 m west
5 m northeast
Pythagorean Theorem – a math method used to add perpendicular vectors
a2 +b2 = c2
Components – two perpendicular vectors that represent a single vector
 Usually an x-comp. and a y-comp.
1.
2.
24 m
10 m
26 m
8 m
6 m
10 m
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Graphically Draw the Component Vectors for each Resultant:
How fast is the airplane going relative to the ground? The Plane flies at 100
km/h due north and the wind blows at 25 km/h whose direction is indicated by
the arrow.
W
W
125 km/h north
W
75 km/h north
103 km/h northeast
Assignment Ch. 5:1-5,18-21, 37, 38
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What is a projectile?
An object traveling through the air influenced only by gravity.
What governs a projectile?
Gravity, initial velocity, launch angle
What kind of a path does a projectile form? parabola
Which of these objects would be considered a projectile? Why?
Football, ball, Frisbee, airplane, balloon
Only the football and ball because the others have another force acting on
them.
Would a rocket be considered a projectile? Why?
No. it has another force acting on it.
Which of these two objects will hit the ground first when dropped from the
same height at the same time? Same time – property of gravity.
Demo: steel ball bearing, plastic ball
Why does this happen?
All objects fall at the same rate without air resistance.
What would happen to the time spent in the air if these two objects were
dropped from the same height at the same time, but one of them were initially
moving horizontally? Nothing. Both fall the same vertical distance in the same
amount of time.
Demo;
Ball launcher and drop
Race cars off track
What direction and only direction does gravity act?
Downward.
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x-direction – (horizontal) – the horizontal velocity doesn’t change.
 Range – distance covered across the ground by a projectile.
y-direction – (vertical) – the vertical velocity is always changing due to
gravity.
Which component determines the time of flight? Y - direction
x-component equation: X = vx t
y-component equation: g = 10 m/s2
y = ½ g t2 = 5 t2
vy = gt = 10 t
vi = 30 m/s
Each second of fall this ball is projected
horizontally 30 m.
Examples:
1) Using Dia. 1 as a guide, answer the following questions. Each successive
ball represents a 1 second time interval.
How long was the ball in the air?
5s
What is the range of the ball?
X = 30 (5) = 150 m
How far down did the ball fall?
Y = 5 t2 = 5 (5)2 = 125 m
What is the final velocity for each ball? V = 50 m/s; v2 = 502 + 302, v = 58.3 m/s
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Objective: To calculate the velocity of a projectile that is fired
horizontally using the projectile motion equations.
Theory/Procedure: The range of the projectile is given by the equation,
X = vxt
Where t is the time of flight, and vx is the horizontal velocity of the
projectile. The time of flight is calculated from the main y-equation
H = ½ gt2, where g = 10 m/s2.
Height
Range
Write down which launcher you are using _____________.
Measuring the range of the
Launch
projectile
To calculate the velocity of the projectile,
1
you must first measure the average range of
2
the projectile. Launch the projectile 10
times onto the floor and measure the range
3
of each launch starting from the end of the
4
launcher to where the projectile hits the
floor. Average the measured values.
5
Calculating the time of flight
Measure the distance from the bottom of the
launcher’s muzzle to the floor.
H = ___________ m
Use your height equation from above to
calculate the time in the air.
Calculated time, t = ___________
Range (m)
6
7
8
9
10
Average
Range =
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Calculating the Initial Velocity of the Projectile
Use the range equation, the calculated time of flight, and your average range
to find the horizontal velocity (vx) of the projectile.
vx = ____________ m/s
Questions:
1. What would happen to the range of the projectile in this lab if the
velocity of the launcher was increased?
2. What would happen to the time of the projectile in this lab if the
velocity of the launcher was increased?
3. What would happen to the range of the projectile in this lab if the
height of the lab table was increased?
4. Calculate the range of your projectile if the speed of your projectile
launcher is 20 m/s and the height of your lab table is 1.1 m.
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What happens to the range of a projectile when launched at increasing angles
from the horizontal? The range increases to 45o then decreases to 90o
Demo:
hose and water
Tennis ball launcher
Launcher at angles
What pairs of angles give the same range? Why? Angles that add together
- at a small angle ___30____
to be 90o
Vy component is __small___
time of flight is _small___
but the Vx component is __large__
- at a large angle __60__
Vy component is _large__
time of flight is _large__
but the Vx component is _small_
What are these angles called? Complimentary angles
What is the angle that gives a maximum range? Why?
45o, Gives the largest amount of time in the air for the largest horizontal
speed.
Shooting the Monkey
Where should a hunter aim to tranquilize the monkey hanging in the tree?
A. Right above the monkey
B. In the middle of the monkey
C. Right below the monkey
Why does this work?
Both objects will fall the same vertical distance from a straight line path in
the same amount of time.
Questions:
1. A projectile is shot at an angle into the air. Neglecting air
resistance, what is its vertical acceleration? Its horizontal
acceleration? 10 m/s2, 0 m/s2
2. At what point in its path does a projectile have minimum speed?
At the highest point – it’s all horizontal speed.
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10
m/s
10
m/s
10
m/s
20
m/s
14
m/s
10
m/s
30 m/s
22.4
m/s
10 m/s
31.6
m/s
A toy cannon is shot almost straight up into the air. The velocity components
of the cannon ball are given in the diagram above. If the acceleration of the
cannon ball is g = 10 m/s2. Each successive ball on the parabolic path
indicates a 1 second time interval.
What are the missing velocity values indicated by the empty boxes?
What is the range of the toy cannon ball? X = 10 m/s (6s) = 60 m
Assignment Ch. 5:
10a, 11-13, 27, 30, 34, 40, 42-44
35
 Write down key terms with their definitions.
 Write down the equations used in the Chapter.
 Solve the following example questions:
1. How does a vector quantity differ from a scalar quantity?
2. Calculate the resultant of two vectors with a magnitude of 3 km and 4km
that are at right angles to each other.
3. Calculate the resultant velocity of an airplane that flies at 100 km/h
through the air and encounters a 75 km/h head wind. A 75 km/h tail wind.
A 75 km/h cross wind that acts at a right angle to the airplane.
4. In the absence of air resistance, why does the horizontal component of
velocity for a projectile remain constant while the vertical component
changes?
5. What is freefall acceleration?
6. At the instant a ball is thrown horizontally an identical ball is
dropped from the same height. Which of the two balls will hit the ground
first? Why?
7. How far below an initial straight-line path will a projectile fall in 1
second? 2 seconds? 3 seconds?
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8. Neglecting air resistance if you throw a ball into the air with a speed
of 20 m/s how fast will it be traveling if it is caught at the same
height on its way back down?
9. Does #8 depend on the angle with which the ball is thrown?
10.
At what angle will a cannon ball fired from a cannon achieve
maximum height? Maximum range?
11.
What angles will give a projectile the same range?
12.
Calculate the range of a projectile that is fired with an initial
horizontal speed of 20 m/s from a building 45 m high.
13.
A toy car traveling horizontally across a table top 1m high falls
to the floor. The toy car travels a distance of 2 m across the floor.
How fast was the toy car traveling when it left the table top?
37
Chapter 3 Highlights:
Mass vs. Weight vs. Volume
Inertia
Force and motion
Net-Force and Equilibrium
Key Terms
Inertia
Net-Force
Vectors
Mass
Support Force
Tension Force
Normal Force
Weight
Volume
Pythagorean Theorem
Equilibrium
Friction
Newton
38
What is mass? Mass is the amount of “matter” in an object?
Demo: shotput vs. ball
Mass – the amount of matter in an object
Weight – the force of gravity on an object
Volume – the amount of space an object occupies
Activity: Finding your mass
1 kg = __2.2_____ lb. = ___10_____ N
1. Does a 2 kg iron block have twice as much mass as a 1 kg block of
iron? Twice as much volume? Twice as much weight, when
measured at the same location? Yes, Yes, Yes.
2. Does a 2 kg bunch of bananas have twice as much mass as a 1 kg
block of iron? Twice as much volume? Twice as much weight,
when measured at the same location? Yes, No, Yes.
3. A 1 kg bag of nails weighs 10 N at the surface of the earth. What
does a 2 kg tub of butter weigh? 20 N
Assignment Ch. 3: 12-18, 23-27, 37, 39-40, 51-55
39
What will happen if a foam ball is thrown toward a student?
Nothing, the ball will simply bounce off.
What will happen if a shot put is thrown toward a student?
The student would be seriously injured if done.
Why is the second situation more dangerous?
When moving, the larger mass is harder to stop moving.
Inertia – an object’s resistance to change to motion – it is the
measure of mass.
Demos: cup and coins, paper and cups, matchbox cars on ramps, bottle
and silk sheet, coins on elbow, chalk in a bottle, film cases and paper
strip, student on moving cart catching ball.
What is common in all of these cases?
They all had mass that did not change its state of motion.
What happened when the matchbox car rolled down the ramp? Did it
reach approx. the same height on the other side? Explain.
It rolled up the other side. Pretty close. The force of gravity caused
it to slow down when rolling up the side.
What happened when the track turned into a flat level track? Why did
it do this? Since there’s no force to slow it down, the car kept
traveling down the track.
If friction can be ignored, what force is necessary to keep an object
moving? None.
Newton’s 1st Law of Motion – an object at rest stays at rest, an object
in motion stays in motion until acted upon by an outside net-force.
 Called the law of inertia
 More mass = __more inertia___ = __more resistance_
 Must have an external net-force to change motion
o External force – a force acting on a separate mass.
Net– Force – the sum of all the forces acting on an object.
40
1. A ball is rolled across a counter top and rolls slowly to a stop.
How would Aristotle interpret this behavior? How would
Galileo?
A constant force is needed to keep an object moving. Friction
slowed the ball down.
2. If the force of gravity between the sun and the planets suddenly
disappeared, what type of path would the planets follow?
A straight line path at a constant speed.
3. Is it correct to say that the reason an object resists change and
persists in its state of motion is that it has inertia?
