Monday,
March 10, 2014
H Physics
Warm Up
.
Building to Standard: 2a: Students
know how to calculate kinetic energy
by using the formula E=1/2 mv2
Objective: SWBAT finish the Kinetic
Energy Lab
Describe the transfer of energy as
the truck goes down the hill.
Agenda
1. Warm Up
2. Turn in Last Weeks Homework
3. Finish Kinetic Energy Lab
Homework
E#5
Tuesday,
March 11, 2014
H Physics
Standards: Building to Standard: 2a:
Students know how to calculate kinetic
energy by using the formula E=1/2 mv2
Warm Up
A crane lifts up a box 100 m
using a 10,000 N force. How
much work is done? How
much potential energy does
the box gain?
Objective: SWBAT solve conservation of
energy problems.
Agenda
1. Warm Up
2. Conservation of Energy
Practice
Homework
P.2 E#5 P.4 E#6
Wednesday,
March 12th, 2014
H Physics
Standards: Students know how to
calculate kinetic energy by using the
formula E=1/2 mv2
Warm Up
A 2kg ball drops from
10,000 m in the air. What
is the ball’s potential and
kinetic energy when it is
2000 m in the air?
Objective: SWBAT understand how to
measure the kinetic energy of a moving
object.
Agenda:
1. Warm Up
2. Review HW
3. Motion Lab
Homework
E#6 P.2
Thursday,
March 13, 2014
H Physics
Standards: Students know how to
calculate kinetic energy by using the
formula E=1/2 mv2
Objective: SWBAT understand how to
measure the kinetic energy of a moving
object.
Agenda
1. Warm Up
2. Review HW
3. Continue Energy of Motion
Lab
Warm Up
Which person do you think
will be moving faster at the
bottom of the ramp? Explain
why using physics concepts
like energy.
Homework
P.4 EH#7
Energy Quiz – Conservation
of Energy (like the diving
board homework problem)
Friday,
March 14, 2014
H Physics
Standards: Students know how to
calculate kinetic energy by using the
formula E=1/2 mv2
Warm Up
Find the kinetic energy of a
0.5 kg marble rolling down a
ramp if the marble has a
speed of 2.5 m/s at the
bottom of the ramp.
Objective: SWBAT score 80% on their
quiz
Agenda:
1. Warm Up
2. Check HW
3. Conservation of Energy Quiz
Homework
E#8 Energy Review
Symbols, units and equations Study Guide
Equations:
Energy & Momentum
p=mv
Symbol
Units
t,T
s
v
m/s
a
m/s2
F
kgm/s2 or N
Δx, Δy, r, d
m
m
kg
p, Δp, Impulse
kgm/s,Ns
Conservation of Momentum piT=pFT
Impulse=Δp=FΔt
Constant Velocity
a=
Dv
Dt
d Dy = y f - yi
Dx
vs =
v=
t Dx = x f - xi
Dt
Constant Acceleration
Dv = v f - vi Dy = y - y
f
i
Dx = x f - xi
2
ag=-9.8m/s
The Two equations of Motion
1.
2.
v f = vi + at
1
Dx = vi t + at 2
2
The Two equations of Motion
for Falling Objects
v f = vi + agt
1
Dy = vi t + agt 2
Fnet = F1 + F2 + F3 +...Fn
Forces
Fnetx = F1x + F2 x + F3x +...Fnx
Fnety = F1y + F2 y + F3y +...Fny
Fnet = ma
Fg =
Gm1m2
r2
G = 6.67x10-11
W = mg = Fg = mag
mv 2
Fc =
r
v=
2p r
T
Nm 2
kg 2
Work Stations
• Objective
• You will derive the essential components of work.
Engage: Write around each of the following questions.
1. What do you think physical work is?
2. What factors do you think go in to making more or less physical
work?
3. If you could guess at what a work equation would equal, what would it be? 1
minutes
W=
Work Stations Continued
Explore: Explore each stations and answer the explain questions for each. 16 min
Station 1 Pulley Station.
Station 7 Elasticity
Station 2 Lever Station.
Station 3 Wheel & Axle Station
Station 4 Pendulum Station
Station 5 Screw
Station 6 Dominoes
Explain
Answer the following questions at each station…
a. How is this a demonstration of work being done?
b. What could be changed so that more work is done?
