Transcript Slide 1

Make cut out bus or train with the
windows cut out, 2 or 3 cut out people, a
beautiful background (forest, city, etc),
and your phone.
1. Place your cut out bus on the background and place your people
on the bus. Move the people back and forth at the same speed
within the bus. Keep the viewing frame of your phone locked on
(moving with) the cut out people. According to what you see in
your viewing frame, are the people moving?
2. Move the people and the bus back and forth while keeping your
viewing screen locked on the bus and having the bus fill up your
viewing screen. How are things moving?
3. Now keep your viewing frame locked on the background and
slowly zoom out. How are things moving?
Relative Motion 1
A blue car moves along a street with two passengers. One sits in the
front passenger seat of the car and the other passenger sits in the
back seat. A red car moves in the same direction and is passing the
blue car. A green car moving faster than the blue car, is directly
behind the blue car. There is a sidewalk along the road the cars are
traveling and a pedestrian is standing on the sidewalk.
Describe the movement of the front passenger in the
blue car as seen by each of the following observers:
1. The person sitting in the backseat of the blue
car.
2. The pedestrian standing on the sidewalk as the
blue car passes.
3. The driver of the red car moving in the same
direction and passing the blue car.
4. A passenger in the green car.
Relative Motion 2
A blue car moves along a street with two passengers. One sits in the
front passenger seat of the car and the other passenger sits in the
back seat. A red car moves in the same direction and is passing the
blue car. A green car moving faster than the blue car, is directly
behind the blue car. There is a sidewalk along the road the cars are
traveling and a pedestrian is standing on the sidewalk.
1. Imagine you are the backseat passenger in the blue
car, how would you observe the other four observers?
Explain.
2. Imagine you are the pedestrian in the street, how
would you observe the other four observers? Explain.
3. Based on your answers above, explain what it
means when someone says an object is “moving”.
4. Consider the phrase “motion is relative”. Use your
idea of what it means to move to explain the meaning
of this statement.
Relative Motion 3
Tom is on a train moving at 10m/s
when he drops his phone from his
hand to the floor of the train 1.5m
away. If Jon is standing on the ground
outside the train 7m from Tom when
he begins to drop his phone, how far
away from Jon will the phone land?
Relative Motion 4
Erin, Chris, and Dhruv are on their way to a vacation. They are racing
to the train from three separate locations Erin makes it to the train
on time and sits in the back of the train. Dhruv barely makes it there
on time and the train pulls out of the station at -20m/s. Dhruv walks
to the back of the train to meet Erin at 3m/s. Chris does not make it
to the train. He stands and watches as the train pulls away. What are
the velocities of the following?
a. Erin relative to Chris
b. Dhruv relative to Chris
c. Dhruv relative to Erin
d. Chris relative to Erin
e. Erin relative to Dhruv
f. Chris relative to Dhruv
Relative Motion 5
•
•
•
•
•
•
•
A toy car moves 2m every 2s
for 10s. What kind of a
representation is this? Create
as many representations of this
as possible.
Verbal
Picture
Index
Table
Function/Equation
Plot Graph
Motion Diagram
Velocity 6
Smashy Smashy Car Crashy
Where will 2 cars collide?
Velocity 7
Curiosity
Observe Data then Hypothesize from Data
Patterns
Observation Experiement
Method
• Materials
• Timer
• Meter Sticks
• Sand Bags
• Blue & Red Car
• Procedure
• Error/Uncertainty
Results
• Data
Reason a Hypothesis from Patterns in Data
Velocity 8
Represent Car Motion Hypothesis
Using all of the Following
• Verbal Representations…
•
•
•
•
•
•
Picture
Index
Table
Function/Equation
Plot Graph
Motion Diagram
Some of these representations overlap
(e.g. you need an index and equations in your motion diagram)
Velocity 9
Skepticism
Predict to Test your Hypothesis
Predict the outcome of a Testing Experiment assuming your
Hypothesis is correct.
