Buoyancy & Archimedes' Principle – AP Physics 1

Learning Objectives

State Archimedes' principle: buoyant force equals weight of displaced fluid

Predict sink, float, or neutrally buoyant based on density comparison

Calculate buoyant force: F_b = ρ_fluid · V_disp · g

Analyze force balance on submerged and floating objects

Key Equations

\( F_b = \rho_f V_{disp} g \)

\( \rho_{obj} < \rho_f \Rightarrow \text{floats} \)

\( \rho_{obj} = \rho_f \Rightarrow \text{neutral} \)

\( \rho_{obj} > \rho_f \Rightarrow \text{sinks} \)

\( \frac{V_{sub}}{V_{total}} = \frac{\rho_{obj}}{\rho_f} \)

Why It Matters

Archimedes' principle explains why ships float, submarines dive, and hot-air balloons rise. It governs density measurement, hydraulic engineering, and even how fish control their depth with swim bladders.