Yes.
4. Fill in the table:
Object
Mass
Weight
Tub of Butter
1 kg
10 N
Apple
0.1 kg
1N
Text book
1.7 kg
17 N
Brass weight
10 kg
100 N
Large bag of Flour
5 kg
50 N
Assignment Ch. 3: 5-8, 28-36, 38
41
Weight of student and platform together = ____________ lb.
What would be the scale readings on opposite ends of the platform?
The total = the total weight
What do both scale readings measure? The total weight
Reposition the student on the platform, what is happening with the
scale readings? One goes up, the other goes down
What happens to the total of the two scale readings?
The sum stays a constant = total weight
Can there be more than one force acting on an object?
Yes. We all have multiple forces acting at the same time.
What happens when the forces are balanced?
The forces add to be 0.
Support Force – the force supplied against weight
Normal Force – usually a support force, this force acts perpendicular
to a surface in contact with an object
Equilibrium – when two or more forces acting on an object add to be
zero.
42
1. Calculate the net-force acting on the following objects:
4N
3N
4N
4N
3N
7 N right
1 N right
3N
5N
2. Calculate the missing tensions in the following diagrams that
produce equilibrium:
6N
?
? 4N
3N
9N
3N
5N
3. When you step on a bathroom scale, the downward force supplied
by your feet and the upward force supplied by the floor
compress a calibrated spring in the scale. The compression of
the spring gives your weight. In effect, the scale measures the
floor’s support force. What will each scale read if you stand on
two scales with your weight divided equally between them? What
happens if you stand with more of your weight on one foot than
the other? ½ your weight, one is more than the other, but both
will add together to be your total weight.
43
4. What happens to the tension in the strings as you increase the
angle between the two equally supporting strings? Tension
increases dramatically
5. A block has a weight of 1000 N on a weightless platform
suspended by two ropes at either end. The tension is given in
one of the ropes. Calculate the tension in the other rope based
on the diagrams below:
500 N
? 500 N
750 N
? 250 N
150 N
1000 N
? 850 N
? 0N
Assignment Ch. 2: 1-3, 9, 14, 15, 33-35, 42-46
44
Chapter 6 Highlights:
Force and Acceleration
Newton’s 2nd Law
Friction
Air Resistance and Terminal Velocity
Pressure
Key Terms
Force
Mass
Friction
Pressure
Acceleration
Inertia
Terminal Velocity
Pascal
45
Video clip: dodge neon vs. viper
Which of these cars will win this drag race? Why?
Dodge neon due to its smaller mass.
What causes changes in speed? An unbalanced force.
How do you know if you are being accelerated? You can feel the effects of
your inertia – your body will change its position.
 Mass – (Newton’s def.) – inertia, an object’s resistance to changes in
motion.
1st part – acceleration is inversely proportional to an object’s mass – an
increase in mass decreases acceleration.
Demo: students on cart w/ changing mass
2nd part – acceleration is directly proportional to the applied net-force –
an increase in force will increase acceleration.
Demo: students on cart w/ changing force
Newton’s 2nd Law of Motion – the acceleration of an object is = the net-force
divided by the object’s mass.
a = Fnet /m
Find the mass of a student.
1. Find the force of friction ___________ N
2. Calculate the student’s acceleration. Measure distance and time when
pulling with 40 N of force.
3. Calculate the student’s mass.
46
1. If a car can accelerate at 2 m/s2, what acceleration can it attain if it
is towing another car of equal mass? 1 m/s2
2. What kind of motion does a constant force produce on an object?
Constant acceleration.
3. Fill in the missing values in the table:
Force
Mass
Acceleration
100 N
2 kg
50 m/s2
50 N
5 kg
10 m/s2
200 N
10 kg
20 m/s2
250 N
50 kg
5 m/s2
480 N
120 kg
4 m/s2
Do Lab: Proving Newton’s 2nd Law
Assignment Ch. 6:
1-7, 22*,25-28,56 *calculate the forces and acceleration
47
Prove Newton’s 2nd Law by parts.
Newton’s 2nd Law consists of 2 parts.
Part 1) The acceleration of an object is inversely proportional to the mass
of the object.
a  1/ m
The first part predicts that an increase in mass, for a constant applied
force, will result in a decrease in acceleration.
Part 2) The acceleration of an object of constant mass is directly
proportional to the force applied to that object.
a  F
The second part predicts that an increase in force, for a constant mass, will
result in an increase in acceleration.
Combining the two parts together results in Newton’s 2nd Law equation:
F
a
m
The equation used to calculate the cart’s acceleration comes from equation:
d
1 2
at
2
distance = d = _________
150 g mass
Fg
48
Friction needs to be overcome in this lab before measuring any
quantities. Friction can be compensated by adding a little bit of extra mass
to the end of the pulley. The amount of mass should be enough to keep the
cart moving at a constant velocity across the tabletop. If you see the cart
increase in speed then too much mass was added to the end of the string. Add
this mass to the hangar at the end of the string.
Mass and Acceleration
The constant force used to
the pull of gravity on the
mass should be 150 g (0.15
accelerate the cart within
to overcome the friction.
accelerate the lab cart will be provided through
masses at the end of the string. The amount of
kg) and constant so that it will be enough to
reason. This mass is in addition to the mass used
Mass is the variable in this part so that is what will be manipulated to see
what will happen to the time to cover a measured distance. The mass will be
increased by stacking 500g (0.5 kg) masses on top of the cart each interval.
Record the total mass of the system in the chart below for each of the
trials. Measure the distance covered, and record the time the cart took to
cover that distance. Be sure to stop your timing when the masses hit the
floor and NOT when the cart reaches the end of the table. Practice timing the
cart first until you have a consistent time and record the value. The cart
should NEVER hit the pulley – this causes damage to the cart and pulley.
49
Trial
Total mass
Time 1
Time 2
Time 3
Ave.
Time
Acceleration
1
2
3
4
5
6
7
Analysis:
Show your calculations and fill in the table above:
After completing the table, plot the data points “Mass vs. Acceleration” on
the computer and find the best fit graph for your data. Attach each of the
plotted graphs to your lab.
50
1. What kind of graph do you get from “Mass vs. Acceleration”? Does this
graph reflect your theory? Explain.
2. Is your graph a straight line or a curve?
3. Based on the curve fit of your graph, could your acceleration ever be 0?
4. Does the acceleration of your cart increase or decrease with an increase
in mass? Explain why.
Force and Acceleration
Place 2 kg on your lab cart along with the set of 6 – 20g brass hangar
masses. This will be the constant mass of your system. Record the total mass
of the cart and masses.
Mass = ___2880__________ g
The pulling force will be the variable in this part of the lab. The force is
increased each interval by taking one of the 20 g brass masses off of the
cart and placing it on the hangar at the end of the string. Be sure to
convert the grams into Newtons. 1 g = 0.01 N
The acceleration will be calculated using your distance equation and your
average time just as in part 1 of the lab. Be sure to stop your timing and
the cart when the masses hit the floor!
51
Trial
Force
Time 1
Time 2
Time 3
Ave.
Time
Acceleration
1
2
3
4
5
6
7
Analysis:
Show your calculations and fill in the table above:
After completing the table, plot the data points “Force vs. Acceleration”on
the computer and find the best fit graph for your data. Attach each of the
plotted graphs to your lab.
52
5. What kind of graph do you get from “Force vs. Acceleration”? Does this
graph reflect your theory? Explain.
6. Is your graph a straight line or a curve?
7. Based on the fit of your graph, what is the slope of the graph? Compare
it to the total mass of part 2. What do you find?
8. Does the acceleration of your cart increase or decrease with an increase
in force? Explain why.
53
What happens when this desk is slid across the floor?
It will eventually stop.
Why does it stop?
A frictional force between the desk and the floor.
Friction – (Ffr) a contact force between surfaces that opposes sliding
motions.
 Does not depend on the contact area
 It is only determined by two factors
What do we use friction for? Can we live without it? Discuss.
Walking, sitting, stopping, etc. No, we need friction to do many things.
What creates friction?
Friction is created by the interlocking of microscopic fissures in the
surfaces.
What happens to the amount of friction when a sheet of paper is held loosely
vs. tightly? Tighter creates more friction – the fissures interlock harder.
What happens to the amount of friction when a sheet of paper is held with
wood blocks vs. rubber stoppers? The rubber has flexible fissures that will
fit into the fissures of the other easily.
What determines the amount of friction?
1. The normal force between the surfaces.
2. The types of materials in contact.
What can we do to reduce friction? (3 basic ways)
Lubrication – fills the fissures so they can’t interlock, make the surfaces
as smooth as possible – reduces the size of the fissures, use wheels – makes
sliding motion into a rotational motion.
Is there another kind of friction other than friction from surfaces?
Yes. Air friction, or fluid friction.
54
What happens when a sky diver pulls the rip-cord?
Air resistance increases.
Why does it do this?
Air resistance increases with the cross-sectional area of an object.
Air resistance – a frictional force caused by the movement of an object
through a fluid (air)
 Also called ___drag___.
What determines the amount of air resistance?
The shape and cross sectional area – also air density but that can’t be
changed.
How do you increase the amount of air resistance? When is this beneficial?
Make a cup shape as large as possible. Skydiving, drag racing, slowing down
the space shuttle.
What about the opposite of this?
A tapered tear-drop shape is the most aerodynamic shape.
Demo: ping-pong ball, parachute, dragster, space shuttle, paper balls
Terminal Velocity – the speed at which the weight of the object is equal to
its air resistance – the object no longer accelerates.
Video clips: sky diving
1. Two forces act on a book resting on a table: its weight and the support
force from the table. Does a force of friction act as well? What if the
table is tilted slightly so that the textbook still does not move?
No. There are no forces acting horizontally that want to move the textbook.
Yes. There is a force acting to pull the textbook sideways which is counteracted by a frictional force.