Work Stations Final
Elaborate
4. Work Class Discussion
1. Student groups write their equations of Work on the board (from Engage activity)
2. W= FΔx
3. Units: kgm2/s2 or Nm
Evaluate
5. #E1 Work Practice
E#1 Work
a. W=?
F= 20N
Δx=30m
1.
2.
3.
4.
b. W=200 Nm
F= ?
Δx=60m
c. W=0.50 Nm
F= 3N
Δx=?
A box that weighs 575 N is lifted a distance of 20.0m straight up by a
cable attached to a motor. How much work is done by the motor?
Murimi pushes a 20 kg box 10 m across a floor with a horizontal force of
80N. Calculate the amount of work done by Murimi.
Lake Point Tower in Chicago is the tallest apartment building in the
United States. Suppose you take the elevator from street level to the
roof of the building. The elevator moves almost the entire distance at
constant speed, so that it does 1.15x105J of work on you as it lifts the
entire distance. If your mass is 60.0 kg, how tall is the building? Ignore
the effects of friction.
A hummingbird has a mass of about 1.7g. Supose a hummingbird does
0.15J of work against gravity, so that it ascends straight up with a net
acceleration of 1.2m/s2. How far up does it move?
Pinning It!
Objective:
Students will derive the essential components of work
and potential energy.
Engage
1. What is energy? Come up with a definition for energy based on your
current understanding of what energy is.
2. Today we will drive a push pin into a block of wood by dropping a pingpong ball and a golf ball on it. Predict what will happen in each case, and
give reasons based on the physics concepts that you’ve already learned like
time, force, acceleration, velocity or momentum.
Explore & Explain
Explore and Explain
3. Try to drive the push pin into the block then explain…
a) How the activity shows connection to work.
b) What would you do to do more work on the push pin?
Elaborate Question: What is potential energy? What is kinetic Energy
4. Short Lecture: Potential Energy -> Kinetic Energy -> Work
5.
6.
Energy is transferred in this example so complete the sentence.
Potential Energy is converted to _______ energy as the ball falls
towards the pin. When the ball smashes into the pin it does _____
on the pin causing the pin to push into the wood.
Draw a diagram of the activity where you will show the energy
transfers and work being done.
Evaluate
7. E#2 Potential Energy & Work
EH#2 Potential Energy & Work
a. m=20kg
h=10m
U=?
b. Ui=40 J
Uf=10 J
W=?
c. Ui=80J
Uf=?
W=20J
d. Ui=80J
Uf=30J
F=20N
d=?
1. How much does the potential energy of a 2kg
rock increase when you throw a rock straight up in
the air and it reaches its maximum height 20 m
above your head?
2. How much work did you do in problem 1?
3. What is the potential energy of a 400 kg anvil that
is 10 meters above the ground?
4. How much work is done by gravity when a 12,000
kg meteor falls 10,000 m to earth and crashes?
E#3 Kinetic Energy & Work
a.
Kf=0
Ki=100 J
W=?
b.
Kf=0
Ki=20 J
W=200J
c
Kf=50
Ki=100 J
W=?
F=20N
Δx=?
d.
ΔK=80 J
W=?
F=?
Δx=20m
1. How much Kinetic Energy is gained when a 0.5 kg
acorn drops from a tree branch 10 m high until the
instant before it hits a stool 2m above the ground? KE=39.2 J
2. Find the Force applied by a hammer on a nail if the
hammer hits the nail with a Kinetic Energy of 8600 J
and and the nail sinks 0.5 m into the wooden beam. Fap=1.72x104 N
E#4 Work & Energy Conversions
1.
2.
3.
4.
5.
6.
Using 1000. J of work, a small object is lifted from the ground floor to the
third floor of a tall building. How much potential energy did it gain?
A platform diver weighs 500 N. She steps off a diving board that is
elevated to a height of 10 meters above the water. The diver will possess
___ Joules of kinetic energy when she hits the water.
A ball is projected into the air with 100 J of kinetic energy. The kinetic
energy is transformed into gravitational potential energy on the path
towards the peak of its trajectory. The kinetic energy at the peak of its
trajectory is ______ Joules. When the ball returns to its original height, its
kinetic energy is ____ Joules.
During a construction project, a 2500 N object is lifted high above the
ground. It is released and falls 10.0 meters and drives a post 0.100 m into
the ground. The average impact force on the object is ____ Newtons.
A 50-kg platform diver hits the water below with a kinetic energy of 5000
Joules. The height (relative to the water) from which the diver dove was
approximately ____ meters.