Perform the Testing Experiment then compare the
actual outcome to your prediction. Your test is an
experiment and must include…
Testing Experiement
Predict
Method
• Materials
• Procedure
• Error/Uncertainty
Results
• Data
• Compare Predicted to Actual Outcome, Revise if Necessary
Velocity 10
Represent Car Motion Prediction
Using all of the Following
• Verbal Representations…
•
•
•
•
•
•
Picture
Index
Table
Function/Equation
Plot Graph
Motion Diagram
Some of these representations overlap
(e.g. you need an index and equations in your motion diagram)
Velocity 11
Four friends
represented
the motion of
the same car in
different ways.
Which would
best represent
the motion of
the car as a
function of
time?
Draw the one
you think is
best and label
why.
Velocity 12
Mayes and Patel are at the
boardwalk. They are riding bumper
cars and heading straight towards
each other. If they start 10 m
apart, M is going 1m/s, and P is
going 2 m/s, where will they meet?
Answer with a motion diagram and
plot graph.
Velocity 13
Represent
this data
with motion
diagrams,
graphs, and
equations.
Predict
where they
will meet.
How did
you
predict?
Shiv
Position (x)
Time (t)
1m
0s
2.5m
1s
4m
2s
5.5m
3s
Megha
Position (x)
Time (t)
10m
0s
8m
1s
6m
2s
4m
3s
Velocity 14
0s
Kevin sees a spider crawl up Nishi’s leg and
measures position each second.
Nishi measures her hand’s position each second to squash the
bug. When and where does she squash the bug? Use MD’s, 0s
and plots.
What can you say about the motion of Nishi’s hand?
Acceleration 15
Hypothesize the motion of a ball
if you set it in motion then let it
roll to a stop.
Materials: Meter sticks, balls,
sand bags, books, timers
Acceleration 16
Nainil measured a bug scampering away.
Create a motion diagram.
Plot these points on a position vs. time graph.
Find the change in velocity between each dot
st dot to the 11th.
from the
the
1
Δt = 1s
0s
Acceleration 17
Cheryl and Wendy are exercising in Roosevelt
Park. When you start observing them, Wendy is
50 meters ahead of Cheryl. Wendy is jogging at a
speed of 5 mph and Cheryl is running at a speed
of 7 mph in the same direction. Dan is riding a
bike at 21 mph in the opposite direction of
Wendy’s velocity. He is 12 meters ahead of
Wendy in the opposite direction of Cheryl’s start
point when you start observing them. How far will
Dan be from Cheryl and Wendy when Cheryl
catches up to Wendy?
638m
Acceleration 18
We have learned that V = Δx/Δt
Using this, what is acceleration?
Use words and equations for your
answer.
Acceleration 19
Tim rolled me down a hill.
Plot-graph this data of my position at a clockreading.
What is each ΔV and acceleration? Plot velocity versus time.
Position
Time
1m
1s
4m
2s
9m
3s
16m
4s
25m
5s
36m
6s
49m
7s
Acceleration 20
Dennis throws a tennis ball
away from Earth with an
initial velocity of 100 m/s
up.
Make a position vs. time
graph and V vs. t graph.
What is the acceleration?
How high does it go
(distance)? How far away is
it from where it started
(displacement)?
Time (s) Position (m)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
0
95.1
180.4
255.9
321.6
377.5
423.6
459.9
486.4
503.1
510
507.1
494.4
471.9
439.6
397.5
345.6
283.9
212.4
131.1
40
Acceleration 21
An object has an initial vertical
velocity of Vi = 10m/s. Create a
problem with rubric which uses
this as the answer.
Acceleration 22
How do we calculate
acceleration?
How could we find Vf from this if
we know all other physical
quantities?
Kinematic Equations 23

v vf v
i
a 

t t2t1
vf vi at
Kinematic Equations 24
Create a mathematical procedure
for finding the area under the
graph.
Vf
Vi
Kinematic Equations 25
By breaking the area under the
curve into a rectangle (area=vit)
and triangle (area=½(vf – vi)t) then
adding them together we get
1
d
isplacemen
t (
v

v
)

t
f
i
2
Kinematic Equations 26
Derive the following kinematic equations
below from three you have derived.