2. Suppose a high flying jet cruises with a constant velocity when the
thrust of its engines is a constant 80,000 N. What is the acceleration
of the jet? What is the force of air resistance acting on the jet?
A = 0 m/s2- constant vel. Air resistance = 80,000 N
Assignment Ch. 6:
8, 9, 16-20, 32, 52, 67
55
Why doesn’t a person get harmed while lying on a bed of nails?
The person’s weight is distributed to each nail which is not enough force to
cause the nail to pierce skin.
Pressure – (Pascals – N/m2) the force per unit area
American units = lbs./in2
P = F / A
What is the pressure exerted on the floor by a person standing straight up?
What is the pressure exerted on the floor by a person lying down?
What is the pressure exerted on the floor by a person standing in high heels?
Atmospheric Pressure – (14.2 lbs./in2 ~ 98,500 N/m2) fluid pressure due to the
weight of the air.
Video clips: can crush, tanker crush
1. How much force is being exerted on an area of 36 in2 by a pressure of
90lb./in2? 3240 lb.
2. The roof of a building is designed to withstand 14,000 N of force. The
roof of a building is 10 m long, and 5 m wide. What is the least amount
of pressure the roof must hold? 280 Pa
Due Activity: How much does your car weigh?
Assignment Ch. 6: 10-12, 24, 42, 43
56
Every car is supported by tires that are inflated with a specific amount of
air pressure. The air pressure supports the car on the ground over a certain
contact area. By measuring the contact area, called the foot print, and
measuring the pressure of each tire, you can calculate the weight supported
by the tires.
Calculate the weight supported by one of the front tires first:
Measure the width of tire tread = ___________ in.
Measure the length of the contact area by shoving two sheets of paper on
either side of the tire until they hit the where the tire contacts the
ground. Length of tire tread = __________ in.
Measure the tire pressure using a tire gauge. Pressure = ___________ lb./in 2
Be sure to subtract the normal atmospheric pressure of 14.2 lb./in2 – that
amount of pressure is already balanced before filling the tire.
Calculate the weight supported by the tire: (then x 2, two front tires)
Repeat this procedure for one of the rear tires:
Calculate the total weight of the car and compare it to the actual weight
listed on the driver door or from the manufacturer online. Compare the
results – explain any differences.
57
 Write down key terms with their definitions.
 Write down the equations used in the Chapter.
 Solve the following example questions:
1. What are the two parts to Newton’s 2nd Law?
2. What does Net-Force mean?
3. What are the two equilibrium conditions?
4. What does adding mass to an object do to its acceleration? Explain why.
5. Calculate the Net-Force acting on these objects, and then find their
accelerations.
a.
b.
20 kg
20 N
15 N
15 N
15 kg
10 N
30 N
10 N
55 N
6. If a net-force on an object is tripled what will happen to an object’s
acceleration?
58
7. If a mass is dumped on an object that triples the objects mass what will
happen to the object’s acceleration?
8. What happens to the value of an object’s acceleration while falling in
the presence of air resistance?
9. A jet with a mass of 10,000 kg is accelerating at what value when each
of its 2 jet engines produces a thrust of 7500N.
10.
When the jet from #9 is cruising at a constant velocity and
altitude with the jet engines running as stated. What is value of the
jet’s air resistance?
11.
What effect do snow shoes have in the winter? Why do they work?
12.
A tire has a standard pressure of 32 lbs./in2. If the foot print
of the tire on the ground is 5in. x 7 in. How much weight is this tire
supporting? If all tires are the same how much does this car weigh?
59
Chapter 7 Highlights:
Action-Reaction Pairs
Rockets
Key Terms
Interaction
Mass
Action-Reaction
Force
60
How does a rocket work?
Newton’s 3rd law.
What happens when a blown up balloon is released? Why does it do that?
The balloon pushes the air out, the reaction is the air pushes back on the
balloon. Due to the air’s inertia (mass).
What will happen to the students given these different situations?
They do in opposite directions with equal force.
Demos: 2 students pushing and pulling with different masses
Mass – (Newton’s definition) – inertia
 Which is an object’s resistance to change in motion
o More mass = more inertia = more resistance
When the students were on the carts:
Action:
Reaction:
Were they the same force? Yes. Forces always come in pairs.
Newton’s 3rd Law of Motion – for every action force there is an equal but
opposite reaction force.
 Force only exists when matter is present and requires 2 separate masses
– they compose an interaction pair –
Ex. The students make up an interaction pair. To find the reaction force from
the action force, just switch the terms of the objects. (Note: there is no
difference between action-reaction forces – they are indiscernable)
61
Ex.
Action: The Earth pulls on a ball.
Reaction: the ball pulls on the earth.
Action: You walk by pushing on the floor.
Reaction: the floor pushes on you.
Action:
Reaction:
Application to Newton’s 2nd Law:
What happened to the acceleration when the mass of one student was doubled?
The acceleration was decreased by half.
Force on student 1 = Force on student 2
F1 = F2
m
A
=
M
F1
a
Shooting a cannon:
Action:
Cannon pushes on ball.
Reaction: ball pushes on cannon*
*
Sometimes called recoil
F2
Calculate the acceleration of the cannon if the mass of the cannon ball is
5kg and accelerates at 1200 m/s2, and the cannon has a mass of 100 kg.
5 (1200) = 100 a
a = 60 m/s2
62
1. Does a stick of Dynamite contain force?
No. it contains energy. The release of this energy creates a force on its
surroundings.
2. A car accelerates along a road. Strictly speaking, what is the force
that moves the car? The road pushing on the tires.
3. We know that the earth pulls on the moon. Does the moon also pull on the
earth? If so, which pull is stronger? Yes. It is the same amount of
force. The earth doesn’t really move much due to its mass being much
larger than the moon’s.
4. Suppose a friend who hears about Newton’s 3rd law says that you can’t
move a football by kicking it because the reaction force by the kicked
ball would be equal and opposite to your kicking force. The net-force
would be zero, so no matter how hard you kick, the ball won’t move.
What is wrong with this logic? The force of your kick is acting on
separate masses, not the same mass. The net-force would be zero if it
were acting on the same mass but it isn’t.
Assignment Ch. 7: 1-11, 13, 14, 18, 24, 25, 28-30, 34-41, 54, 55
63
Chapter 8 Highlights:
Momentum
Impulse
Elastic and Inelastic Collisions
Law of Conservation of Momentum
Key Terms
Momentum
Elastic
Vectors
Impulse
Inelastic
Conservation of Momentum
64
Which would you rather do: try to catch a foam ball, or a shotput? Why?
Foam ball, it has less mass.
Which would you rather do: try to catch a foam ball thrown slowly or one that
is pitched? Why? the slow one. It has less motion.
Newton’s 1st Law of Motion – (inertia)- object at rest stays at rest, an
object in motion will stay in motion, unless acted on by an outside netforce.
Momentum – (kg.m/s)- describes inertia in motion, it is the product of mass
moving at a certain velocity.
 = m v
Is momentum a vector? Yes. Velocity is a vector so momentum is a vector.
Interpreting the equation;
Can a motorcycle have the same momentum as a full size car? Explain your
answer. Yes. If the motorcycle is moving much faster than the car or they are
both at rest.
In order to change the state of motion of an object what must be applied?
Force.
If the driver were to apply the gas lightly to accelerate up to 60 mph how
long would it take? It would take a long time.
If the driver in the previous question slammed on the gas to accelerate up to
60 mph, how long would the car take? It would take a short time.
Did the car undergo the same change in momentum in each of the previous
cases? Yes. The momentum change was the same.
65
Impulse – (kg.m/s) – change in momentum, it is the product of net-force and
time acting on an object.
J = F t
Is impulse a vector? Yes. Force is a vector so impulse is a vector.
Use the equation to describe the accelerating car situation:
A large force in a short period of time = a small force in a long period of
time.
Application and interpretation of the equation:
A desk sliding across the floor at 3 m/s slowly slides to a stop due to
friction. How long would the desk take to stop? How much force was acting on
the desk as it slid to a stop?
If the same desk were to stop by striking a wall, how long would it take for
the desk to stop? How much force acted on the desk?
Explain the differences and similarities in the previous example using
impulse and momentum:
Explain the momentum and impulse applications in the following demos:
Boxing, Air bags, Car safety, jumping off a platform, hammer on a nail.
Short impact time results in a large impact force. A longer impact time
results in a smaller impact force.
66
1. Calculate the momentum of a 1000 kg car moving at 20 m/s.
20,000 units
2. If a 5 kg shotput is to have the same momentum as the car in the
previous problem, how fast must it be traveling?
20,000 = 5 v, v = 4000 m/s
3. If a motorcycle, with a mass of 300 kg were to have the same momentum as
the car in #1, how fast must it be traveling?
20,000 = 300 v, v = 67 m/s
4. What impulse is needed to get the car from #1 moving at 20 m/s if it
started from rest? 20,000 units
5. What impulse is needed to stop the car from #1? -20,000 units
6. If you wanted to stop the car in 10 sec. How much force must the tires
supply? What is the origin of this force?
F t = 20,000, F = 2000 N, the frictional force between the road and
tires.
7. If the car were to suddenly stop, as in a car accident, in ½ second.
How much force acted on the car? What happens to a car in an accident?
F t = 20,000, F = 40,000 N, the tremendous force causes the car to crumple.
8. If an airbag increases the time of impact 5 times as much as without an
airbag, how much will an airbag decrease the force of impact? 5 times.
9. If a dish falls, will the impulse be less if it lands on a carpet than
if it lands on a tiled floor? Which one will most likely cause the dish
to break? Explain. Same impulse. The tile floor – less time of impact.
Assignment Ch. 8:
1-7, 9-11, 24-27, 35-46
67
Applications of Impulse and Momentum:
How do martial arts experts break wood with their bare hands?
Quick hands decrease the time of impact which increases the force of impact.
Demo: board breaking
Impulse – change in momentum.
Momentum – inertia in motion.
