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AP PHYSICS 1
(SECONDARY)
ESSENTIAL UNIT 5 (E05)
(Work & Conservation of Energy)
(Giancoli Chapter 6)
(July 2015)
Unit Statement: Previous units the translational motion of an object in terms of Newton’s three
laws where force plays the central role in determining motion. In this unit, an alternative analysis
of translational motion will be discussed. Unit 5 will discuss the motion of objects in terms of
quantities of energy and work. (Estimated class time three weeks)
Essential Outcomes: (must be assessed for mastery)
1. The Student Will define open and closed systems for everyday situations and apply
conservation concepts for energy to those situations. (LO 5.A.2.1, SP 6.4, SP 7.2)
2. TSW will justify that an object can only have kinetic energy since potential energy
requires an interaction between two or more objects. (EK 5.B.1)
3. TSW analyze a scenario and make claims (develop arguments, justify assertions) about
the forces exerted on an object by other objects for different types of forces or
components of forces. (LO 3.A.3.1, SP 6.4, SP 7.2)
4. TSW explain that a system with internal structure can have potential energy. And that the
work done by a conservative force is independent of the path taken. (EK 5.B.3)
5. TSW justify that since energy is constant in a closed system, changes in a system’s
potential energy can result in changes to the system’s kinetic energy and the
changes in potential and kinetic energies in a system may be further constrained by
the construction of the system. (EK 5.B.4)
6. TSW make claims about the interaction between a system and its environment in which
the environment exerts a force on the system, thus doing work on the system and
changing the energy of the system (kinetic energy plus potential energy) (5.B.5.4)
7. TSW will determine work is defined as energy that can be transferred by an external
force exerted on an object or system that moves the object or system through a
distance. (EK 5.B.5)
8. TSW analyze data to calculate energy transfer and work done on or by an object or system.
9. TSW define power as the rate of energy transfer into, out of, or within a system.
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Implied and Practiced Outcomes:
1. The Student Will demonstrate and calculate work and work-kinetic energy theorem.
2. TSW demonstrate conservative forces and potential energy as they apply to gravity and
springs.
3. TSW calculate and demonstrate conservation of mechanical energy.
4. TSW define, calculate and demonstrate power.
5. TSW use Hooke’s Law to calculate work, force and energy.
Guided or Essential Questions:
 How is energy of a system defined?
 How is work represented graphically?
 What is the mechanical energy and what factors affect its conservation?
 How are humans dependent upon transformations of energy?
 If you hold an object while you walk at a constant velocity, are you doing work on the
object? Why or why not?
 What factors affect the collision of two objects, and how can you determine whether the
collision is elastic or inelastic?
 How can changes in momentum be utilized to determine the forces applied to an object?
Key Concepts:
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Work
Potential Energy
Gravitational Potential Energy
Law of Conservation of Energy
Power
Horse Power
Non Conservative Forces
Spring Equation
Energy
Kinetic Energy
Elastic Potential Energy
Work-Energy Principle
Watt
Dissipative Forces
Conservative Forces
Hooke’s Law
Some Common Equations for this Unit:
𝑊 = 𝐹𝑑 𝑐𝑜𝑠𝜃
W= F||d
𝑊𝑛𝑒𝑡 = 𝐹𝑛𝑒𝑡 𝑑 𝑐𝑜𝑠𝜃
KE = ½ mv2
𝑊𝑛𝑒𝑡 = ∆𝐾𝐸
𝑃𝐸𝑔𝑟𝑎𝑣 = 𝑚𝑔𝑦
𝐹𝑠 = −𝑘𝑠
elastic PE= ½ kx2
𝑊𝑛𝑐 = ∆𝐾𝐸 + ∆𝑃𝐸
KE2 + PE2 = KE1 + PE1
Or
E2 = E1= constant
Work defined as constant force
Work when force is parallel to the displacement
Net work
Translated Kinetic Energy
Work Energy
Gravitational Potential Energy
Spring Equation or Hooke’s Law
Elastic Potential Energy
Work Energy Principle (general form)
Conservation of Mechanical Energy
Power
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Schedule of suggested laboratory experiments (guided inquiry format is suggested for labs
shaded in gray)
TSW #
Lab #
Name of Laboratory
Description of Lab
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Sports Ball Energy
Quick lab- Each lab group is given a sport ball. With the
ball at rest, students must identify the closed, isolated
system. Students then discuss and choose one way in
which to change the kinetic or potential energy of their
ball. As students explain how their energy change takes
place, they will need to be guided toward the idea that
an outside force is needed.
Each lab group is provided with a friction brick, a spring
scale and 500 g mass. The goal for students is to observe
how applied forces carried at an angle is applied, and how
this impacts the work being done on the block. The mass
may or may not be used, depending on the curiosity of the
students.