1 2
dvit at
2
vf v 2ad
2
2
i
Kinematic Equations 27
Substitute
vf vi at
into
1
d (vf v
)

t
i
2
to get
1 2
dv
t a

t
i
2
Kinematic Equations 28

v vf v
i
Multiply a 

t t2t1
by
to get
1
d (vf v
)

t
i
2
vf v 2ad
2
2
i
Kinematic Equations 29
Draw a motion diagram for an
apple falling from rest for 4
seconds. What will the Vf of the
apple be?
Kinematic Equations 30
Make a story for each graph both
verbally and mathematically.
Kinematic Equations 31
Create a problem with a rubric
whose answer is a = -4.6m/s2.
Kinematic Equations 32
The Flash’s motion is described in
equations below. Use as many other
representations as possible to describe
this motion.
Jess and Matt are walking down a hallway. Matt is carrying
a box of Mentos™ and Jess is carrying a crate of Coke™.
Will they be covered in explosive grossness?
2D Kinematic Equations 34
2
2m/s
An airplane accelerates at
due East from a speed of 700m/s
for 50s. How fast will the plane be
going if there is also a 100m/s
o
wind blowing at 33 North of
East?
2D Kinematic Equations 35
Cheryl pegs Mr. Mayes with a snowball. The
snowball leaves Cheryl’s hand with a velocity
of 10 m/s at an angle of 30o away from the
ground (Earth).
Projectiles and 2D Motion 36
The First Half of the Trajectory
Y or Vertical Dimension
• After the balloon leaves the launcher, it travels
upward in the path of a parabolic arc until
gravity decelerates it’s vertical, upward
motion to a stop.
Projectiles and 2D Motion 37
Second Half of the Trajectory
Y or Vertical Dimension
• Gravity then accelerates the projectile
downward from the top of this arc.
Projectiles and 2D Motion 38
Hang Time (Δt)
• Using the kinematic equations we need to
calculate how much time it takes for the Y
velocity from the sling to decelerate to zero at
the top of the first half of the projectile’s
trajectory.
• This gives us half of our “hang time” (Δt1/2) or
half the time the projectile spends in the air.
• Multiply by 2 to get the total hang time and
use the kinematic equations to find the
distance the projectile travels in it’s trajectory.
Projectiles and 2D Motion 39
The Whole Trajectory
X or Horizontal Dimension
• With no forces acting in the
horizontal or X dimension
after the initial projection,
what does the X velocity do
throughout flight?
Projectiles and 2D Motion 40
The Whole Trajectory
X or Horizontal Dimension
• If we use trigonometry on the initial velocity
out of the sling, we get the constant velocity
of the balloon in the X direction throughout
flight.
• We also have the hang time.
• We have a rate (V) and a time interval (Δt), so
we are able to get the total displacement the
balloon travels from d = VΔt
Projectiles and 2D Motion 41
Patel Pegs Mayes
Cheryl pegs Mr. Mayes with a snowball. The
snowball leaves Cheryl’s hand with a velocity
of 10 m/s at an angle of 30o away from the
ground (Earth). How far away from Cheryl is
Mr. Mayes standing?
Projectiles and 2D Motion 42
Projectile Physics
Hypothesize
Design an experiment to hypothesize what the
initial velocity of a marble being shot out of
your launcher is.
***!!!Reminder!!!***
Experiments need methods, data, assumptions and
error/uncertainty.
Analysis of the data is looking for patterns and your
conclusion is your hypothesis from these patterns.
Projectiles and 2D Motion 43
Projectile Physics
Predict
Now we test our hypothesis by
predicting how far our launcher will
launch if firing at a 30o angle.
Projectiles and 2D Motion 44
Daredevil Canyon Jump
Aditi ‘The Awesomizer’ tries to jump a canyon of width
80m. To do so, she drives her motorcycle up a ramp. The
ramp is at an angle of 17.5 degrees up from the ground.
What minimum Vi is necessary to successfully jump the
canyon? Express your answer with JUST variables first, then
put quantities in.
Not to be outdone, Gunica ‘The Brawler’ Bhatia attempts
to jump an even larger part of the canyon. She measures
the canyon and calculates that her initial speed must be
26.7 m/s at an angle of 17.5 degrees to just barely clear the
larger part of the canyon. What is the width of the canyon
here? Express your answer with JUST variables first, then
put quantities in. Projectiles and 2D Motion 45
Let’s make our own projectile problems.
