Physical Science 9 Chapter 16:Solids, Liquids, and Gases Section 16.2: Properties of Fluids

Buoyancy --Buoyancy is the ability of a fluid (gas or liquid) to exert an upward force on an object immersed in the fluid. --An object will float if its weight is less than the buoyant force the fluid exerts on the object. --An object will sink if its weight is more that the buoyant force the fluid exerts on the object.

--Archimedes’ principle says that the buoyant force on an object is equal to the weight of the fluid displaced by the object. --An object will float if its density is less than the density of the fluid it is placed in.

Pascal’s Principle --Pascal’s principle says that the pressure applied to a fluid is transmitted throughout the fluid. --Pressure is force per unit area. --Hydraulic machines use Pascal’s principle to lift heavy loads.

Bernoulli’s Principle --Bernoulli’s principle says that as the velocity of a fluid increases, the pressure exerted by the fluid decreases. --Bernoulli’s principle explains how airplanes that are heavier than air are able to fly.

--Because of the shape of an airplanes wing, air moves over the top of the wing faster that it moves along the bottom of the wing. --This produces a lower pressure on the top of the wing, producing an upward force called lift that keeps the airplane in the air as long as it keeps moving fast enough.

Viscosity --The viscosity of a liquid is the resistance of the liquid to flow. --The viscosity of a liquid is determined by the attractive forces between the molecules of a liquid. --Molecules with strong attractive forces have a higher viscosity. (ex: syrup, molasses) --The viscosity of a liquid decreases as the temperature of the liquid increases.