Students will investigate the relationship between the
force applied to a spring and the distance the spring
stretches
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Angles and Work
Hooke’s Law
Associated Science
Practices
1.1, 1.2, 1.3, 1.4,
1.5, 2.1, 2.2, 3.1,
4.1, 4.2, 4.3, 5.3,
6.1, 6.4, 6.5, 7.2
1.1, 1.2, 1.3, 1.4,
1.5, 2.1, 2.2, 3.1,
4.1, 4.2, 4.3, 5.3,
6.1, 6.4, 7.2
1.1, 1.2, 1.3, 1.4,
1.5, 2.1, 2.2, 3.1,
4.1, 4.2, 4.3, 5.3,
AP College Board – see link below
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Hooke’s Law Revisited
Hooke’s law is revisited to challenge students in the use
of force-versus distance graphs for the determination of
work done on (or by) a spring. Each small group is given a
spring and a variety of masses, and students must
determine a graphical way of predicting the work done
on the spring by each mass. Then, given a specific
amount of work (randomly assigned), students must
predict what mass is required to produce that amount of
work and what displacement the mass will give the
spring. In the final stage of this activity, students must
design and implement a plan to test their prediction.
Each group’s percent error determines the grade they
receive for the lab.
6.1, 6.4, 7.2
1.1, 1.2, 1.3, 1.4,
1.5, 2.1, 2.2, 3.1,
4.1, 4.2, 4.3, 5.3,
6.1, 6.4, 7.2
Suggested Materials:
1. Giancoli, D.C. Physics: Principles with Applications. Englewood Cliffs, NJ: Pearson
Education.
2. Appel, K, Ballen, C, Gastineau, J, Vernier, D. Physics with Vernier. Beaverton, OR;
Vernier Software and Technology, 2010.
3. Puri, O; Zober, P. Physics. A laboratory manual; Boston, Mass. N.Y: Pearson Custom
Pub., 2002. 8th edition
4. Hieggelke, Curtis J., David P. Maloney, and Stephen E. Karim. Ranking Tasks: “Equal
Forces on Boxes- Work Done a Box”
Suggested Technology Resources:
Labs, in class activities, quizzes, videos and demos:
 5.1 Web Activity- TSW 3- Students use ActivPhysics simulation that them through a
four situations in which work is calculated.
http://media.pearsoncmg.com/bc/aw_young_physics_11/pt1a/Media/WorkEnergy/Work
Calculations/Main.html
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Work Done on a Spring- Interactive Lab lesson. Helps students see the graphical analysis of the
spring. http://webphysics.davidson.edu/physlet_resources/bu_semester1/index.html
Hooke’s Law Labhttp://apcentral.collegeboard.com/apc/members/courses/teachers_corner/39138.html
Rubber Band Science
http://www.newton.dep.anl.gov/askasci/phy00/phy00525.htm
Video- need USA or Canadian VPN- Conservation of Energy
http://www.learner.org/resources/series42.html?pop=yes&pid=560
Note- All links to online resources were verified before publication. In cases where links are no longer
working, we suggest that you try to find the resource by a keyword internet search.
RUBRIC FOUND ON FOLLOWING PAGE……………………………
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SUGGESTED RUBRIC AP PHYSICS 1 E05
Student Name: __________________________
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Date: _______________________
To receive a ‘B’, the student must show ‘B’ level mastery on all essential outcomes (TSW’s).
The teacher’s discretion on the student’s holistic performance on the unit, including such items as: the above ‘A’ level rubric, the unit project, group work and class
discussions will determine ‘A’ level mastery.
If grading for AP test preparation, please refer to Course Outcome Rubric.
The Student Will
1. TSW define open and closed systems for
everyday situations and apply conservation
concepts for energy to those situations. [LO
5.A.2.1, SP 6.4, SP 7.2]
2.TSW will justify that an object can only have
kinetic energy since potential energy requires an
interaction between two or more objects. [EK
5.B.1]
3. TSW analyze a scenario and make claims
(develop arguments, justify assertions) about the
forces exerted on an object by other objects for
different types of forces or components of forces.
[LO 3.A.3.1, SP 6.4, SP 7.2]
4. TSW explain that a system with internal structure
can have potential energy. And that the work done
by a conservative force is independent of the path
taken. [EK 5.B.3]
5. TSW justify that since energy is constant in a
closed system, changes in a system’s potential
‘A’* LEVEL
Translates between a representation of a single object,
which can only have kinetic energy, and a system that
includes the object, which may have both kinetic and
potential energies.
Uses force and velocity vectors to determine qualitatively
or quantitatively the net force exerted on an object and
qualitatively whether kinetic energy of that object would
increase, decrease, or remain unchanged. [LO 3.E.1.3, SP
1.4, SP 2.2]
Applies mathematical reasoning to create a description of
the internal potential energy of a system from a description
or diagram of the objects and interactions in that system.
Calculates changes in kinetic energy and potential energy of
a system, using information from representations of that
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‘B’ LEVEL
Accurately defines and uses the concepts to justify
energy related situations.
