Complete five-day teaching notes, quantitative worked answers, model limitations, assessment guidance, differentiation and safe offline resources.
Instructional boundaries and standards
Essential question: How does work connect force, displacement and changes in speed? This week builds quantitative representations relevant to HS-PS3-1 and reinforces Newton's laws. Week 11 separately develops gravitational potential energy, the full conservation model and systems. Today's kinetic-energy work must distinguish work by ONE force from total NET work.
Prerequisites: vector directions, Newton's second law, cosine of 0°, 60°, 90°, 120° and 180°, positive mass, nonnegative speed, SI units, squares and square roots. Provide cosine values on a formula card for students without trigonometry background.
Monday — When does a force do work?
Launch 8 min: Compare holding a bag still with moving it. Clarify that work on the bag by a force depends on displacement and angle, and is zero if displacement is zero.
Reading 15 min: W=Fd cosθ; one joule=one newton-meter. At F=12 N, d=5 m: W(0°)=+60 J, W(90°)=0 J and W(180°)=−60 J.
Lab and evidence 22 min: Predict signs first, then record three virtual runs. Ask why a perpendicular force may still change velocity direction without doing work.
Concept: W=F⃗·d⃗. For constant force, work is the signed area of the parallel force-versus-displacement graph. For variable forces it is the integral ∫F_parallel dx; the constant-force shortcut cannot automatically be extended.
Worked answers: F=20 N, d=3 m, θ=60° → +30 J. θ=120° → −30 J. +10 N and −4 N parallel to +5 m displacement yield +50 J and −20 J respectively, so W_net=+30 J.
Exit: Explain how the angle affects work sign without changing force magnitude.
Concept: K=½mv² and W_net=K_f−K_i for constant mass, Newtonian conditions. Kinetic energy is nonnegative and work may be negative. The final speed magnitude is √(2K_f/m), but the theorem by itself cannot select the final direction.
Worked: For m=4 kg and v0=3 m/s, K_i=18 J. With +32 J NET work, K_f=50 J and speed magnitude 5 m/s. With −18 J net work, K_f=0. With −25 J net work, raw K_f=−7 J: impossible for the stated continued-motion scenario. The correct response is to revise the assumed interval, not to display an imaginary speed.
Setup: The work tool calculates work by a specified constant applied force; the kinetic-energy tool assumes the supplied work is net work across all external interactions. Students must never conflate the two.
Worked: Constant aligned 30 N through 4 m means work 120 J. Transfer lasting 4 s gives average signed power 30 W. A negative work transfer, −20 J over 5 s, gives −4 W.
Investigation: Three controlled work/angle trials; three controlled net-work/kinetic-energy trials; both exports, one numerical explanation, one model limitation and an 80% practice correction.
Required claim: Work is signed energy transfer by a force over displacement, while net work changes kinetic energy, and power describes transfer rate. At least two numerical worked cases with correct units and an explicit list of which interactions contribute to net work.
Counterclaim: A perpendicular force may do no work on an object. A negative-work result does not imply negative kinetic energy. Distinguish the work by one force from net work when others act.
Practice: The ten-question Friday quiz is randomly selected from 20 published learning questions. It is open-book and formative, not a confidential supervised midterm/final.
Correct distinction between signed work, total net work, kinetic energy and average power.
Numerical evidence · 4
Two or more correct worked examples with units, signs and relevant constants.
Mathematical reasoning · 4
Applies W=Fd cosθ and W_net=ΔK appropriately; respects K≥0.
Source and system · 4
Names the force agents, the moving object and whether results are synthetic.
Limitations and corrections · 4
Corrects at least one misconception and recognizes assumptions about constant force, mass or motion.
16/20 is the 80% review target. Human educators evaluate the actual submitted portfolio separately from open-book browser feedback. Closed-book official midterms/finals require a separate supervised process.
Teaching adjustments
Foundation: use integer force and displacement values at angles 0°, 90° and 180°; provide unit-conversion and cosine cards and the CSV in place of graphs. Core: analyze +/− work, 60° force projections and K_f for nonnegative cases. Extension: challenge students to distinguish instantaneous power F⃗·v⃗ from average power W/Δt and explain why integral work is needed for variable force.
The original khae_high_science_evidence_v1: learner-record keys remain untouched. New evidence stores under separate Week 10 local keys; no cloud sync is claimed. Dormant STOS assets remain unchanged.