Apparent weight in fluid

Intermediate

True weight minus buoyancy.

Apparent weight = true weight − buoyancy. It's how Archimedes tested the king's crown.

Worked example

A 5 N object showing 3 N in water has F_b = 2 N, V = 2.04×10⁻⁴ m³.

Common mistake

Reading changes with the fluid.

In more detail

An object immersed in fluid appears lighter by the buoyant force. Its apparent weight is its true weight minus the weight of fluid displaced.

Measuring the density of a solid by weighing it in air and in water.
Scales in fluids use this principle to find relative densities.
A person weighs less in a swimming pool, because the buoyant force from the water reduces the net downward force.

How do I find density this way?

Use the ratio of the weight in air to the loss of weight in water.

Does apparent weight change with depth?

Not for a fully submerged object, since the displaced volume is constant.

How do I calculate apparent weight in a fluid?

Subtract the buoyant force, which is the weight of displaced fluid, from the object's true weight.