Explicit physics instruction
Floating equilibrium requires upward buoyant force to balance downward weight.
Average density includes hollow spaces; this is why a large ship can have lower average density than water.
Stability depends on shape, center of mass, and how buoyant force shifts with tilt.
Core relations: ρ=m/V; F_b=weight of displaced fluid.
Worked example
A floating object displaces exactly enough fluid that displaced-fluid weight equals object weight.
Guided question
Why can hollowing a metal shape make it float?
Independent work
- Solve three density/buoyancy problems.
- Draw one fluid force diagram.
- State one assumption or uncertainty.
Misconception check
A heavier object can float if its average density is low enough and it displaces sufficient fluid.
Formative check
What sets buoyant-force magnitude in Archimedes’ model?
Reveal response
The weight of the displaced fluid.
Mentor evidence conference
Ask Archaemenes to audit density units, displacement reasoning, and force balance.
Teacher guidance
Foundation: Calculate density and identify buoyant direction.
Core: Apply Archimedes’ principle and equilibrium.
Extended: Analyze stability and uncertainty.