Your group will have to create three problems.
These problems have to solve for:
1. Θ
2. ΔX
3. Vi
Your problems must have answers and a rubric.
Projectiles and 2D Motion 46
Lets consider a ball being launched
across a flat field where the initial and
final heights of the ball are the same.
Derive an expression for the horizontal
distance travelled solely in terms of the
initial velocity, acceleration due to
gravity, and the angle at which it is fired.
***Hints!!!***
1. How could we make our reference frame as easy as possible for ourselves?
2. What kinematics equation could we use which requires the least assumptions
and is the most comprehensive?
3. How do we link the horizontal and vertical components?
4. How could we simplify?
Projectiles and 2D Motion: Range Equation 47
What similar action is involved in
all of the following activities?
• You pedal a bicycle to start moving then apply the
brakes to make it stop moving.
• You hit the accelerator (gas pedal) to make a car
speed up after the light turns green, then you hit the
brakes to stop for the next red light.
• A spring pushes a marble to accelerate it out of your
launcher.
• You push a baseball to speed it up for a throw. A
friend then pushes on the ball after it enters her
glove to slow it down and catch it.
Newton’s 1st and 2nd Law 48
• To hypothesize anything you must find patterns in
data.
• To obtain the data you must conduct observation
experiments
• Like all experiments, this must have methods,
analysis of assumptions, and analysis of
error/uncertainty.
Hypothesis…
• Must be based on the pattern you devise from all
data from all observation experiments.
• Must use multiple representations and usually as
variables in an equation (proportional relationship
between physical quantities).
Science Method Recap 49
Hypothesize how pushes and pulls
change motion of different masses.
Materials (every single material MUST be used… this means you
should design multiple experiments)
• Mass scale
• Your muscles (you lift things up and put them down…
grarghhh!!!!!)
• Big ball (bowling/medicine) *1kg=2.2046lbs on Earth*
• Medium ball (tennis/baseball)
• Small ball (marble)
• Stopwatch
• Meter stick
Newton’s 1st and 2nd Law 50
Make a diagram with force vectors
for a box sitting stationary on the
ground.
Force Diagrams 51
Make a force diagram for a box
being pushed on a rough surface
but remaining stationary.
Force Diagrams 52
Make a diagram for a box being
pushed along a rough floor at a
constant velocity.
Force Diagrams 53
Draw motion and force diagrams for the
following:
-You are driving in the school parking
lot when a man in a gorilla suit sprints
toward your car. You hit the gas to get
away from this weirdo.
-A very large water balloon is projected
vertically near the school on a day when
the air is thick but there is no wind.
-A raw egg is projected across the
parking lot at Mayes’ car.
Force Diagrams 54
A rectangular sheet of material has a width of 3m and a
length of 4m and is held stationary to look taller rather
than wider. A 3N pull is exerted in the upper left corner
to the left and a 4N pull is exerted in the lower right
corner in the downward direction. What is the
magnitude of the force exerted from the person in the
upper right corner at what angle relative to the top
side of the sheet? Explain all answers, justify
assumptions, and use multiple representations.
Force Diagrams 55
Hypothesize how two things push
or pull on each other.
Materials:
2 bathroom scales
2 spring scales
2 scooters
Newton’s 3rd Law 56
Jackie exerts a 9.8 N force
upward on a 1 kg snowball
on Earth. Draw this situation
focusing on the snowball.
Newton’s 3rd Law 57
Jackie exerts a 9.8 N force
upward on a 1 kg snowball
on Earth. Draw this situation
focusing on Jackie’s hand.
Newton’s 3rd Law 58
Make a chart of
representations for
Newton’s Laws which
includes Math, Words,
Diagram, and Example.
Newton’s Laws 59
Make a force diagram for 3
stationary, stacked boxes. The
most massive box is on the bottom
and the least is on the top. Use a
separate diagram for each box as
the system and one for all three as
the system.
Force Diagram Problem 60
Make a diagram for 2 boxes (top
3kg, bottom 5 kg) stacked
vertically and being pushed
horizontally along a rough floor
at a constant velocity.
