FLUID PRESSURE Physical Science 9 th Jacqueline P. Hancock

What is a fluid? A substance that can easily flow and take the shape of its container –Liquids are fluids –Gases are fluids Viscosity (physical property) –The resistance of a fluid to flow

Fluid Pressure How does a fluid exert pressure on it’s container? The collisions of the tiny particles against the container cause a force –Pascal = 1 N/m 2 –N/cm 2 is used for smaller areas

Pascal’s Principle If there are no outside forces acting on a fluid, the pressure exerted by the fluid will be the same throughout and in all directions.

Hydraulics If a force is applied to the fluid, that force is transmitted through the fluid. Pressure is increased in all directions.

Hydraulic Devices Brakes in the car Shock absorbers Heavy equipment (front end loader or bulldozer)

Bernoulli’s Principle As the speed of a fluid increase; the pressure decreases Uses as a source of lift in flight –Example Spoon and running water demo

Creating Lift-Aerodynamics The air moves faster across the top of the wing Pressure is decreased over the top causing an unbalanced force. The wing is now pushed upward

SPOILER The air moves faster underneath the spoiler causing the pressure on top of the car to be greater

SPLITTER The barrier restricts the amount of air while it increases it’s flow. Causes a lower pressure under the car-less drag

Archimedes Greek philosopher and mathematician ( B.C.) Regarded as one of the greatest physical scientists of all time 2,000 years ago,while taking a bath, he discovered a method for figuring out whether the crown had been made of pure gold or a cheaper metal. Archimedes was so excited about his discovery, he ran straight from the tub through the streets shouting, "Eureka!" We now call his discovery Archimedes' Principle

Archimedes’ Principle

Buoyancy The ability of a fluid to exert an upward force on an object placed in it Opposed gravity Density and gravity are closely related

Opposite Forces When an object is submerged you have two main forces The downward force due to gravity(weight) The upward force due to buoyancy These forces will determine whether the object will sink or float

Floating Objects When the buoyant force is greater that the weight of the submerged object, the object will float at the surface of the fluid

Floating Objects When the buoyant force equals the weight of the submerged object, it floats beneath the surface

Floating Objects When the objects weight is greater than the buoyant force the object will not float

How can a boat float?

Density & Buoyancy Displaced water < ball weight Displaced water = hull weight