What happens when a concrete cinder block is struck by a fast moving sledge
hammer? It breaks due to the large momentum transfer and short impact time.
Demo: bed-o-nails
Why is it important that the concrete block have such a large mass?
The large mass resists the sudden change in motion due to the sledge hammer
and doesn’t move as much before breaking apart.
What is the impact time when doing either of these two demonstrations?
Impact time is short.
What does this tell you about the impact force?
Large impact force.
Is the impulse the same on the boards as on the hand? Yes. By Newton’s 3rd
law and the time of impact being the same for both.
Is the impulse the same on the block as it is on the hammer?
Yes. Same reason as above.
68
What is the difference between elastic and inelastic collisions?
Bouncing.
Elastic – objects collide and bounce apart – there is a transfer of momentum
between the objects which results in a larger impulse.
Inelastic – objects collide and stick together – the momentum is shared
between the masses.
What happens to the impulse when an object has an inelastic vs. elastic
collision? Impulse is smaller in inelastic collisions.
 Bouncing does not necessarily increase impact force, it involves
stopping and pushing back in the opposite direction.
Demo: exercise ball
Assignment Ch. 8:
12-14, 17, 47
69
What will happen to the velocities of the students after each of the
collision interactions? Inelastic collisions result in a slower velocity.
Elastic collisions result in the same or higher velocity.
Demo: students on carts with different mass
elastic and inelastic collisions
Law of Conservation of Momentum – the total momentum before a collision or
interaction must be equal to the total afterwards.
 No external forces acting on the system
 Elastic Collisions – momentum is exchanged between the objects
Demo: steel pendulums, rubber ball
 Inelastic Collisions – momentum is shared between the objects
Demo: catching rubber ball, playdoe glob
Examples: Calculate the velocities of the two car system after the following
collisions:
1.
v = 10 m/s
v = 0 m/s
1000 kg
2000 kg
inelastic collision
10,000 + 0 = 3000 v
V = 10,000/3000 = 3 1/3 m/s
70
2.
v = 10 m/s
v = 0 m/s
1000 kg
2000 kg
10,000 + 0 = 1000 (2) + 2000 v
v = 2 m/s
v =
?
m/s
elastic collision
10,000 – 2000 = 2000 v
8,000/2000 = v = 4 m/s
3.
v = 10 m/s
v =
?
m/s
1000
2000 kg
10,000 – 2000 v = 3000 (0)
v =
0
inelastic collision
2000 v = 10,000, v = 5 m/s
4. A train car with a mass of 5000 kg is traveling to the right with a
velocity of 5 m/s. It collides with two other connected cars of equal
mass at rest. If they collide and stick together, what is their final
velocity?
5000 (5) + 10,000 (0) = 15,000 v
25,000 = 15,000 v, v = 1.7 m/s
What is the change in momentum of each car in example #2? Are they the same?
Explain your answer. 8,000 units for each. The momentum lost by one was
gained by the other.
Assignment Ch. 8:
15, 16, 18, 50, 55-58, 60-62
71
 Write down key terms with their definitions.
 Write down the equations used in the Chapter.
Solve the following example questions:
1. What two quantities are involved in calculating momentum?
2. Can a car have the same momentum as a motorcycle? Explain.
3. What two quantities are involved in calculating impulse?
4. Why should a boxer ride with the punch? Why should the boxer try not to
move forward into an oncoming punch?
5. Why are cars designed with airbags, crumple zones, padded dash boards,
and stretchy seat belts? Explain using impulse and momentum change.
6. If impact time is increased 3 times what happens to the value of the
impact force?
7. If an applied force on a cart acts for 4 times longer than before, what
happens to the value of the cart’s final momentum as compared to
before?
8. Why wasn’t the teacher harmed when lying on the bed of nails and the
concrete block was busted on his chest?
72
9. Calculate the final velocity of the car and truck in the following
example. A car with a mass of 2000kg moving at 10 m/s collides with a
truck with a mass of 3000kg at rest. What will be the velocity of the
car and truck if they crash and stick together?
10.
Calculate the final velocity of the car and truck in the following
example. A car with a mass of 2000kg moving at 10 m/s collides with a
truck with a mass of 3000kg at rest. What will be the velocity of the
car and truck if they crash and bounce apart? The car continues to move
forward with a velocity of 2 m/s after the collision.
73
Chapter 32 Highlights:
Electrical Forces and Charges
Law of Conservation of Charge
Methods of Charging
Conductors and Insulators
Coulomb’s Law
Key Terms
Charge
Conductor
Insulator
EM Force
Grounding
Electrostatic
Polarization
Conservation of Charge
Coulomb
Induction
Superconductor
Semiconductor
74
What are the four natural forces?
1. Gravity – force of attraction between masses.
2. Electromagnetic – (EM) – force of attraction or repulsion between
charges.
3. Strong Nuclear – holds nucleus together.
4. Weak Nuclear – governs radioactivity.
Discussion: Find objects around the room that use the electromagnetic (EM)
force in some way: The EM force is responsible for electricity – EM energy –
it is, technically speaking, responsible for holding atoms together.
Where do we find the EM force? Everywhere.
What does the EM force do? Holds all atoms together, EM radiation is light,
radio, etc.
What is the source of the EM force?
Charges
electron
Charges – (2 kinds) (units = Coulombs = C)
neutron
Carriers of the EM force.
1. Positive charges origin: protons
proton
2. Negative charges origin: electrons
75
Atomic Particles – small particles that compose all atoms - proton, neutron,
and electron.
 Neutrons – particles that exist within the nucleus and have no-net
charge.
1. Every atom has a positively charged nucleus composed of protons and
neutrons surrounded by negatively charged electrons.
2. All electrons are identical: that is each has the same mass and the same
quantity of negative charge as every other electron.
3. The nucleus is composed of protons and neutrons. (except for the common
form of hydrogen)
4. All protons are identical; similarly, all neutrons are identical.
5. A proton has nearly 2000 times the mass of a electron, but its positive
charge is equal but opposite to the charge of the electron.
6. A neutron has a slightly larger mass than a proton and has no netcharge.
7. Atoms usually have as many protons and electrons, so the atom has a zero
net-charge.
like charges repel and unlike charges attract.
Fundamentally charge is quantized, that is charge has specific set amounts,
or integers of 1.6 x 10-19 C.
Demo: pithballs, electrographs, rods + cloth
1 Coulomb of charge = 6.25 x 1018 electrons
Ex. Draw a Helium Atom and label the fundamental atomic particles:
Assignment Ch. 32: 1-7, 12
76
Have you ever scuffed your feet across a carpeted room on a dry winter day
and then touched someone? What happens? Why does it do this?
You shock the other person. A build-up of electrons occurred on your body and
discharged it to the other person.
What happens when a rubber balloon is rubbed on a sweater or someone’s hair?
Why does it do this? Why does it attract other things?
It strips lose electrons from the sweater. It will cause an opposite charge
in another object and be attracted.
Atoms are normally neutral, that is, they have no net-charge. How do we get
charged objects? We have to remove electrons somehow.
Where does this charge come from? The charge was always present in the
electrons and protons – you’re simply moving electrons.
Law of Conservation of Charge – charge is neither created or destroyed only
transferred from one object to another. The net-charge of the universe = 0
Separation of Charge – the removal of electrons from one object to another
causing charged objects – protons do not move they are locked in the nucleus.
Conductors – usually metals – have loosely bound outer electrons in their
atoms that are allowed to move freely from atom to atom throughout the metal.
Ex. Silver – best conductor, copper is second best then gold
Insulators – materials that have tightly bound outer electrons – those
electrons can’t be transferred because they are involved in binding the
atoms together.
Ex. glass, plastic, wood, etc.
77
Ion – atoms that have lost or gained electrons.
 Positive Ion – lost electrons and has a net-positive charge.
 Negative Ion – gained electrons and has a net-negative charge.
Ex. Sodium Ions:
Na+ ; lost 1 electron
Na- ; gained 1 electron
Na+2 ; lost 2 electrons
78
1. Charging by Friction – rubbing two different materials together loosens
a few outer electrons
 Charges are stripped from the surface and are attracted to one of the
objects more than the other by the properties of the materials.
 Main method of charging
Demo: fur and rubber rod
2. Charging by Conduction – (contact) – touching a charged object to a
neutral object causes charge to flow from one to other until they are at
the same voltage – normally 0 V – neutral.
Demo: _____________ touches the charged VandeGraff generator
3. Induction – (4 basic ways) using a charged object to cause a charge
build-up on another object without a charge transfer between the two.
Demos: VandeGraff generator and electroscope
a. Induced Polarization:
i. Ex. Balloon on wall, comb on paper
Normal neutral atom
electron cloud distorted by negative charge
in the wall
one side is slightly more positive than the other and attracts the
closer negative charge (balloon)
b. Polarization:
i. Ex. Water and charged tube
Polarized water molecule
water orients itself with presence of a negative charge (tube)
with the positive side facing the negative charge (tube) and
they are attracted
79
Note: The last two methods of charging do not involve touching the original
charged object, therefore and charge can be generated an infinite number of
times using these methods. The last two methods also involve the use of a
metal conductor.
c. Separation of Charge with Grounding:
A conducting sphere is
brought near a positively
charged generator
1. The free electrons in the metal
sphere are attracted toward the
generator, polarizing the metal
sphere
2. A ground wire is brought in
and touches the metal sphere.
Extra electrons from the ground
are attracted to the positive of
the metal sphere.
3. The ground wire is then removed
in the presence of the positive field
of the generator
4. The metal sphere now
has excess electrons
trapped from the
ground. It has a negative
charge.
Grounding
– connecting an object to a
large source of free electrons that can
give or take electrons without changing its
neutral charge. i.e. the earth, a large
metal object
80
d. Separation of Charge without Grounding:
Two conducting spheres are
brought near a positively charged
generator while touching creating a
connection between the spheres.
