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Monday, October 13, 2025

Analysis of Moments (HTML5) — Interactive Lever Simulator 2/3 by Jin Sheng

Analysis of Moments (HTML5) — Interactive Lever Simulator by Jin Sheng

Overview

Analysis of Moments is a plain HTML5 + Canvas interactive that lets learners explore how forces and their perpendicular distances from a pivot produce moments. With live construction lines, automatic calculations, and a clear result panel, students can see—at a glance—whether a lever balances or tends to rotate clockwise/anti-clockwise.

02Analysis_of_Moments_20251013/
02Analysis_of_Moments_20251013.zip

Built for workshops and classroom use, this lightweight tool runs anywhere—no plugins, no LMS lock-in—and embeds cleanly in SLS as a Plain Web/HTML5 object.

What makes this build effective

1) Hands-on geometry of moments

  • Angle presets (0°, 30°, 45°, 60°, 90°) and a Flip control instantly change lever orientation.

  • Drag the red pivot along the lever to change the moment arm geometry.

  • Construction lines (toggle on/off) show perpendicular distances clearly—no guesswork.

2) Rich force configuration (up to 8 forces)

  • Each force has its own name, magnitude, direction (↑ ↓ ← →), position along the lever, colour, and visibility toggle.

  • The UI shows d⊥ for every force, so students connect “moment = F × d⊥” to a visible distance on the diagram.

3) Transparent calculations & verdict

4) Classroom-friendly UX

  • Collapsible DIAGRAM / CALCULATIONS / RESULT panels reduce on-screen clutter.

  • Center and Reset ALL buttons make it easy to begin new trials.

  • Fully responsive layout for laptops, projectors, and tablets.

Learning objectives

By the end of the activity, learners can:

  1. Define moment of a force and identify clockwise vs anti-clockwise moments about a pivot.

  2. Determine and explain perpendicular distance (d_\perp) from pivot to force line of action.

  3. Compute ( \sum \text{moments}_\text{ACW} ) and ( \sum \text{moments}_\text{CW} ) and decide if the lever is in equilibrium.

  4. Predict how changing force, direction, lever angle, or pivot location affects balance.

  5. Explain common misconceptions (e.g., using the slanted distance instead of perpendicular distance).

Suggested lesson flow

1) Elicit & predict

  • “If we keep the lever horizontal and move the pivot left, what happens to the anti-clockwise sum?”

  • “Which changes more: increasing F or increasing (d_\perp)?”

2) Investigate

  • Add two forces on opposite sides—vary magnitudes and positions—observe the result.

  • Turn on construction lines to check (d_\perp).

  • Use angle presets and Flip to test non-horizontal beams.

3) Explain

  • In CALCULATIONS, read off the symbolic expression (e.g., ( F_1 d_{\perp1} + F_3 d_{\perp3} )) then the numeric line.

  • Link the Result statement to the sign and size of the difference.

4) Apply

  • Balance tasks: “Make the lever just balanced” (tolerance < 0.1).

  • Design tasks: “Place two unknown forces to balance a 60 N downward force at 75% along the lever.”

Misconceptions to target

  • Using slanted distance instead of perpendicular distance.

  • Assuming bigger F always wins: remind students that small F × large (d_\perp) can beat large F × small (d_\perp).

  • Mixing up direction of rotation from left/right or up/down forces—use pivot geometry to reason it out.

Quick challenges (ready to use)

  1. Balance the beam (tolerance < 0.1):

    • (F_1 = 20\text{ N}) down at 80% along the lever (right side).

    • Find a position for (F_2 = 25\text{ N}) up that balances.

    • Screenshot the CALCULATIONS panel as evidence.

  2. Minimal change puzzle:

    • With three forces placed, achieve balance by changing only one variable: either one magnitude or one position.

  3. Angle sensitivity:

    • Keep forces fixed. Compare outcomes at 0°, 45°, 90°.

    • Explain why (d_\perp) changes with angle even when the slider percentage doesn’t.

SLS integration (Plain Web/HTML5)

  • Upload the folder and point to index.html via Add Media → Web/HTML5.

  • Or embed on a site/blog:

<iframe src="index.html" width="900" height="640" style="border:1px solid #ccc;border-radius:8px"></iframe>

Tip: Keep construction lines on for guided practice; turn them off for mastery checks.

For teachers: assessment ideas

  • Exit ticket: “Explain why a 10 N force can balance a 40 N force.” (Look for (d_\perp) reasoning.)

  • Error analysis: Give an incorrect student solution using slanted distance; ask students to correct it.

  • Design brief: “Create a balanced system with exactly three visible forces; submit screenshot + moment sums.”

Credits & links

Why this model works

  • Concept-first visuals: Perpendicular distance is drawn, not assumed.

  • Immediate feedback: Sums and verdict update live, reinforcing definitions.

  • Flexible geometry: Angle presets, flip, and draggable pivot surface rich “what-if”s.

  • Lightweight & portable: Pure HTML5—perfect for workshops, low-bandwidth classrooms, and SLS embedding.

Want me to add a Teacher Guide PDF (learning goals, tasks, rubrics) or a student worksheet aligned to this interactive? I can generate either in your preferred format.

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