Force Diagram Problem 61
o
60
A 2000 kg car sits on a
hill in
San Francisco. What is
Fstaticfriction on car?
Force Diagram Problem 62
Three boxes (top 1kg, middle 3kg,
bottom 5 kg) are stacked vertically
and being accelerated horizontally
along the floor at 5 m/s2. The force
of kinetic friction exerted from the
ground on the bottom box is 500N.
What are all of the forces exerted
on each of these boxes as shown
by a diagram?
Force Diagram Problem 63
Two masses are vertically hanging on either side
of a small frictionless pulley (this is called an
Atwood machine). One of the objects has three
kilograms of mass.
What is the mass of the other object if it is
stationary?
What is the mass of the other object if it is
moving at a constant speed downward?
What is the mass of the other object if it is
accelerating down at 2m/s2?
What is the mass of the other object if it is
accelerating up at 2m/s2?
Atwood Machine 64
A 5kg mass and a 10kg mass are connected by a
10m long string. Afterward, they are hung over
a small, frictionless pulley with the 10kg block
touching the pulley and the 5kg block hanging
low. It they are released, how long would it take
for any subsequent action to occur?
Atwood Machine 65
Predict to test Newton’s Laws
Materials: phet.colorado.edu ‘Forces and Motion’
Newton’s Laws 66
Hypothesize how friction operates
on a subatomic scale.
Materials: phet.colorado.edu ‘Friction’
Friction Force 67
Hypothesize the relationship
between the friction force of
the floor on your shoe and the
amount of normal force
exerted by the floor on your
shoe.
Friction Force 68
If a 3500kg object
rests on a hill with a
o
30 slope up from
horizontal. What is
µstatic?
Friction Force Problem 69
If a 3500kg object
o
slides on a 37 slope
and is µkinetic = 0.004,
describe this object’s
motion?
Friction Force 70
Hypothesize the relationship
between the force used to
stretch a spring and the
distance it is stretched.
Spring Force 71
Spring, Tension, and Friction Force 72
4 kg
µkinetic = 0.02
alarge = ?
Assumptions?
12 kg
Spring, Tension, and Friction Force 73
1.
2.
3.
4.
5.
6.
Hypothesize using the
following materials:
String
Pulleys
Masses
Balloons (Helium and Atmosphere)
Springs
Measuring Devices
Scientific Method for Forces 74
Hypothesize a quantitative model
for the force which moves objects
in circles.
Materials: ball on a string
Central Force 75
central force
Meghana spins a ball around her head on a
string. The velocity of the ball is 5 m/s, the ball
has 1.3 kg of mass, and the radius of the circle
she is spinning is 2m. Draw a diagram of this
situation with all necessary physical quantities
including the central force and acceleration.
Then draw this same situation for:
1) Doubled velocity
2) Halved radius
3) A ball 4 times larger
***Make sure to create multiple
representations and list assumptions.***
Central Force 77
It takes 34s for Vidya to do a full
circle doughnut in a snowy parking
lot with his car. The lines in the
snow from the car are 10m wide.
What is the circular acceleration of
car while it is doughnuting.
Central Force 78
Mr. Mayes is swinging a bucket of
water above his head. The bucket
and the water is 10kg. Mayes’ total
wingspan is 78 inches and it takes
him 2 seconds to spin the bucket.
Create force diagrams for the top
and the bottom of the motion.
Central Force 79
Indiana Jones has a 3kg mass at
the end of his 3m long whip to
fight the UngaBunga tribe of
cannibals. What does he have to
do with his whip to stun them with
100 N of force? If he has to stun
the tribal chief which takes 9 times
the force, what will he have to do?
Central Force 80
Hypothesize the relationship
between the quantities which
determine the gravitational force
between two objects.
Materials: phet.colorado.edu
‘Gravity Force Lab’
Gravitational Force 81
Gravitational Force 82
Draw a diagram of the force
exerted on objects with mass
(system masses) by a massive
central object (source mass).
THEN ERASE THE TEST OR SYSTEM
MASSES (not the center source
mass)
Gravitational Force Field 83
What is the gravitational force
between Earth and Sol (the sun)?
3.5 x 1022 N
Electric Force 84
Make a Venn diagram
comparing Motion
(Kinematics) and
Forces (Dynamics).