1. The free electrons in the metal
spheres are attracted toward the
generator, causing those electrons
to collect in the sphere closest to
the generator
2. The spheres are then separated in
the presence of the positive field of
the generator
3. The excess electrons are
trapped in the left sphere. It
has a negative charge. The
right sphere has lost
electrons. It has a positive
charge.
Video: Lightning Electric Skies
Assignment Ch. 32: 8-10, 16, 17, 20-22, 31-38
81
What happens to the hair when a charged balloon is brought near and away?
It will attract the hair more strongly when it is closer.
Why does the balloon or any other charged object attract other neutral
objects? It will induce an opposite charge and be attracted to it.
Why do these two charged balloons repel one another? What happens to the
other balloon when one balloon is brought closer? They have about the same
amount of charge and are negative. It repels more strongly.
What determines the amount of force in each of these situations?
The amount of charge and the distance between the charges.
Charge – (Q) – is the carrier of the EM force, the more charge – the more
force.
Inverse Square Law – field laws obey this rule of that a field drops by the
square of the distance of separation.
Demo; flashlight on wall, VandeGraff generator and electroscope
Coulomb’s Law – the electric force between two charges is directly
proportional to the product and inversely proportional to the square of the
distance of separation.
FE = kq1q2
d2
 Electric field constant, k = 9.0 x 109 N.m/C2
 compared to gravity’s field constant, G = 6.67 x 10-11
 EM force is 1020 times stronger than gravity!
Examples: Remember force is a vector!
+0.0001 C
-0.00002 C
+0.0003 C
+0.0003 C
A
B
C
D
20 cm
10 cm
1. What is the force acting between charge A and B?
-450 N, an attractive force
2. What is the force acting between charge C and D? 81,000 N, repulsive
82
1. What is the chief significance of the fact that G in Newton’s law of
gravity is a very small number, whereas, k in Coulomb’s law is a very
large number? Electric force is many many times stronger than gravity.
2. The amount of electric force acting between charges in your body is
tremendous, whereas the gravitational force is very small, so why do we
feel the gravitational force and not the electrical? Everything is
normally neutral. No-net force between objects.
3. If an electron at a certain distance from a charged particle is
attracted with a certain force, how will the force compare at twice this
distance? Three times? Half? 4 times less, 9 times less, 4 times as much
4. What are the charges in the particles in question #3? – and +
5. If a negative charge is a certain distance from a positive charge. How
will the force compare if:
a. The negative charge were doubled? 2 times greater
b. The positive charge were doubled? 2 times greater
c. If both charges were doubled? 4 times greater
d. If the distance between them were doubled, and both charges were
doubled? It would be the same amount of force.
Assignment Ch. 32:
11, 13, 27-30, 47
83
 Write down key terms with their definitions.
 Write down the equations used in the Chapter.
Solve the following example questions:
1. What is the charge of a proton, electron, and a neutron?
2. A plastic rod rubs on a polyester sheet and attains a positive charge,
what is the charge of the sheet? Explain why.
3. What physical property makes a good conductor? A good insulator?
4. Explain the three methods of charging?
5. Explain how a normally neutral object can be attracted to a charged
object.
6. A negative charge is brought near a conducting sphere but not touching.
If the sphere is then grounded, what is the charge of the conductor?
7. How are the three methods of charging involved in the formation of
lightning?
84
8. How does a lightning rod work?
9. How large is the electrical force compared to the gravitational force?
10.
Why don’t we normally feel the effects of the electrical force
but we constantly feel the gravitational force?
11.
By how much is the electrical force between charges changed if
their separation distance is doubled? Tripled? Cut in half?
12.
By how much is the electrical force changed if one of the charges
is doubled? Both are doubled?
13.
By how much is the electrical force changed if both charges are
doubled and the distance of separation is doubled?
85
Chapter 34 Highlights:
Flow of Charge
Ohm’s Law
Source of Electrons
Electric Power
Class Activity:
Electric Cooking with
Julia Childs
Key Terms
Current
Volts
AC Current
DC Current
Ohm
Potential Difference
Ampere
Electric Power
Voltage Source
Conduction Electrons
86
What happens to a ball that is above the floor and is released? Why does it
do this? It falls downward. A force on the ball’s mass pulls it down.
Demo: ball drop
What happens to the water in the PVC tube when the tube is tilted? Why does
it do this? Gravity pulls the water downward and creates pressure on the
water inside.
Demo: PVC tube with water
What happens to the flow when it is tilted higher? Explain.
Higher flow due to higher pressure
What happens when you try to touch the VandeGraff generator when it is
charged? Why does this happen?
You get shocked due to the electrons flowing into you.
What causes the electrons to flow?
The push due to a build-up of charge - electrons repel one another.
What are you in this whole model of an electrical connection?
You are the conductor.
What is the floor (ground) in this model?
The neutral, low potential. Has no extra electrons.
What is the generator in this model?
The high potential, has unbalanced electrons.
Electric Circuit – A pathway (usually a conductor) that allows the electrons
to flow to a lower voltage (usually neutral).
Electric Potential Difference – (Volts or Voltage)- relates the amount of
energy per unit charge an electron will have across an electric circuit.
 Established across a circuit = “electric pressure”
What relation do the examples above have to the electrons in the VandeGraff
generator? The build-up of electrons on the generator want to push each other
off creating a voltage, you try to touch it, you become the conductor which
causes the charge to flow to the earth (neutral or 0 V).
87
Electric Current – (A) (Amperes or Amps) – the flow of electrons through a
circuit per unit time due to a potential difference.
I = Charge/time = Q/t
 Established through a circuit.
 1 C = 6.25 billion billion electrons
 1 Amp = 1 Coulomb / 1 second
Sources of Electric Current (Voltage)
1. Battery
Involves: chemical reactions strips electrons from metals
2. generator Involves: mechanical energy does work to drive electrons
through wires using magnets
3. solar cell Involves: converts light into electric current using semiconductors
Why don’t charges flow immediately like when getting a “shock” from the
generator? Different materials have a different electric resistance.
Electric Resistance – (Ohms – ) – a measure of how easily electrons can
flow through an object or circuit.
 Resistance varies by 4 basic things:
1. Type of materials: metals have least resistance
2. Thickness: thicker materials have more available electrons per crosssectional area – similar to water pipes.
3. Length: longer wires interact more with the flow of the electrons
4. Temperature: hotter temp. creates more resistance due to the electrons
in the wires transmitting heat energy rather than electrons.
Demo: slinky’s resistance, student resistance
88
What happens when an electric current is passed through a resistance?
the resistor heats up.
Why does it do this? Explain in terms of electrons transferring.
Each electron/atom interaction loses a little energy as heat.
Demo: resistor, fuses and heat
Resistance values chart:
Black Brown
0
1
Red
2
Orange Yellow Green Blue Violet Gray White
3
4
5
6
7
8
9
AB x 10C
Band 1 (A)
Band 2 (B)
Band (C)
Brown
Black
Red
Resistance
Value
1000
Red
Red
Yellow
220,000
Assignment Ch. 34:
RQ 1-6, 8-11, 31,32, 41-43
89
When a student is connected into a simple circuit with a generator, what
happens to the current through the student when the voltage is increased?
Why? The current goes up due to the voltage increase which increases the
electric pressure.
When a student is connected into the same circuit with the generator and
another student what happens to the current through the students? When more
students are added? Why does it do this? The current decreases. The electrons
have to travel through both students – increasing electric resistance.
Ohm’s Law – the current through a circuit is equal to the value of the
applied voltage and inversely related to the circuit’s resistance.
 Assumes a constant resistance for different voltages
 Light bulbs do not obey Ohm’s law – increasing voltage, increases the
bulb’s resistance because of an increase in temperature.
o Light bulbs do however obey the Law at specific voltages and it
can be used to calculate the current or resistance at that
voltage.
V
I
R
Demo: bulb and power source
What happens to the bulb’s brightness when the voltage is turned up?
It gets brighter – more current.
What happens to the bulb’s brightness when more light bulbs are added to the
circuit?
Gets dimmer – less current - more resistance.
What can you conclude about the current flowing through the bulb in each
case? As the voltage increases – current increases; As the resistance
increases – current decreases.
90
1. An automobile headlight with a resistance of 8 is placed across a 12V
battery. What is the current through the headlight?
I = 12 / 8 = 1.5 A
2. A flashlight with a 6 V lantern battery has a current of 1.125 A. What
is the resistance value of the light bulb at that voltage?
R = 6 / 1.125 = 5.33 
3. A student with a resistance value of 16,000 has a current of 0.008 A
flowing through him. What is the voltage across the student?
V = 0.008 * 16,000 = 128 V
1. What is the resistance of an electric stove that draws 12 A of current
when connected to a 120 V outlet?
R = 120 / 12 = 10 
2. How much current is drawn by a lamp that has a resistance of 100 
when a voltage of 50 V is impresses across it?
I = 50 / 100 = 0.5 A
Assignment Ch. 34:
12-14, 33-36, 50
91
When a voltage is impressed across both ends of a wire, what happens to the
electrons in the wire?
They start to move.
Are all electrons the same?
Yes.
Are all of the electrons in a circuit being provided by the battery or
generator?
No. electrons in the wire are also involved.
What happens when an electron is used by the battery in the circuit?
The electron is taken in (-) to complete the chemical reaction.
Demo: student/electron wire model
Conduction Electrons – the electrons in the outer orbit(s) in the conducting
material that move throughout the conductor.
 Speed of electrons = 0.01 cm/s
 Speed of energy transfer = 1,500,000 m/s
Note: increasing the voltage does not increase the speed of the electrons, it
will only influence more electrons to conduct due to the wire’s electrical
resistance!
Demo: generators and batteries
Alternating Current – (AC) generating source that causes the electrons to
move in opposite directions every moment in time
Ex. 60 Hz – American standard, AC generator
Direct Current – (DC) – source has electrons flowing in one direction.
Ex. batteries, some generators, capacitors
92
What do the numbers at the top of selected light bulbs tell you?
Power.