For example:
If you throw a rock straight up outside, it eventually
returns to your hand with the same speed that it had
when it left, neglecting air resistance. What would
happen if you were to throw the rock straight up in the
same way, but while inside the classroom? Compared to
the speed with which it left your hand, after rebounding
off of the ceiling it would return to your hand with…..
Justify your answer.
Sets up a representation or model showing that a single
object can only have kinetic energy and use information
about that object to calculate its kinetic energy.
Makes predictions and calculations about the changes in
kinetic energy of an object based on considerations of the
direction of the net force on the object as the object
moves. [LO 3.E.1.1, SP 6.4, SP 7.2]
Students must master both points
Describes and makes qualitative and/or quantitative
predictions about everyday examples of systems with
internal potential energy
and
Makes quantitative calculations of the internal potential
energy of a system from a description or
diagram of that system
Makes predictions and justifications about the internal
energy of systems.
Comments
energy can result in changes to the system’s
kinetic energy and the changes in potential and
kinetic energies in a system may be further
constrained by the construction of the system. [EK
5.B.4]
system.
For example:
6. TSW make claims about the interaction between a
system and its environment in which the
environment exerts a force on the system, thus
doing work on the system and changing the
energy of the system (kinetic energy plus potential
energy) (5.B.5.4)
7. TSW will determine work is defined as energy
that can be transferred by an external force
exerted on an object or system that moves the
object or system through a distance. (EK 5.B.5)
Designs an experiment and analyzes data to examine how a
force exerted on an object or system does work on the
object or system as it moves through a distance. (LO
5.B.5.1)
For Example: A dart of mass m is accelerated horizontally
through a tube of length L situated a height h above the
ground by a constant force F. Upon exiting the tube, the
dart travels a horizontal distance Δx before striking the
ground, as depicted in the diagram below.
(a) Develop an expression for the velocity of the dart, v, as
it leaves the tube in terms of Δx, h, and any fundamental
constants.
(b) Derive an expression for the kinetic energy of the dart
as it leaves the tube in terms of m, Δx, h, and any
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1. Bowling Ball A is dropped from a point halfway up a
cliff. A second identical bowling ball, B, is dropped
simultaneously from the top of the cliff. Comparing the
bowling balls at the instant they reach the ground, which
of the following are correct? Neglect air resistance.
(A) Ball A has half the kinetic energy and takes half the
time to hit the ground as Ball B.
(B) Ball A has half the kinetic energy and takes onefourth the time to hit the ground as Ball B.
(C) Ball A has half the final velocity and takes half the
time to hit the ground as Ball B.
(D) Ball A has one-fourth the final velocity and takes
one-fourth the time to hit the ground as Ball B.
(E) None of these are correct
Correct starting equations and valid concepts are used.
All mathematical steps are clearly shown but minor
errors yield wrong answer.
OR
Correct starting equations and valid concepts are used.
Correct final result is displayed but the mathematical
steps are hard to follow.
Predicts and calculates the energy transfer to (i.e., the
work done on) an object or system from information
about a force exerted on the object or system through a
distance. (LO 5.B.5.5)
For example: Bob pushes a box across a horizontal
surface at a constant speed of 1 m/s. If the box has a
mass of 30 kg, find the power Bob supplies given the
coefficient of kinetic friction is 0.3.
fundamental constants.
(c) Derive an expression for the work done on the dart in
the tube in terms of F and L.
(d) Derive an expression for the height of the tube above
the ground in terms of m, Δx, L, F, and any fundamental
constants.
(e) An experiment is then performed in which the length of
the tube, L, is varied, resulting in the dart traveling various
horizontal distances Δx which are recorded in the table
below.
8. TSW analyze data to calculate energy transfer and
work done on or by an object or system.
Use a grid to plot a linear graph of Δx2 as a function of L.
Use the empty boxes in the data table, as appropriate, to
record the calculated values you are graphing. Label the
axes as appropriate, and place numbers on both axes.
Designs an experiment and analyzes graphical data in
which interpretations of the area under a force-distance
curve are needed to determine the work done on or by the
object or system. (LO 5.B.5.2):
9. TSW define power as the rate of energy transfer
into, out of, or within a system.
Students must master both points
Predicts and calculates from graphical data the energy
transfer to or work done on an object or system from
information about a force exerted on the object or system
through a distance. (LO 5.B.5.3)
and
Predicts changes in the total energy of a system due to
changes in position and speed of objects or frictional
interactions within the system. [LO 4.C.1.2, SP 6.4]
Predicts and calculates the rate of energy transfer to (i.e.,
the work done on) an object or system from information
about a force exerted on the object or system through a
distance. (LO 5.B.5.5)
For example: Bob pushes a box across a horizontal
surface at a constant speed of 1 m/s. If the box has a
mass of 30 kg, find the power Bob supplies given the
coefficient of kinetic friction is 0.3.
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