Essential question: How do interaction forces produce changes in motion? This is an introductory bridge toward HS-PS2-1, the Newton's second-law modeling performance expectation. Students reason about interaction arrows, inertia and signed external force sums before later Newton's-law investigations. Week 06 alone does not claim full HS-PS2-1 mastery.
Prerequisites: signed number lines, graph and velocity ideas from Physics Weeks 02–05, basic algebra, units kg, m/s and m/s². Begin with a body boundary and a declared coordinate direction. Do not draw motion as a force. Distinguish force diagrams on a book from interaction pairs involving book/table and book/Earth.
Monday — Newton's First Law
Phenomenon: A cart can already move at +3 m/s while net force is 0 N. The stationary and moving balanced presets should show the same acceleration but different starting velocities. Distinguish ideal inertial motion from real-world friction/air drag.
Flow: 8 min prediction; 17 min shared reading and misconception checks; 15 min paired model cases; 10 min explanation; 5 min exit response.
Expected: ΣFx=+6−6=0 N, a=0 m/s²; the cart can still move at +3 m/s.
Phenomenon: A table supports a book. Weight is Earth ON book, normal is table ON book. For m=4 kg without additional vertical forces, normal and weight each have magnitude 39.2 N and sum to 0 vertically.
Probe: Ask whether weight and normal form a Newton's third-law pair. Answer no: both act ON the book. Interaction pairs involve two different objects.
Extra pull: Fup=5 N gives N=34.2 N with no loss of contact.
Math example: On the block with right positive, 14 N right and 6 N left yield ΣFx=+8 N. Mass 4 kg gives ax=+2 m/s². Weight 39.2 N down and normal 39.2 N up balance if vertical external forces are absent.
Extension: An object initially moving right under negative horizontal acceleration might slow before reversing. Ask students to distinguish acceleration direction from velocity sign.
Core lab: Use the Force Builder. Begin with the balanced/moving preset, then compare +8 N net on 2 kg versus 4 kg. Record predicted a=4 and a=2 m/s². Change only one variable at a time and export the notebook.
Model boundaries: All horizontal force sliders are prescribed forces, not a dynamic friction law. Gravity constant g=9.8 m/s². Contact stays enforced; N=mg+Fdown−Fup is positive in permitted ranges. Predicting v(t) and displacement over 2 seconds presumes unchanged forces and contact.
Target: Explain why net external force changes acceleration, not necessarily the direction of existing motion. Two signed force sums, mass/acceleration with correct units, forces on a single body, and at least one real-world limitation.
Friday's ten-question quiz is sampled from twenty public practice items and is not a confidential proctored exam; answers are in browser code. Human teachers review the separate written portfolio evidence before any authoritative evaluation.
Accurate, bounded statement about net force, velocity or interaction.
Math evidence · 4
At least two correct numerical vector sums or acceleration comparisons, with signed SI units.
Free-body diagram · 4
Single chosen object, correctly identified force agents, arrow directions and contact assumptions.
Reasoning · 4
Connects ΣF=ma to acceleration and Newton's first law to constant velocity.
Limitation/correction · 4
Identifies one omitted physical effect and corrects a misconception with evidence.
Review target: 16/20 = 80%. Teacher-reviewed work remains separate from browser quiz scores, and formal midterms/finals follow an authorized supervised process.
Accommodation and stretch
Foundation: use a number line, color-coded arrows, and a partially labeled FBD; give mass=4 kg and easy whole-number force sums.
Core: create three independent trials and derive acceleration from ΣFx/m before comparing with the model output.
Extension: add optional Fup and Fdown, derive N from vertical equilibrium, and explain why equal force magnitudes on one body are not automatically third-law pairs. Critique use of constant force when real sliding friction changes.
Existing `khae_high_science_evidence_v1:` daily evidence fields are retained. Standalone new lesson notes are stored under a different browser key and exported as portable JSON. No secret assessment keys, third-party runtimes or active STOS components are included.