Ex. Different light bulbs
Electric Power – (Watts) the amount of electric energy used per unit time.
 Energy is in units of Joules = J
Electric Equations for Power:
P = I V
P =I2R
P = V2/R
Energy dissipated by electric current:
E = P t
Calculate the energy dissipated by a 40 W bulb in 2 hours:
E = 40 * 2 * 3600s = 288,000 J
Which of these bulbs have more resistance and current? Assume they are across
a 120 V outlet.
Power (W)
7.5
15
40
90
200
Resistance
()
Current (A)
1920
960
360
160
72
0.0625
0.125
0.333
0.75
1.67
93
What can you conclude about the thickness of their filaments?
Higher wattages have a thicker filament – less resistance
How much energy does a 60 W light bulb use in a day?
E = 60*24*3600 = 5,184,000 J
Why do power companies use kilowatt-hours to charge for electricity used?
Joules is a very small unit of energy. kWh is a much larger unit.
Kilowatt-Hours – unit of energy used by power companies to charge $. Not a
scientific or SI unit.
How is electricity transmitted to your homes?
Thick wires carry large amounts of electric current to reduce resistance.
Why would the transmission of energy to your home be at high voltages and low
currents? Hint: recall power equation #2, current determines heat energy
loss. Current produces heat – less current results in less heat energy lost.
Assignment Ch. 34: 37, 40, 55, 57, 62, 66, 74
94
 Write down key terms with their definitions.
 Write down the equations used in the Chapter.
 Solve the following example questions:
1. What causes an electric current?
2. What is the unit of electric current?
3. Does charge flow through a circuit or into a circuit?
4. Does voltage flow through a circuit, or is voltage established across a
circuit?
5. Is electric resistance greater in a short fat wire, or a long thin wire?
6. For a constant resistance, if the voltage across a circuit doubles, what
happens to the current in the circuit?
7. For a constant voltage, if the resistance doubles, what happens to the
current in the circuit?
8. Calculate the current through a circuit if 10 Coulombs of charge flow
through it in 5 seconds.
9. Calculate the current in a toaster that has 10  of resistance when
connected to a 120 V source.
95
10.
Calculate the voltage across a 100  resistor with a current of
0.25 A.
11.
Calculate the power of the toaster in #9 and the resistor in #10.
12.
Calculate the energy dissipated by the toaster in #9 if it takes 1
min. to toast the bread.
13.
Calculate the energy dissipated by the resistor in #10 if current
flows through it for 2 ½ min.
96
Chapter 35 Highlights:
Schematic diagrams
Series Circuit Properties
Applying Ohm’s Law and Power
to Series Circuits
Parallel Circuit Properties
Applying Ohm’s Law and Power
to Parallel Circuits
Compound Circuits
Key Terms
Circuit
Parallel
Voltage
Current
Switch
Schematic Diagram
Series
Resistance
Fuse
97
What happens when
It gives off 25 W
What happens when
another bulb? The
one 25 W bulb is connected to 120 V?
of light
another 25W bulb is connected in series to 120V? And
bulbs don’t glow as brightly
Why does it do this? The circuit has more resistance.
What is a Series circuit? A circuit that creates only one current loop that
connects the high to the low potential.
There are two basic kinds of circuits. The first most basic kind of circuit
is the series circuit. The schematic diagram below shows two light bulbs
connected in series.
Schematic Diagram – a visual “map” of the design of a circuit – a
blueprint.
E
 Simple schematic symbols:
What do these symbols mean for schematic diagrams?
E
What would be the electrical properties of a series circuit?
Do Activity: Series Circuits
98
Explore the electrical properties of series circuits by using 4
identical flashlight bulbs and a variable voltage source.
You will be using light bulb sockets and wires with alligator clip connectors
to assemble the simple series circuit as shown below in the schematic
diagram. The clips allow you to disconnect or add light bulbs into the
circuit easily.
When connecting the power supply to your circuit be sure your voltage source
is set to 6 DCV. DO NOT SET THE POWER SUPPLY TO A VOLTAGE GREATER THAN 6 V.
This may cause too much current through the power supply and light bulbs
which will damage the equipment.
Measuring the volts used by each light bulb: Set your small red multi-meter
to “10 DCV” place each probe on either side of the light bulb you are
measuring. The display will show the volts used – ignore any negative values
the display may have.
Measuring the current used by the circuit: Set the larger multi-meter to the
highest amperage setting “20 DCA.” One probe should be connected to the
black “ground” connection, and the other probe should be connected to the
far left connector labeled “20 A.” To measure the current, the multi-meter
needs to be connected in series with the rest of the circuit as shown in the
schematic diagram – ignore any negative values the display may have.
(Note; the wires will add a small amount of resistance)
E
A
99
1. With the power source on, measure the current of the circuit as
indicated by the ammeter. Record the measurement in the table below.
2. Measure the volts used by each of the light bulbs by using the
voltmeter. Touch each probe to the lamp base connections on either side
of the light bulb. Record the measurement in the table below. Repeat
this for each of the lamps in the circuit.
3. Remove one of the lamp sockets from the circuit so there are 3 lamps
connected in series. Repeat steps 1 and 2 above and repeat this step for
the remaining lamps in the circuit until there is only one lamp
remaining.
Number of
bulbs
Total
Current
(A)
Total
Circuit
Volts (V)
4
6
3
6
2
6
1
6
Voltage Across Each Lamp (V)
4. Repeat the above procedure using a 3 DCV power supply setting rather
than a 6 DCV power supply setting.
Number of
bulbs
Total
Current
(A)
Total
Circuit
Volts (V)
4
6
3
6
2
6
1
6
Voltage Across Each Lamp (V)
100
5. Reconstruct the 6 V circuit with 4 lamps in series with the power on;
Take an extra wire and clip the wire across one of the lamps. What happens to
the light bulb? Why does it do this?
Remove the extra wire from the circuit. Without removing the socket from the
circuit, unscrew one of the light bulbs from the base. What happens to the
brightness of the other lamps? Why does it do this?
1. Was there any change in the brightness as the number of light bulbs in
the circuit decreased? Explain your answer.
2. How are the volts across each light bulb related in each of the tested
circuits?
3. What relationship do you see between the volts used by the bulbs in the
circuit to the voltage of the entire circuit?
4. What happened to the current in the circuit as the number of light bulbs
decreased? Explain your answer.
101
5. What do you think is happening to the resistance of the circuit as the
number of light bulbs in the circuit is decreasing?
6. Was there a change in the above circuit properties when 3 V was used in
the circuit rather than 6 V?
7. What relationship do you see between the currents in the 6 V circuit to
the currents in the 3 V circuit? Explain your findings.
102
A 25 W bulb is connected in series with a 60 W bulb. Which of these two bulbs
will shine the brightest when connected to 120 V?
The 25 W bulb –
Why did the light bulbs so this?
it had the most resistance so a larger % of the voltage was used.
What happens to the light bulbs when one of them is unscrewed from its
socket?
They go out.
Why did it do this?
There is a broken circuit.
The properties of a series circuit can be summarized below;
1. Electric current has one single pathway through the circuit. This means
that the current passing through each electrical device is the same.
2. The current is influenced by the resistance of each of the resistors, so
that the total resistance of the circuit is equal to the sum of all the
resistance.
3. Ohm’s law applies to each of the resistors in the circuit. The voltage
drop or the volts used by each resistor depends directly on the value of
their resistance. That means that a larger resistor will proportionally
use more volts than a smaller resistor.
4. The sum of the volts used by each of the resistors is equal to the
voltage impressed across the circuit.
I = V/R
Given the schematic diagram and a 40 V battery;
30 10 
Find the resistance of the circuit, current
through the circuit, and the volts used by
each resistor.
103
Given this schematic diagram;
10 
20 
30 
120 V
1. Find the equivalent resistance of this series circuit.
2. Find the current through the series circuit
3. Find the voltage drop across each resistor.
4. Compare the individual voltages to the total voltage of the circuit.
Does the property of a series circuit and voltage true?
Do activity: Testing Series Circuits
Assignment Chapter 35:
1-5, 19, 21-23, 35, 39
104
Using the resistors from the bin, construct 3 different series circuits, using 3 resistors
connected to 6 DCV. DO NOT GO OVER 6 DCV FOR HEALTH AND SAFTEY REASONS! RESISTORS MAY BECOME VERY
HOT AND EMIT HARMFUL VAPORS!
Fill in the following data tables. Calculate the equivalent resistance of your circuits, calculate
the current through the circuit, and calculate the voltage drops across each resistor. Then
measure the values from your circuit to verify your calculations. Note; values may be off due to
the wires adding a small amount of resistance.
Series Circuit 1
Resistor 1
()
Resistor 2
()
Resistor 3
()
Total
Resistance
()
Calculated
Current (A)
Measured
Current (A)
Calculated
Current (A)
Measured
Current (A)
Calculated
Current (A)
Measured
Current (A)
Resistance Value
Calculated Volts
for each
resistor
Measured Volts
for each
resistor
Series Circuit 2
Resistor 1
()
Resistor 2
()
Resistor 3
()
Total
Resistance
()
Resistance Value
Calculated Volts
for each
resistor
Measured Volts
for each
resistor
Series Circuit 3
Resistor 1
()
Resistor 2
()
Resistor 3
()
Total
Resistance
()
Resistance Value
Calculated Volts
for each
resistor
Measured Volts
for each
resistor
105
What happens when one 25 W bulb is connected to 120 V?
It gives off 25 W of light.
What happens when another 25W bulb is connected in parallel to 120V? And
another bulb?
They both give off 25 W of light. They shine equally bright.
Why does it do this?
Each one is getting the same voltage.
What is a parallel circuit? A circuit that has many current pathways, or
branches, that connect the high to low potential.
E
What would be the electrical properties of a parallel circuit?
Do Activity: Parallel Circuits
106
Explore the electrical properties of parallel circuits by using 4
identical flashlight bulbs and a variable voltage source.