1 D Momentum 85
Consider the following:
1. A softball is pitched underhand.
2. The driver of an Abrams tank hits the gas.
If they both have the same final velocity and acceleration to get to
that final velocity, what is different about these two scenarios?
How would the force and motion diagrams for these two
compare? How could we account for this?
1 D Momentum 86
You have bowling balls, pool balls,
tennis balls, and golf balls. Create
experiments to observe what
happens during various collisions.
Invent a physical quantity to
communicate these situations.
Keep in mind this physical quantity
must combine the factors unique
to motion and forces respectively.
1 D Momentum 87
Hypothesize the aspects of this new
physical quantity (momentum).
Design experiments using:
1. pool ball and a golf ball
2. phet.colorado.edu ‘collision lab’
Make sure to identify the
independent, dependent, controlled,
and confounding variables. Include
assumptions and error.
1 D Momentum 88
Summary of Momentum
• P=mV units are kg(m/s)
• Impulse changes momentum J=mΔV=FΔt
• Momentum can be transferred from one
object to another.
• Momentum is conserved if there is no impulse
(outside force exerted in a change in time)
exerted on the system ΣPi + J = ΣPf
• Collisions can be described as inelastic (sticky)
or elastic (bouncy)
• Momentum is described with diagrams,
1 D Momentum 89
math(s), and bar charts
Create bar graphs to chronicle the
following scenario.
• You have no money in your pocket, $60 in your ATM account, and
a gift card with $20 on it. You withdraw $20 cash from the ATM.
• Next, you buy a lemons and a pitcher for $10 cash at Jones
Grocery. (The initial state for this process is the same as the final
state of the previous process.)
• After returning from the grocery store, you make lemonade and
manage to sell enough to make $10.
• When you are finished selling lemonade, you spend $20 cash to
put gas in your car so you can drive to Target.
• At Target, you purchase the new Super Mario Brothers game for
Wii for $50. You empty out your gift card and use your ATM card to
pay for the rest.
Conservation of Momentum Bar Graphs 90
A 70.0 kg man and his 40.0 kg daughter
on skates stand stationary together on
a frozen lake. If they push apart and
the father has a velocity of 0.50 m/s
eastward, what is the velocity of the
daughter? (neglect friction) Include a
momentum bar graph and other
necessary representations.
Momentum 91
2
10
The velocity of a 6.00 x
kg
elephant is changed from 10.0 m/s
to 44.0 m/s in 68.0 s by a constant
force from a truck which is shipping
it. What is the impulse on, force
exerted on, and acceleration of this
object? Do this in as many ways as
you can think of.
Momentum 92
Before
5 kg
2m/s
3 kg
1. Analyze this
scenario in terms
of momentum.
2. Analyze this
scenario in terms
of forces and
motion.
After
0.5m/s
5 kg
3 kg
?m/s
Momentum 93
Aditi and Cheryl are competing over who can make a ball
stay airborne for the longest amount of time. The
displacement through which Aditi accelerates the ball out
of her hand is 0.2m, while Cheryl accelerates the ball out
of her hand during the throw in exactly 2s. Aditi throws
the ball with an initial speed of 40 m/s and Cheryl throws
her ball so the total vertical path covered is 164m. When
the balls hit the ground they both have an inelastic
collision with the ground and an impulse of 75 kg m/s is
exerted on the balls by the ground. Whose ball stays in
the air for the longest amount of time?
Momentum Problem 94
We created momentum as a replacement for using both
motion and forces together… but does momentum always
make our physics easier? Does it always work?
Create testing experiments to test the hypothesis that
momentum
P=mV
ΣPi + J = ΣPf
is a viable physical quantity which makes doing physics
easier.
You are trying to DISPROVE this. Nothing is proven…
ever… nothing… nada… zilch… goose egg.
Work 95
Suggested Materials
•
•
•
•
Create testing experiments to
test the hypothesis that
momentum
P=mV
ΣPi + J = ΣPf
is a viable physical quantity
which makes doing physics
easier.
