Martin Kassam-Vargas
Unit: Energy (4)
SPH4U
Day 3: Kinetic Energy and Work Energy theorem
Time Circle:
Learning Goals
-
Be able to visualize change in kinetic energy
Understand the like between Work and Kinetic energy
Know when Work-Energy Theorem applies (i.e. no
change in other forms of energy)
Materials
White boards
Markers
Projector
Assessment (A) and DI (D)
Opportunities
Minds On…
30 min
Review some old topics which will be key for deriving the Work-Energy Theorem,
ask the students
-“What is Work? Examples? The formula?”
-“What is Kinetic energy? Can a slow moving truck have more kinetic energy than a
fast moving van? The formula?
-“What is Newton’s second Law?”
Write all this on the board
Than Push a chair with a constant force. With the class Consider the questions
-What is the total work done? Wt= 𝚺(F)cos(0)𝚫𝒅
-How else can we represent Force? 𝚺(F)=ma
-If I’m pushing the chair with constant force, what does that say about the
acceleration? What formula can we use? Acceleration is constant, 𝒗𝟐𝒇 = 𝒗𝟐𝒊 +2a𝚫𝒅
After substitution of the last 2 equations into the first we get the Work Energy
thermo. Discuss conditions it works under (other forms of energy held constant)
Action!
20 min
Work out an example question as a class
“ How much total work is required to move a 1500Kg moving van from 40 km/h to
100 km/h?”
Let students form groups of 3 or 4, give white board and markers to each group and
they solve the question as a group showing steps on the whiteboard
“A 27-g arrow is shot horizontally. The bowstring exerts an average force of 75 N
on the arrow over a distance of 78 cm. Determine, using the work-energy theorem,
the maximum speed reached by the arrow as it leaves the bow”
Take up as a class afterwards
Consolidate
Debrief
10 min
Show class the cartoon clip from My Little Pony
https://www.youtube.com/watch?v=0bjkM_y-Wps ” at 0:55 Rainbow dash flies
down to save his friend, is the Kinetic Work-Energy theorem applicable here? Why
or Why not? No, gravitational potential energy is changing
Homework: Find a cartoon scene where the Kinetic Work energy theorem is
applicable
Assessment: What
groups write on
whiteboard, and
interactive
discussions