Physics 7A DL 5 Overview DL 5
Brief Overview
These activities provide more practice applying the Energy-Interaction Model to physical
phenomena involving mechanical and thermal energies.
Activity 2.3 Creating Particular Models with Mechanical Energies
Purpose:
• Provide practice in relying on the logic of the model—in this case, the Energy-Interaction
Model—instead of on intuition, hunches or beliefs, or procedures that worked in other
situations.
• Introduction to the construct of work as a transfer of energy in terms of the product of force
and distance moved in a parallel direction.
• Practice using spring-mass potential energy changes.
Learning Outcomes:
• Having trust that “working through” the model, in this case, systematically using the energy-
interaction diagram will get you “to the correct answer,” even if it contradicts your hunches or
intuition.
• Realizing that only the indicators at the start and end of an interval matter, not the motion that
happens in between.
Activity 2.4 How We Use the Energy-Interaction Model
Purpose:
• Provide a chance to step back and reflect on the entire process of using the Energy-Interaction
Model
• Practice including thermal energy (due to dissipation or friction) with mechanical energy.
• Practice applying the Energy-Interaction Model to a physical system with an additional
unknown energy and reasoning with the model.
Learning Outcomes:
• Recognizing when the effects of friction are relevant and when to include thermal energy in a
system which is experiencing mechanical motion.
• Ability to apply and reason with the Energy-Interaction Model for physical systems with
additional energy.
Activity 2.5 Modeling with Quantitative Expressions of Mechanical Energies
Purpose:
• Practice thinking explicitly about the dependencies of mechanical energies on the indicators.
In particular, realizing for which indicators the algebraic sign is important and for which it is
not.
• Practice using the energy-interaction diagram to be sure of the algebraic signs in the various
expressions for the changes in mechanical energies.
Learning Outcomes:
• Become familiar with and comfortable using the algebraic expressions for changes in
gravitational PE and translational KE.
i. Understand and know that 𝛥𝑃𝐸𝑔 = 𝑚𝑔𝛥𝑦, height being the indicator.
1
ii. Understand and know that 𝛥𝐾𝐸 = 𝑚𝛥(𝑣 2 ), speed being the indicator.
2
1
iii. Understand and know that 𝛥𝑃𝐸sm = 2 𝑘𝛥(𝑥 2 ), distance from equilibrium being the
indicator.
Unit 2: Applying Models to Mechanical Phenomena DL 5
, Physics 7A Activity 2.3 DL 5
Creating Particular Models with Mechanical Energies
A) FNT 1:
Very briefly compare your group member’s responses to these parts of FNT 1 and put a short
answer on your board.
Each letter below corresponds to the letter in the FNT:
b) Does the question involve a parameter that you know to be an indicator of the change in a type of
energy? Which energy and what is the indicator?
c) Draw an energy-interaction diagram for Rock X with two lines of algebra:
• 1st line using ∆E’s with subscripts,
• 2nd line substitute in expressions for each ∆E. Do NOT solve for anything!
d)-e) Are there ANY differences in the Energy-Interaction diagrams for rocks X, Y, and Z?
f) What does your model predict with 100% certainty about the final speeds of each rock just before
they hit the ground? In light of the dropping ball and coffee filter activity, what aspect of the
physical phenomena could change your prediction regarding the final speeds of the rocks?
g) Discuss the intuitive ideas that different members of your group hold that “bug you the most,”
because they appear to contradict the Energy-Interaction Model’s prediction that all rocks have the
same final speed?
Whole Class Discussion
B) FNT 2:
a) Draw a complete energy-interaction diagram for this process. Write the expression you have for
work in terms of energy changes.
b) Substitute the expression for work in terms of force and distance moved, and solve for the force.
Whole Class Discussion
Continue to Next Page
Unit 2: Applying Models to Mechanical Phenomena DL 5
Brief Overview
These activities provide more practice applying the Energy-Interaction Model to physical
phenomena involving mechanical and thermal energies.
Activity 2.3 Creating Particular Models with Mechanical Energies
Purpose:
• Provide practice in relying on the logic of the model—in this case, the Energy-Interaction
Model—instead of on intuition, hunches or beliefs, or procedures that worked in other
situations.
• Introduction to the construct of work as a transfer of energy in terms of the product of force
and distance moved in a parallel direction.
• Practice using spring-mass potential energy changes.
Learning Outcomes:
• Having trust that “working through” the model, in this case, systematically using the energy-
interaction diagram will get you “to the correct answer,” even if it contradicts your hunches or
intuition.
• Realizing that only the indicators at the start and end of an interval matter, not the motion that
happens in between.
Activity 2.4 How We Use the Energy-Interaction Model
Purpose:
• Provide a chance to step back and reflect on the entire process of using the Energy-Interaction
Model
• Practice including thermal energy (due to dissipation or friction) with mechanical energy.
• Practice applying the Energy-Interaction Model to a physical system with an additional
unknown energy and reasoning with the model.
Learning Outcomes:
• Recognizing when the effects of friction are relevant and when to include thermal energy in a
system which is experiencing mechanical motion.
• Ability to apply and reason with the Energy-Interaction Model for physical systems with
additional energy.
Activity 2.5 Modeling with Quantitative Expressions of Mechanical Energies
Purpose:
• Practice thinking explicitly about the dependencies of mechanical energies on the indicators.
In particular, realizing for which indicators the algebraic sign is important and for which it is
not.
• Practice using the energy-interaction diagram to be sure of the algebraic signs in the various
expressions for the changes in mechanical energies.
Learning Outcomes:
• Become familiar with and comfortable using the algebraic expressions for changes in
gravitational PE and translational KE.
i. Understand and know that 𝛥𝑃𝐸𝑔 = 𝑚𝑔𝛥𝑦, height being the indicator.
1
ii. Understand and know that 𝛥𝐾𝐸 = 𝑚𝛥(𝑣 2 ), speed being the indicator.
2
1
iii. Understand and know that 𝛥𝑃𝐸sm = 2 𝑘𝛥(𝑥 2 ), distance from equilibrium being the
indicator.
Unit 2: Applying Models to Mechanical Phenomena DL 5
, Physics 7A Activity 2.3 DL 5
Creating Particular Models with Mechanical Energies
A) FNT 1:
Very briefly compare your group member’s responses to these parts of FNT 1 and put a short
answer on your board.
Each letter below corresponds to the letter in the FNT:
b) Does the question involve a parameter that you know to be an indicator of the change in a type of
energy? Which energy and what is the indicator?
c) Draw an energy-interaction diagram for Rock X with two lines of algebra:
• 1st line using ∆E’s with subscripts,
• 2nd line substitute in expressions for each ∆E. Do NOT solve for anything!
d)-e) Are there ANY differences in the Energy-Interaction diagrams for rocks X, Y, and Z?
f) What does your model predict with 100% certainty about the final speeds of each rock just before
they hit the ground? In light of the dropping ball and coffee filter activity, what aspect of the
physical phenomena could change your prediction regarding the final speeds of the rocks?
g) Discuss the intuitive ideas that different members of your group hold that “bug you the most,”
because they appear to contradict the Energy-Interaction Model’s prediction that all rocks have the
same final speed?
Whole Class Discussion
B) FNT 2:
a) Draw a complete energy-interaction diagram for this process. Write the expression you have for
work in terms of energy changes.
b) Substitute the expression for work in terms of force and distance moved, and solve for the force.
Whole Class Discussion
Continue to Next Page
Unit 2: Applying Models to Mechanical Phenomena DL 5