You will be using light bulb sockets and wires with alligator clip connectors
to assemble the simple parallel circuit as shown below in the schematic
diagram. The clips allow you to disconnect or add light bulbs into the
circuit easily.
When connecting the power supply to your circuit be sure your voltage source
is set to 6 DCV. DO NOT SET THE POWER SUPPLY TO A VOLTAGE GREATER THAN 6 V.
This may cause too much current through the power supply and light bulbs
which will damage the equipment.
Measuring the volts used by each light bulb: Set your small red multi-meter
to “10 DCV”place each probe on either side of the light bulb you are
measuring. The display will show the volts used – ignore any negative values
the display may have.
Measuring the current used by the circuit: Set the larger multi-meter to the
highest amperage setting “20 DCA.”One probe should be connected to the
black “ground”connection, and the other probe should be connected to the
far left connector labeled “20 A.”To measure the current, the multi-meter
needs to be connected in series with the rest of the circuit as shown in the
schematic diagram – ignore any negative values the display may have.
(Note: the wires will add a small amount of resistance)
E
A
107
1. With the power source on, measure the current of the circuit as
indicated by the ammeter. Record the measurement in the table below.
2. Measure the volts used by each of the light bulbs by using the
voltmeter. Touch each probe to the lamp base connections on either side
of the light bulb. Record the measurement in the table below. Repeat
this for each of the lamps in the circuit.
3. Remove one of the lamp sockets from the circuit so there are 3 lamps
connected in series. Repeat steps 1 and 2 above and repeat this step for
the remaining lamps in the circuit until there is only one lamp
remaining.
Number of
bulbs
Total
Current
(A)
Total
Circuit
Volts (V)
4
6
3
6
2
6
1
6
Voltage Across Each Lamp (V)
4. Repeat the above procedure using a 3 DCV power supply setting rather
than a 6 DCV power supply setting.
Number of
bulbs
Total
Current
(A)
Total
Circuit
Volts (V)
4
6
3
6
2
6
1
6
Voltage Across Each Lamp (V)
108
5. Reconstruct the 6 V circuit with 4 lamps in parallel with the power on:
Take an extra wire and clip the wire across one of the lamps. What happens to
the light bulb? Why does it do this?
Remove the extra wire from the circuit. Without removing the socket from the
circuit, unscrew one of the light bulbs from the base. What happens to the
brightness of the other lamps? Why does it do this?
1. Was there any change in the brightness as the number of light bulbs
in the circuit decreased? Explain your answer.
2. How are the volts across each light bulb related in each of the
tested circuits?
3. What relationship do you see between the volts used by the bulbs in
the circuit to the voltage of the entire circuit?
4. What happened to the current in the circuit as the number of light
bulbs decreased? Explain your answer.
109
5. What do you think is happening to the resistance of the circuit as
the number of light bulbs in the circuit is decreasing?
6. Was there a change in the above circuit properties when 3 V was used
in the circuit rather than 6 V?
7. What relationship do you see between the currents in the 6 V circuit
to the currents in the 3 V circuit? Explain your findings.
110
A 25 W bulb is connected in parallel with a 60 W bulb. Which of these two
bulbs will shine the brightest when connected to 120 V?
60 W.
Why did the light bulbs so this?
Both are getting the same voltage, therefore they are 25 W and 60 W.
What happens to the light bulbs when one of them is unscrewed from its
socket?
The other stays lit.
Why did it do this?
Each branch is its own separate circuit.
The other simple circuit is called a parallel circuit. A parallel circuit has
properties that are opposite to those of the series circuit.
The properties of a parallel circuit can be summarized below:
1. Each resistor connects the two terminals of the power source by ladder
like branches of wires. The voltage applied across these branches is the
same voltage applied to each resistor.
2. The total current supplied by the power source divides among the
parallel resistors in the circuit. Ohm’s law applies to each of the
resistors and draws its current from the source. The currents from each
of the resistors added together is equal to the total current drawn from
the source.
3. Each resistor creates a branch or a new pathway for the current flow,
decreasing the overall resistance of the circuit. This means that the
total resistance of the circuit is always less than one resistor or
combination of resistors in the parallel circuit. The relationship of
resistance in a parallel circuit can be given by the following equation:
𝟏
𝑹𝑻
=
𝟏
𝑹𝟏
+
𝟏
𝑹𝟐
+
𝟏
𝑹𝟑
+⋯
111
I = V/R
Given the schematic diagram and an 40 V battery:
30 
10 
Find the resistance of the circuit, current through the circuit, and the
volts used by each resistor.
Given this schematic diagram:
30 
30 
30 
120 V
1. Find the equivalent resistance of this parallel circuit.
2. Find the current through each resistor.
3. Find the current from the power supply.
4. Compare the individual currents to the total current of the circuit.
Does the property of a parallel circuit and current true?
Do activity: Testing Parallel Circuits
Assignment Chapter 35:
6-11, 24, 30-34, 36, 38, 39, 42, 51, 55
112
Using the resistors from the bin, construct 3 different parallel circuits, using 3 resistors
connected to 3 DCV. DO NOT GO OVER 3 DCV FOR HEALTH AND SAFTEY REASONS! RESISTORS MAY BECOME VERY
HOT AND EMIT HARMFUL VAPORS!
Fill in the following data tables. Calculate the equivalent resistance of your circuits, calculate
the current through the circuit, and calculate the current of each resistor. Then measure the
current for your circuit to verify your calculations. Note: values may be off due to the wires
adding a small amount of resistance.
Parallel Circuit 1
Resistor 1
()
Resistor 2
()
Resistor 3
()
Total
Resistance
()
Calculated
Current (A)
Measured
Current (A)
Calculated
Current (A)
Measured
Current (A)
Calculated
Current (A)
Measured
Current (A)
Resistance Value
Calculated
Current for each
resistor
Parallel Circuit 2
Resistor 1
()
Resistor 2
()
Resistor 3
()
Total
Resistance
()
Resistance Value
Calculated
Current for each
resistor
Parallel Circuit 3
Resistor 1
()
Resistor 2
()
Resistor 3
()
Total
Resistance
()
Resistance Value
Calculated
Current for each
resistor
113
More complex circuits combine series and parallel parts together. They can be
as small as a 3 resistor circuit or as complex as a super-computer. However
complex the circuit may be, it can be broken down into simplified series and
parallel circuits.
Given the three light bulbs in the sockets - One is 60 W and the other two
are 25 W. The 60 W bulb is placed in series with the other two bulbs in
parallel. When placed in a 120 V circuit, which bulb shines the brightest?
a. 25 W bulb
b. 60 W bulb
c. Neither, they all are about equally bright
Why does this occur? The two 25 W bulbs have about 2x the resistance of the
60 W bulb. When the 25’s are connected in parallel their overall resistance
= the 60 W. So they all shine with equal brightness.
Ex. 1.
10 
=
? 20
=
? 5
10 
Ex. 2.
10 
10 
10 
Ex. 3.
=
10 
? 25
10 
10 
114
Given a complex circuit:
25 
25 
50 
10 V
50
Step 1:
Redraw the circuit as a group of
resistors along one side of the
circuit
50 
25  
10 V
50 
Step 2:
Identify components in series (if any)
and calculate their equivalent resistance
50 
25  
10 V
50 
115
50 

50 
10 V
Step 3:
Identify components in parallel, and
calculate their equivalent
resistance
50 
50
10 V
50 
50


25
10 V
116
Step 4:
Repeat steps 2 and 3 until the
resistors in the circuit are reduced
to a single equivalent resistance
75
10 V
Now you can apply Ohm’s Law to the circuit to calculate the current drawn
from the source:
I = 10/75 = 0.13 A
10 
Ex. 4.
10 
15 
10 


=
? 15
30 
If this circuit is connected to a 45 V source, how much current will be drawn
from the power supply?
I = 45 / 15 = 3 A
Do Activity: Testing Compound Circuits
Assignment Ch. 35: 40, 52, 54
117
Using the resistors from the bin, construct 3 different compound circuits, using 4 resistors
connected to 3 DCV. DO NOT GO OVER 3 DCV FOR HEALTH AND SAFTEY REASONS! RESISTORS MAY BECOME VERY
HOT AND EMIT HARMFUL VAPORS!
Fill in the following data tables. Calculate the equivalent resistance of your circuits, and
calculate the current through the circuit. Then measure the current for your circuit to verify
your calculations. Note: values may be off due to the wires adding a small amount of resistance.
Compound Circuit 1
Resistor
1 ()
Resistor
2 ()
Resistor
3 ()
Resistor
4 ()
Total
Resistance
()
Calculated
Current
(A)
Measured
Current
(A)
Calculated
Current
(A)
Measured
Current
(A)
Calculated
Current
(A)
Measured
Current
(A)
Resistance
Value
Draw your compound circuit:
Compound Circuit 2
Resistor
1 ()
Resistor
2 ()
Resistor
3 ()
Resistor
4 ()
Total
Resistance
()
Resistance
Value
Draw your compound circuit:
Compound Circuit 3
Resistor
1 ()
Resistor
2 ()
Resistor
3 ()
Resistor
4 ()
Total
Resistance
()
Resistance
Value
Draw your compound circuit:
118
 Write down key terms with their definitions.
 Write down the equations used in the Chapter.
 Solve the following example questions:
1. What causes an electric current?
2. What is the unit of electric current?
3. Does charge flow through a circuit or into a circuit?
4. Does voltage flow through a circuit, or is voltage established across a
circuit?
5. Is electric resistance greater in a short fat wire, or a long thin wire?
6. For a constant resistance, if the voltage across a circuit doubles, what
happens to the current in the circuit?
7. For a constant voltage, if the resistance doubles, what happens to the
current in the circuit?
8. Calculate the current through a circuit if 10 Coulombs of charge flow
through it in 5 seconds.
9. Calculate the current in a toaster that has 10  of resistance when
connected to a 120 V source.
10.
Calculate the voltage across a 100  resistor with a current of
0.25 A.
119
11.
