Download C - Physics Lessons 2

Lesson 2
Time Frame: 1:00 – 2:00
Grade: 12
Title: Mechanical Energy
Date: Tuesday, December 7th
Subject: Physics 30
Stage 1 – Desired Results
Established Goals (Outcomes):

PH30-CO1 Investigate the nature of kinetic, potential, and total mechanical energy, including the law of
conservation of energy.
Established Goals (Indicators):

Solve problems related to kinetic, potential, and total mechanical energy in which objects move with and
without the presence of friction. (K, S)
Understandings:
Students will understand that…

Gravitational Potential Energy is energy stored as a
result of the position of an object relative to
ground level or an arbitrary base level.
Gravitational Potential Energy (U) = Mass (m) x
Gravity (g) x Height (h)
An object possesses kinetic energy if it is in motion.
Kinetic Energy (K) = ½ x Mass (m) x Velocity (v)
Total mechanical energy is sum of gravitational
potential energy and kinetic energy and potential
energy of a spring (which we will discuss later).
Total mechanical energy remains constant (Law of
Conservation of Energy).
Work = Force x Displacement
TME in + Work = TME out
A force acting perpendicular to the object will not
change the work done.
Work will not be done unless the force acting on
an object can overcome the friction force.









Approaches Employed:





Technology (energy simulations)
Demonstration (interactive demonstration)
Take home notes (activity sheet with blanks
filled in)
Formative assessment (short story)
Real life connections (Engineering connection)
Essential Questions:





What are some ways engineers use the
mechanics of energy in their everyday work?
What kind of energy is being used when an
object is in motion?
What is stored energy?
Describe the Law of Conservation of Energy.
What has more potential energy: a boulder on
the ground or a feather 10 feet in the air?
Materials; Safety Considerations; Management
Considerations (assume class of 30)






Banana, battery, chair
3 basketballs, 2 racquet balls
3 fake bowling balls
30 activity sheets
Smart board with laptop
Problem Sheets (30)

Performance Task:


Assessment Activity sheets (30)
Stage 2 – Assessment Evidence
Other Evidence:
Solve problems related to kinetic, potential, and
total mechanical energy in which objects move
with and without the presence of friction
Closing Assessment Question



Assess how they play with or alter the
computer simulations. Look for expressions of
understanding.
Ability to determine height of racquet ball
using gravitational potential energy formulas.
Engagement during in class discussion
Stage 3 – Learning Plan
Time
Activity
5 min
1:00 – 1:05
Collect and discuss short story assignment
5 min
1:05 – 1:10
Engineering Connection







5 min
1:10 – 1:15
Ask for volunteers to read their story out loud.
Ask for volunteers to summarize their energy
transfer and ways of increasing efficiency.
Mechanical engineers are concerned about the
mechanics of energy — how it is generated,
stored and moved.
Product design engineers apply the principles of
potential and kinetic energy when they design
consumer products.
For example, a pencil sharpener employs
mechanical energy and electrical energy.
When designing a roller coaster, mechanical and
civil engineers ensure that there is sufficient
potential energy (which is converted to kinetic
energy) to move the cars through the entire
roller coaster ride.
Engineers need to understand the many different
forms of energy in order to design useful
products
Items containing Energy



Materials
Thing in common – Energy!
Banana – food contains chemical energy used by
your body as fuel.
Battery - The battery contains electrical energy
(in the form of electrical, potential or stored
energy), which can be used by a flashlight or a
portable CD player.
Items containing Energy



Banana
Battery
Chair

10 min
1:15 – 1:25
Interactive Demonstration






10 min
1:25 – 1:35
You standing on a stool - A person standing on a
stool has potential energy (sometimes called
gravitational potential energy) that could be used
to crush a can, smash the banana, or really hurt
the foot of someone standing under you
Ask for 6 volunteers.
Complete activity 1 in front of class (3 different
groups going at once)
Explain / discuss with class gravitational potential
energy and relate findings to formula for
gravitational potential energy.
Explain transfer of potential energy (student on
chair) to kinetic when student jumps off chair.
(ground absorbed your energy when you landed
and turned it into heat)
Complete activity 2 in front of class (2 different
groups going at once)
Explain / discuss with class kinetic energy and
relate findings to formula for kinetic energy.
Total mechanical energy simulations:



Show students mechanical energy simulations
which simulate the change in kinetic and
potential energy while total mechanical energy
remains constant.
Allow students to come to the front and change
forces / directions and see results.
Discuss what happens when you add a force.
2 min
1:35 – 1:37
Fill in blanks for activity sheet:
15 min
1:37 – 1:52
Solve problems related to kinetic, potential, and total
mechanical energy in which objects move with and
without the presence of friction:



Discuss concepts reviewed in simulation and
complete activity sheet.
In previous groups from yesterday, using your
observed heights, determine the height the
racquet ball would bounce to after energy
transfer using potential energy calculations.
Complete problems on worksheet as a group of 3
(previous double ball bounce groups) although,
Interactive Demonstration





3 basketballs
2 racquetballs
3 “fake” bowling balls
30 Activity sheets (ECUR 398 –
see page 1 of handout)
3 chairs
Total mechanical energy simulations:


http://www.physicsclassroom.c
om/Physics-Interactives/Workand-Energy
o Roller coaster.
http://phet.colorado.edu/en/si
mulations/category/physics/wor
k-energy-and-power
o Skate board park
Fill in blanks of activity sheet:

Activity sheets (30) (ECUR 398 –
see page 2 of handout)
Solve problems related to kinetic,
potential, and total mechanical
energy in which objects move
without the presence of friction:


Activity sheets from last class.
Problem sheet. (ECUR 398 – see
page 3-4 of handout)
every member must have their own sheet filled
out.
5 min
1:52 – 1:57
Engineering Connection Close:






3 min
1:57 – 2:00
Demonstrate a ball that you hold in your hand
has potential energy, while a ball that you throw
has kinetic energy.
These two forms of energy can be transformed
back and forth.
When you drop a ball, you demonstrate an
example of potential energy changing into kinetic
energy.
Energy is an important engineering concept.
Engineers need to understand the many different
forms of energy so that they can design useful
products.
An electric pencil sharpener - designer needs to
know the amount of kinetic energy the spinning
blades need in order to successfully shave off the
end of the pencil as well as choose an
appropriately-powered motor to supply the
necessary energy.
Closing Assessment Question:


What has more potential energy: a boulder on
the ground or a feather 10 feet in the air?
The feather because the boulder is on the ground
and has zero potential energy. However, if the
boulder was 1 mm off the ground, it would
probably have more potential energy.
Engineering Connection Close:

ball
Closing Assessment Question:

Note –If time is short this
question can be cut from the
end of this lesson and used in
the next lesson.