Buoyancy, Density, and Water

Principles of Fluids Overview: Archimedes’ Principle Pascal’s Principle Bernoulli’s Principle Boyle’s Law

Density is the mass of a substance per unit volume (usually measured in grams per milliliters, g/ml). Buoyancy is the upward force that a fluid exerts on an object less dense than itself.

Q: How do ships float?

A: A greater force is pushing up on the ship than the weight force pushing down. This supportive force is called buoyant force.

If the buoyant force is equal to the object’s weight, it will float.

If the buoyant force is less than the object’s weight, it will sink.

Bouyant force was explained by Archimedes and it became known as Archimedes’ Principle. Archimedes was a Greek mathematician who lived around the 3rd century B.C.

Archimedes’ Principle states that an objects weight will cause the object to sink while at the same time displacing the fluid.

If the weight of the water displaced becomes equal to weight of the object, it floats.

If the weight of the water displaced becomes less than the weight of the object, it sinks.

Q: Why is this principle important?

A: Properties of fluids ultimately determine the design of ships, airplanes, cars, and hydraulic machines.