Buoyancy Experiment
Calculate buoyant force, displaced volume, and object density using Archimedes principle. Enter mass in air and apparent mass in water for physics results.
About This Calculator
The Buoyancy Experiment Calculator lets you replicate Archimedes' famous discovery using just two mass measurements: the weight of an object in air and its apparent weight when submerged in a fluid. The difference reveals the buoyant force, from which you can determine the volume of the object and its density — without needing to measure volume directly.
This calculator uses the Archimedes principle formula B = (m_air − m_water) × g, where B is the buoyant force in newtons, m_air and m_water are the mass readings in kilograms, and g = 9.80665 m/s² is standard gravity. From the buoyant force and the fluid density, the calculator derives the displaced volume (V = B / (ρ × g)) and the object's density (ρ_obj = m_air / V). This method works for any fluid — fresh water, salt water, oil, mercury, or custom-density liquids.
This experiment is a staple of high school and university physics labs for teaching fluid mechanics, density determination, and Archimedes principle. The calculator supports any mass scale readable to at least 0.001 kg (1 gram) for accurate results.
Regional Notes
India: Use kg and kg/m³ as SI units. Water density = 1000 kg/m³, gravity = 9.81 m/s².
United States: Convert lbm to kg (1 lb = 0.4536 kg) if using imperial scales. Water density 62.4 lb/ft³ converts to 1000 kg/m³.
United Kingdom: SI units are standard in UK science classrooms. Use digital scales in grams (0.001 kg resolution) for best results.
Frequently Asked Questions
What is Archimedes principle?
Archimedes principle states that the upward buoyant force exerted on a body immersed in a fluid equals the weight of the fluid the body displaces. This principle explains why objects float or sink.
How does the buoyancy experiment work?
You measure the mass of an object in air using a scale, then measure its apparent mass while fully submerged in water. The difference multiplied by gravity gives the buoyant force. From this you can compute the displaced volume and the density of the object.
What is the formula for buoyant force?
The buoyant force equals the weight of displaced fluid: B = (mass_in_air - apparent_mass_in_water) × g, or equivalently B = ρ × V × g where ρ is fluid density, V is displaced volume, and g is gravitational acceleration (9.81 m/s²).
Can I use this with fluids other than water?
Yes. You can enter any fluid density in kg/m³. Common values: fresh water 1000, sea water 1025, ethanol 789, mercury 13534. The calculator uses your custom fluid density to compute displaced volume and buoyant force.
How do I measure apparent mass in water?
Use a spring scale or digital balance. Suspend the object from the scale in air and record its mass. Then submerge the object fully in water without touching the container walls, and record the lower reading — that is the apparent mass in water.
Does the calculator account for different gravitational acceleration?
The calculator uses Earth standard gravity g = 9.80665 m/s². For locations at extreme altitudes or other planets, the result will differ slightly — Earth's gravity varies by less than 0.5% across its surface.
Why does an object feel lighter in water?
An object feels lighter in water because the fluid exerts an upward buoyant force equal to the weight of the displaced water. This reduces the net downward force measured by a scale, making the object appear to weigh less.
What is the difference between buoyancy and buoyant force?
Buoyancy is the tendency of an object to float or rise in a fluid. Buoyant force is the upward force exerted by the fluid that causes buoyancy. They describe the same phenomenon — buoyancy is the effect, buoyant force is the physical quantity measured in newtons.