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Friction, repose and loose soil

Audience: Upper-secondary education, Biology and Physics. Suggested time: 35–40 min. Status: technical draft; Biology and Physics teacher review pending. Starting lesson: Angle of repose (repouso-solo). Resources: WebGL browser, paper or spreadsheet, and laboratory access. Follow the common preparation.

Objective

Relate sliding resistance to geometry and soil movement, without confusing material redistribution with mass creation or destruction.

BNCC

Proposed association: EM13CNT101, EM13CNT301 and EM13CNT302. See the mapping and official source in the general guide. Teacher review is needed.

Steps and records

  1. In 5 min, propose which configuration will allow more sliding and why.
  2. Open Angle of repose: A 15°/B 55°. The same disturbance prepares loose soil. Record day 0 and loose/deposited soil indicators under Living tunnels.
  3. Use the side camera and Show internal tunnels. Draw the pile and tunnels in both scenarios before resuming. Do not disturb another gallery.
  4. Advance one model day, pause and record moving soil, loose material, deposited material and balance error. Repeat until day 3.
  5. In 10 min, compare outlines and discuss why loose-soil quantity alone does not measure a slope’s angle. Save records and restore the backup.

Discussion questions

Annotated answer guidance

The lower threshold allows movement on inclinations where the higher one may retain resting material. Response depends on geometry and other forces; the loose total need not decrease more in either scenario. A near-zero balance is internal numerical consistency, not proof of realistic physics. If both stabilize early, record that and compare positions; do not alter only one scenario to manufacture a difference.

What the model does not represent

Soil uses aggregates and abstract volumes, not every physical grain. The angle is not a laboratory test or evidence of real tunnel safety. Cohesion, moisture, agents and geometry also influence this model.

Learning evidence

Submit a hypothesis, comparable records with days/units, a data-supported conclusion and one limitation. Use the general guide’s rubric; there is no required outcome.

Teacher review

Pending. No teacher or class was consulted to approve this guide. Record review and adjustments in the appropriate form before treating it as validated.

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