Mechanics & Simple Machines · GCSE Physics Buoyancy & Density
Archimedes' Principle & Buoyancy Force Simulator
Key exam takeaway: Buoyant force depends ONLY on fluid density and displaced volume, independent of the object's own density or immersion depth once fully submerged.
- Client-side
- No Sign-up
- Live Derivation
- Projector Mode
- Print Worksheet
3D Simulation Stage● 60 FPS
Parameter Controls
cm³
g/cm³
g/cm³
%
Live Derivations & Metrics
Buoyant Force F_buoy
--
Object Weight G
--
Scale Reading
--
Displaced Volume
--
Real-Time Formula Derivation
Governing Formula:
--Substitution:
--Regime: --
Worked Examples & Exam Question Deep Dive
Worked Problem
Problem: A 500cm³ iron block is fully submerged in water (rho=1.0g/cm³) and in kerosene (rho=0.8g/cm³). Find buoyancy. (g=10N/kg)
Step-by-Step Derivation:
- 1) In water: F_buoy = 1000*10*5e-4 = 5N; 2) In kerosene: F_buoy = 800*10*5e-4 = 4N. Independent of iron density.
Worked Problem
Problem: An ice cube floats in a beaker of water. When melted, does the water level rise, fall, or stay unchanged?
Step-by-Step Derivation:
- Stays unchanged! While floating, V_disp = m_ice / rho_water. When melted, the resulting water volume is m_water / rho_water = V_disp, exactly filling the displaced cavity.
Student Inquiry Worksheet & Practice Problems
Q1. Variant 1: An ice cube floats in saltwater. Does the level rise, fall, or stay unchanged after melting?
Answer Key: Rises! Floating displacement V_disp = m / rho_salt < melted pure water volume V_melt = m / rho_water, raising liquid level.
Q2. Variant 2: How does a submarine control diving and surfacing?
Answer Key: By flooding or blowing water from ballast tanks, changing its own weight G while submerged volume V_disp and buoyancy remain constant.
Q3. Variant 3: An object weighs 8N in air and 5N when submerged in water. Determine volume and density. (g=10N/kg)
Answer Key: F_buoy = 8 - 5 = 3N. Volume V = 3 / (1000*10) = 3e-4 m³ = 300cm³. Density rho = 0.8 / 3e-4 ≈ 2667 kg/m³.
Frequently Asked Questions & Misconceptions
Do submerged objects resting on the bottom experience buoyancy?
Yes. As long as liquid contacts the bottom surface, upward hydrostatic pressure exceeds downward pressure. Buoyancy is zero only if the base is sealed to the bottom with no liquid underneath.
Does buoyancy increase as an object goes deeper?
No. Once fully submerged, displaced volume V_disp equals object volume V_obj and remains constant. While ambient pressure increases, the difference in pressure between top and bottom stays unchanged.
When a ship sails from river to sea, does buoyant force change?
No, buoyancy still equals the ship weight. But because seawater is denser, displaced volume decreases, causing the ship to float slightly higher.
Do hot air balloons use Archimedes principle?
Yes. Air is a fluid. Heating air inside reduces its density, making balloon gross weight less than the weight of displaced cool ambient air (F_buoy > G_total).