Which requires more work: lifting a 50.0 kg crate a vertical distance of
2.0 meters or lifting a 25.0 kg crate a vertical distance of 4.0 meters?
This Too Shall Pass
Picture Analysis
1. For each of the following pictures from the music video
you just watched.
a. Draw the part of the picture where an energy transfer takes place.
i. Label the type of energy gained or lost (kinetic, potential, or work done)
b. After drawing, pass your papers clockwise. Comment on the paper passed to you.
i.
Identify one thing on the labeled drawing that you think is correct.
a. Explain why so that it will be easy for the paper’s owner to understand.
ii. Identify one thing on the labeled drawing that you would change.
a. Explain why so that it will be easy for the paper’s owner to understand.
HW E#5
10m
If Mr. A (m=67.6 kg) is standing on a diving board
10 meter above the ground, what is his Potential
Energy and Kinetic Energy when he is 10m, 7.5 m,
5.0m, and 2.5m and 0 m from the ground?
7.5m
5.0m
2.5m
0m
Potential Energy = 0
Kinetic Energy =6625J
E#5 Conservation of Energy
If Mr. A (m=67.6 kg) is standing on a diving board 10 meter above the
ground, what is his Potential Energy and Kinetic Energy when he is
10m, 7.5 m, 5.0m, and 2.5m and 0 m from the ground?
10m
E#6 Conservation of Energy
a.
A 70 kg person jumps from one stool to the
next. a) Find the potential energy on each
stool. The last stool falls down two meters
when the person jumps jumps on it. b)How
much potential energy did it lose? c) How
5m
3m
4m
much force does the person hit the stool
2m
with?
1. A 800 kg meteorite falls from the sky, hits the ground and makes a
crater 800 m deep.
a. How much work was done by the meteorite ?
b. How much kinetic energy did the meteorite gain from the long fall?
c. How high did the meteorite start out?
2. A car engine does 500 J of work. How much kinetic energy does the car gain if
we assume that friction is negligible?
3. A point guard bounces a 2kg basketball from 1.2 meters in the air.
a. How much potential energy does it have?
b. If the ball bounces back up only 0.7 m, how much energy was lost to the
surrounding area.
c. How much force should the basketball player apply in order to make the
ball bounce back up to its initial height?
Kinetic Energy EH#7
a. m=10kg
v=2m/s
K=?
b.
m=?
c. m=20 kg
v=6m/s
v=?
K=70 J
K=100 J
d. What is mechanical
energy? What is the
equation for
Conservation of
Mechanical Energy?
When is mechanical
energy not conserved?
1. Calculate the kinetic energy of a 8kg object moving at a velocity of 4m/s.
2. A 2000 kg car is traveling at 40 m/s, what is its kinetic energy?
3. Three marbles (0.05 kg each) roll across the table with a speed of 2 m/s each in
different directions. What is the total Kinetic Energy of this three ball system.
4. A helicopter has 20,000 J of kinetic energy with a mass of 2000 kg. How fast is it
moving?
Energy of Motion Lab
Engage
1. What if we lowered the height of your ramp from yesterday. What effect would that
have?”
Explore
2. Take at least 5 data points, for different heights of the ramp and find the
corresponding velocities at the bottom of the ramp.
Explain
3. Graph the data in a way that makes sense to you and explain what knowledge you
can get from the data.
Elaborate
4. U= mgh, and ∆U = K. So instead of graphing height vs velocity, let’s graph K vs v
continue
5. “How does v change with K? L
a. Let’s square v and graph K vs. v2 and see what happens.
6. What kind of graph is this?
a. What does the slope of the graph mean?
Linear y = m x + b
K = (½ m) v2 + 0
Therefore, we have modeled that K = ½ m v2.
Note: Our data won’t be perfect because some energy is “lost” to rotation.
Evaluate
7. E#7 on KE = ½ m v2
EH#8 Energy Transfer
Practice
A 6 g marble is rolled down a 5 m ramp. Assuming that
friction and rotational energy lost are negligible, answer the
following questions.
1. What is the initial potential energy of the marble?
2. What is the Total Mechanical Energy of the system?
3. What is the potential energy when the ball is 1.5 m
above the ground?
4. What is the kinetic energy when the ball is 1.5 m from
the ground?
5. What is the speed of the ball when it is 1.5 m from the
ground?
6. What is the final kinetic energy of the ball?
7. What is the final speed of the ball?