Properties of Fluids

Fluids and Buoyancy What is a fluid? A fluid can be a liquid or a gas. Buoyancy is the ability of a fluid to exert an upward of force on an object immersed in it. If the buoyant force is equal to the objects weight, it will float. If the buoyant force is less than the weight, the object will sink.

Archimedes’ Principle Archimedes was a Greek mathematician who lived in the 3rd century B.C. He found that the buoyant force on an object is equal to the weight of the fluid displaced by the object.

Density Would a steel block that was the same size as a wood block float in water? No, because they have different densities. If two objects are the same size, the heaviest one would be more dense. Density = mass/volume D = m/v The unit is grams per cubic centimeter or g/cm3.

Pascal’s Principle Blaise Pascal (1623-1662) was a French scientist who discovered a useful property of fluids. He found that pressure applied to a fluid is transmitted throughout the fluid. Pressure is force exerted per unit area.

Bernoulli’s Principle Daniel Bernoulli (1700-1782) was a Swiss scientist who studied the properties of moving fluids such as water and air. He found that as velocity of a fluid increases, the pressure exerted by the fluid decreases.

Viscosity Another property of fluids is the tendency to flow. A resistance to flow by a fluid is called viscosity. Water would have a low viscosity, syrup would have a high viscosity.