Chalk and brick
String with sandbag
Wind up Toys
Whatever your creative minds can come up
with (within the bounds of reason and
politeness)
Work 96
For cases wherein
momentum is no longer
a viable physical quantity
to use, invent a new
physical quantity to
analyze these
phenomena.
Materials: Chalk and massive
object
Work 97
What is fundamentally different
between the physical quantity you
invented and momentum?
What about your new physical
quantity allows makes it easier to
analyze the situations momentum
couldn’t?
Work 98
A man carries a 5kg bowling ball up
a 2m ladder then walks another
5m on the roof while carrying it.
How much total work is done on
the bowling ball? Make sure to
make both a force and motion
diagram for each part.
Work 99
What is different and similar between the
everyday idea of work and how we describe it in
physics?
Work 100
Hypothesize where work goes
when you do work to lift a tennis
ball. Derive a mathematical
expression for the amount of
‘stored work’ whenever work is
done lifting something.
Stored Work 101
Hypothesize where work goes
when you do work to move an
object. Derive a mathematical
expression for the amount of
‘stored work’ whenever work is
done to move something. Use the
equation for work you discovered
and kinematic equations.
Stored Work 102
Hypothesize where work goes
when you do work to stretch a
spring. Make a spring force vs.
displacement graph. Derive a
mathematical expression for the
amount of ‘stored work’ whenever
work is done stretching a spring.
Stored Work 103
Work gets stored as Energy
• Work done stretching a rubber band or
compressing & stretching a spring is stored as
elastic potential energy
» EPE=0.5kΔx2
• Work done lifting an object such as a ball is
stored as gravitational potential energy
» GPE=magΔx
• Work done making an object move is stored as
kinetic energy
Energy 104
» KE=0.5mV2
You stretch a slingshot 1m which
has a spring constant of 1000N/m.
You place a 1kg ball in the
slingshot. Ignore air resistance. If
you release it vertically, how high
will it go? What will the final
velocity of the ball be?
Energy 105
Design a virtual observation
experiment to discover an
explanation of friction in terms of
work and energy.
Materials: PHET Friction
Friction with Energy 106
Mayes is driving home from a full night
of coming up with awesome things to
do in class. My car masses 1,633 kg
and is moving at 20.0 m/s. There is a
red light 40m ahead of me. The
coefficient of kinetic friction between
the road and my car tires is 0.04. Will I
run the red light or stop in time? Do it
with energy, momentum, and forces.
You Choose What To Use 107
You stretch a slingshot 1m which
has a spring constant of 1000N/m.
You place a 1kg ball in the
slingshot. Air resistance is 2N for
the entire flight. If you release it
vertically, how high will it go?
What will the final velocity of the
ball be?
Energy 108
You stretch a slingshot 1m which has a spring
constant of 1000N/m. You place a 1kg ball in
the slingshot. Air resistance is 2N for the entire
flight.
Analyze this situation with a bar chart assuming
the system is:
1. The ball.
2. The ball and Earth.
3. The ball and the slingshot.
4. The ball, the slingshot, and Earth.
5. The ball, the slingshot, Earth, and the
surrounding air.
Energy 109
Design and perform virtual testing
experiments to test the following
hypotheses separately on Energy
Skate Park PHET:
Work and Energy is Conserved
KE=1/2mV2
GPE=mgΔx
I suggest you turn on and use all tools available to you in
the simulation. FRICTION MUST BE ‘ON’ WITH A
COEFFICIENT OF FRICTION BETWEEN ‘NONE’ AND ‘LOTS’.
Energy 110
Something happened one day and it was
described by Matt in the following way.
½
2
kx +
Wdrag=
2
½mV
+ mgy
Create a scenario for what this could
possibly describe with a diagram, a
bar chart, and words.
Energy 111
Hypothesize the
maximum velocity
of a bouncy toy
using only
measuring tape.
Energy & Momentum 112
Hypothesize the
spring constant of
your springy toy
using only
measuring tape and
a mass scale.
Energy & Momentum 113
Hypothesize the work
done in each single
wind of a wind-up toy
using measuring tape
and a spring scale.
Energy & Momentum 114
A Newton’s cradle consists of a series of metal
spheres hung in a row. One is raised then falls as
a pendulum and strikes the row of other spheres.
