Immersed Weight Calculator
Find an object's apparent weight when submerged.
Submerged objects feel lighter because buoyancy supports part of their weight.
How the Math Works
The Immersed Weight Calculator uses Archimedes' principle to determine an object's apparent weight when submerged in a fluid. The formula W_app = m·g − ρ_fluid·g·V combines the object's actual weight (m·g) with the buoyant force (ρ_fluid·g·V), which equals the weight of displaced fluid. Here, m is mass in kilograms, g is gravitational acceleration (9.81 m/s³), ρ_fluid is fluid density in kg/m³, and V is the object's volume in m³. The calculator subtracts the upward buoyant force from the downward gravitational force to reveal the reduced weight experienced underwater.
Practical Applications
To apply this calculation, first measure or determine the object's mass and volume. For irregular objects, submerge them in water and measure the displaced volume. Identify the fluid's density (fresh water = 1000 kg/m³, salt water ≈ 1025 kg/m³). Multiply each variable by gravitational acceleration, then subtract the buoyant force term from the weight term. This calculation is essential for engineering projects involving submerged structures, maritime operations, or determining whether objects will float or sink in different fluids.
Day-to-Day Use
Understanding immersed weight helps explain everyday phenomena like why ocean divers feel lighter underwater or why it's harder to push a water-filled bucket overhead compared to an empty one. The calculator aids in practical tasks such as determining if your kayak will float with your gear, calculating how much a swimming pool ladder will feel when fully submerged, or understanding why we can more easily lift heavy objects underwater during activities like salvage operations or scientific research.
Worked example
5 kg, 0.002 m³ object in water → about 29.4 N (down from 49.1 N).
FAQ
When does it float?
When buoyancy meets or exceeds the weight, giving zero or negative apparent weight.