If three lamps of equal resistance are connected in series to a 9
volt battery, what is the amount of voltage across each lamp?
12.
If three lamps of equal resistance are connected in parallel to a
9 volt battery, what is the amount of voltage across each lamp?
13.
What happens to the total resistance in a series circuit as more
resistors are added to the circuit?
14.
What happens to the total resistance in a parallel circuit as more
resistors are added to the circuit?
15.
What kind of circuit is used in your home? Why?
16.
Draw a schematic diagram of a series circuit with 3 resistors with
values: 5 , 10 , 15 , connected to a 60 V source.
17.
Calculate the total resistance of the series circuit, and then
find the current through the series circuit in #16.
18.
Draw a schematic diagram of a parallel circuit with 3 resistors
with values: 60 , 60 , 60 , connected to a 120 V source.
19.
Calculate the total resistance of the parallel circuit, and then
find the total current from the power source in the parallel circuit in
#18.
20.
On the back, draw a compound circuit using 4, 10 resistors, then
calculate its equivalent resistance and current if it is connected to
20V.
120
Chapter 36+37 Highlights:
Magnetic Poles
Magnetic Fields
Magnetic Domains
Electromagnetism
Electromagnetic Induction
Generators
Transformers
Key Terms
Current
Electromagnet
Domains
Generator
Solenoid
Magnetic Poles
Compass
EM Induction
Transformer
Faraday’s Law
121
What are the general properties of magnets?
 Polarized – north and south poles
 Penetrates all materials
 Attracts and repels
Demo: cow magnets, neodymium magnets, iron magnet
Bi-polar – (polarized) naturally occurring, permanent poles, north and south,
that always come in pairs. There are no magnetic monopoles – isolated north,
or isolated south pole.
Like poles __repel_
Unlike poles ___attract__
Magnetic Domains – theorized areas of magnetic materials that have a common
magnetic direction. Arrows point north.
What would happen if you broke a permanent magnet in half?
You would have two smaller magnets, each with a north and south pole – can’t
break the poles.
 Some metals have a high magnetic susceptibility:
o Iron, cobalt, nickel, tin, molybdenum, niobium, neodymium
o Each have more than 2 unpaired up electrons in their orbitals
 Electron configurations determine the magnetic susceptibility.
 More unpaired electrons = __stronger magnetic moment___
122
Magnetic Fields – a vector that relates the amount of force on a magnet or
current carrying wire (represented by magnetic flux)
Demo: magnetic field visualizer, magnaprobe
 Flux lines go from North to South
Magnetic field of the Earth:
Assign Ch. 36: 1-9
123
What is a compass? What is it used for?
A small freely rotating magnet. Detecting the presence and direction of
magnetic fields.
What happens to a compass when it is brought near a magnet?
It rotates to line up with the direction of the magnetic field.
Why does the needle deflect when the power is turned on?
There is a magnetic field that rotates around a current carrying wire.
Demos: compasses, magnet, and high current wire
Electromagnetism – a current carrying wire produces a circulating magnetic
field around the wire and its strength is proportional to the amount of
current.
 It deflects in a certain direction depending on which direction the
electrons flow.
1st Right Hand Rule – if the thumb on your right hand points in the direction
of the current, your fingers wrap in the direction of the field.
124
What happens when two wires have current passing each other in the same
direction? Remember, fields are vectors! (they have a direction)
 The net result is a field that reinforces in certain areas and reduces
in others: the wires are attracted to each other.
What happens when two wires have current passing each other in the opposite
direction? The wires repel from one another.
When combined in a series of wires, the field reinforces itself, creating an
intense magnetic field with certain characteristics:
2nd Right hand rule – If the fingers of
your right hand wrap around in the
direction of the current, then your thumb
points toward the north.
Solenoid – A coil of current carrying wire that simulates a magnet.
Demo: electromagnets
125
Iron Atom:
Has 3 unpaired electrons “circulating” around the nucleus
If an electric current produces a magnetic field, could a magnetic field push
on a current carrying wire? Yes. The magnetic fields will still push on each
other.
3rd Right hand rule – If your thumb points in the direction of the current,
with your fingers pointing the direction of the magnetic field, your palm
points in the direction of the induced force.
 Force causes the wire to move because of the current flow in the wire.
 It also works in reverse! A force moving the wire through a magnetic
field creates a current in the wire.
Electromagnetic Induction – the movement of a loop of wire perpendicular
through a magnetic field will induce a current in the loop that opposes the
wires motion through the magnetic field.
Demo: electric generator
126
What are the methods of producing an electric current
induction?( 3 basic methods)
Faraday’s Law – the intrusion of a magnetic field in
in the conductor producing a magnetic field (current)
the magnet.
1. Move a wire perpendicular through a magnetic field
using electromagnetic
a conductor will result
to oppose the motion of
– electric generator
2. Move a magnet perpendicular through a coil of wire – faraday flashlight
3. Lens’law – vary a magnetic field in a conducting coil and it will produce
a current in the coil. (electric transformer)
Demos: magnet down Al plane, magnet down Cu tube,
ring launcher(holding rings)
Assign Ch. 37: 2-4, 7-9
127
What is the power output of a light bulb when attached to the step-up
transformer? Step-down transformer?
Increased due to increased voltage, decreased due to lower voltage
 Applying the law of conservation of energy:
o Powerin = Powerout
Calculate the number of turns on the output coil of the step-up transformer.
The primary coil has 300 turns, 120V, and 15A.
Predict the ideal voltage and current output from the following step-up power
transformer:
100 turns 400 turns
Input is 120V, 20A
V = 480 V, 5 A
Assignment Ch. 37:
11-15, 40, 43-46, 57, 59
128
You may work with a lab partner in this assignment. First, you will research
a personal interest as it applies to physics (e.g., the physics of tennis,
the physics of swimming). Your presentation subject must be approved by your
instructor. After your research, you will prepare and present a presentation
on your subject to the class.
Your research and presentation will be worth 100 pts. Your grade will be
determined by the following criteria: 1. Meeting all of the basic
requirements, 2. Having correct information and research, and 3. The overall
appearance and professional delivery of the presentation (including
preparedness, neatness, and professionalism)
You must have at least two different research sources (they may not be from a
textbook and only one of them must be an internet source). The sources must
be recent, within the last 10 years. You must write your sources on a
bibliography page in MLA format to be handed in. The presentation must be at
least 4 min. long and use 2 different visuals. (e.g., poster and powerpoint,
video and powerpoint, demonstration and model)Each lab partner must have
equal time in giving the presentation.
You will be given four class periods to work on your projects. They will be
spread out throughout the end of the semester. These are graded work periods
– so keep busy! – no personal discussions!
129
Be sure you understand the concepts and the terms below for you final exam. Review all of
the class examples, homework problems, notes, and worksheets. Also be sure you understand
all math principles and problems for each chapter. This is not an exhaustive list of what
you should know but is a starting point. You may write down other examples or information
not on this review for your use on the exam. The back of these pages are blank for extra
space.
 Write down key terms with their definitions.
 Write down the equations used in the Chapter.
Speed –
Instantaneous Speed –
Average Speed –
Velocity –
What is the difference between speed and velocity?
What is a vector?
Acceleration –
What are the 3 things you can do to accelerate your car on level ground?
What is freefall? What is ignored?
What are the two main freefall equations? How are they used?
A ball is thrown straight up. What is it’s velocity at the top of its
trajectory?
A ball is thrown straight up with a velocity of 20 m/s. How high will it go?
130
Components –
Projectile –
What is ignored in projectile motion?
If a ball is thrown horizontally and another ball is dropped from the same
height, which one hits the ground first? Why?
What angle gives maximum range?
Which pairs of angles give the same range?
A cannon fires a projectile with a horizontal velocity of 100 m/s from a
building 45 m high. How far from the base of the building will the ball land?
Newton’s 1st law of motion –
What is Newton’s definition of mass?
What is the difference between mass, weight , and volume?
Equilibrium –
Newton’s 2nd law of motion –
Friction –
Air resistance –
Pressure –
How can you figure out how much your car weighs using pressure?
Terminal Velocity –
131
Newton’s 3rd Law of motion –
Interaction pair –
Action: Jill pushes off of Jack.
Reaction:
Jack and Jill are both on frictionless carts. Jill has a mass of 35 kg, and
Jack has a mass of 50 kg. Both are at rest. Jill pushes on Jack with a force
of 30 N.
a. What force will Jack have on Jill?
b. What will be Jill’s acceleration?
c. What will be Jack’s acceleration?
Momentum –
Impulse –
What are the equations for both?
What happens when you increase impact time?
What do airbags due to impact time?
Conservation of Momentum –
Elastic Collisions –
Inelastic Collisions –
132
What is the origin of the Electromagnetic Force?
Where do we get charges?
Identify the atomic particles that make up a typical atom.
Identify the properties of charges.
Law of Conservation of Charge –
How do we get charged objects?
Identify and explain the 3 methods of charging.
Coulomb’s Law –
What physical difference makes a material a conductor or an insulator?
What creates an electric current?
Electric Current –
Voltage –
Electric Resisitance –
Ohm’s Law –
What is the difference between AC current and DC current?
Identify a source of each of the previous?
Where do the electrons for electric current come from?
Electric Power –
What is a kilowatt-hour?
133
Electric Circuit Series Circuit - Explain its properties.
Draw a schematic diagram of a series circuit with three 30  resistors
connected to a 10 V battery.
Calculate the total resistance of the previous circuit, the current out of
the battery, and the volts used by each resistor.
Parallel Circuit - Explain its properties.
Draw a schematic diagram of a parallel circuit with three 30  resistors
connected to a 10 V battery.
Calculate the total resistance of the previous circuit, the current out of
the battery, and the current used by each resistor.
Compound circuit Draw a schematic diagram of a compound circuit with four 30  resistors
connected to a 10 V battery.
Calculate the total resistance of the previous circuit, and the current out
of the battery.
134