Thus, a sphere at the opposite end bounces up. It
is possible for one sphere to fall on one end and
have a sphere raise on the other side. Likewise, it
is possible for two spheres to fall, strike the row,
and two spheres bounce up at the other end. Is it
possible for one sphere to strike the end and
have two sphere bounce up on the other? Is it
possible for two spheres to strike one end and
have one bounce up on the other?
Energy & Momentum Conservation 115
Hypothesize how much energy is had
by two charges near each other.
Hypothesize how much energy is had
by two masses near each other.
Materials:
•Your expression for gravitational force,
electric force, and mechanical work.
•Phet – Gravity Force Lab
Gravitational Potential and Electric Potential Energy 116
What is similar and different about
these situations? Compare with a
Venn diagram. Then, come up with
a physical quantity (index) to
compare the two scenarios.
A flexed muscle quickly pushes a
marble with 10N of force over 1m.
A light breeze pushes a marble
slowly with 10N over 1m. Power 117
What is different and similar
between the everyday idea of
power and how we describe it in
physics?
Power 118
A 5kg box slides to a halt from 5m/s over a
distance of 20m. What is the coefficient of
kinetic friction between the ground and the
box? How much work is done due to friction
on the box? 62.5 J How much power is
exerted on the box?
m = 5kg
Vf = 0m/s
V0 = 5m/s
ΔX = 20m
Power 119
You have various ramps with the
same height but each have
different paths. If we roll marbles
down each of these ramps and
release them at the same time,
predict which ramp will take the
least amount of time for the
marble to travel from the top to
the bottom.
Power
120
You have developed superpowers overnight. You can now
stretch your arms to reach ridiculous heights. You decide to
become a hero and on your way home from school, you do
the following heroic acts. Determine how much power you
exert while lifting the following objects. Draw a picture of the
initial and final states.
a) You rescue a 0.05kg bird from the sidewalk and place it
back in its nest, 5.2m up in a tree, in 1.0s.
b) You lift a 6kg bag of Oreos 3.0m up to your tree house in
6.0s for your slumber party with your friends (you have
been saving up for all the Oreos).
c) You lift a 10.4kg bag of rice 2.6m to the top of the pantry
for your mom in 2.3s.
d) Your 70-kg sister twisted her ankle so you lift her from
the foyer to the second floor 4.0m straight up in 10.0s.
Power 121
Exercise Power House
You’ve got the POWER!
Hypothesize the amount of power
required to run up a single stair.
BE VERY VERY CAREFUL!
Power 122
Exercise Power House
Now that we know the power
delivered by legs while climbing stairs,
create a proposal for a Stairmaster
which will power all the lights in a
house (ignore the kitchen).
Many assumptions must be made to
do this.
Power 123
Bree and Yash are debating the best way to
put bowling balls away on the lab table after
an experiment. Bree says it is easier to use a
ramp to roll the bowling ball back to the lab
table she got it from. Yash says it is easier to
simply lift the ball and put it on the lab
table.
Who is right?
Design experiments to gather evidence to
validate your claim.
Simple Machines 124
Tim claims that he made a
machine out of a simple pulley
and a string which will reduce
the amount of work done to lift a
mass to a specific height. Create
a testing experiment with a
prediction to test this
hypothesis.
Simple Machines 125
Do research and
design your own
simple machine which
does something to
improve your life!
Simple Machines 126
Misconceptions
Motion is absolute. Everyone will agree on the motion of an object.
A force is required for motion. Objects eventually stop with no forces exerted on them.
Motion is in the direction of the net force.
For every action there is an equal and opposite reaction and the sum of the 'actions' is 0.
Nothing is conserved if there is impulse/work.
A large truck collides with a compact car. The truck exerts a greater force and conveys a
greater momentum to the car.
A ball is projected up by a spring and there is no air resistance. If the ball is the system
no work is done, energy just transfers.
Objects move in a circle because of the tangential velocity due to the centripetal force.
Semantics of Gravity/Electricity
Misconceptions 127
Concept/Skill
from which
you must
create...
Educational
Scientific
Problem with rubric Experiment to
and solution (make it fun investigate something
or funny).
cool.
Engineering
Design which will in
some way make life
easier.
Game 128