Section 04 — Forces & Balance

Course: LBS 120 – Physics with Lab

Learning Session

Explore These Materials: 1. Read (45 min) — Newton’s Laws overview; Free‑body diagrams (short primer). Static vs kinetic friction (key ideas).
2. Watch (60 min) — Vectors and equilibrium; Torque and levers (intro lab demos).
3. Listen (30 min) — Everysection forces: bicycles, doors, ramps.
4. Observe — Find a door that “feels heavy.” Where is the handle? Sketch forces and torque.

Key Quote Box

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Practice

1. Free‑Body Sketches — Draw FBDs for a book on a table, a person leaning on a wall, and a cart on an incline; label forces.
2. Lever Lab — Use a ruler as a lever with a small weight; find balance points; relate torque τ = r × F.
3. Friction Coefficient — Slowly increase incline for a small object until it slips; estimate μ_s = tan(θ); note uncertainties.
4. Equilibrium Build — Stack objects into a stable tower; explain stability using center of mass and base of support.
5. Reflection — How did diagrams alter what you noticed about forces in daily life?

Hard Problem (Optional)

Predict the angle at which an object will begin to slide for different surfaces; test and compare to μ_s estimates. Explain discrepancies.