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## Forces in Fluids

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**Forces in Fluids**Chapter 13**What is pressure?**• The result of a force acting over a given area. • Pressure = Force/Area • What label? • N/m2 • 1 N/m2 is known as a pascal (Pa)**Blaise Pascal**• 1623-1662 • French physicist and mathematician • Performed some of the first experiments dealing with pressure**Fluid pressure**• Fluids: a substance that attains the shape of its container. Examples: both liquids and gases. • Fluid pressure changes with depth in a column of water and with altitude. • Fluid pressure in water does not depend on the volume or weight only the depth.**Air Pressure**• Air pressure at sea level is approx. 101 kPa. • Air pressure will decrease with increases in altitude. • Examples: flying in a plane, driving in the mountains**Pascal’s Principle**• A change in pressure at any point in a fluid is transmitted equally and unchanged in all directions throughout the fluid**hydraulics**• Uses Pascal’s principle and moving pistons with an enclosed pressurized fluid: • Examples: • Car brakes, jacks, and loaders**Problem:**• If a force of 30 N is placed on a small piston of a hydraulic device with an area of 2 cm2, what size of a load can the larger piston lift if the area of the larger piston is 80 cm2?**Bernoulli’s principle**• Swiss scientist • 1700-1782 • Explained the basis behind airplane flight. • As the speed of a fluid increase, the pressure decreases**buoyancy**• The ability of a fluid to exert an upward force on an object resulting in an APPARENT loss of weight of the object**Archimedes**• Greek mathematician • 287-212 B.C. • Best known for his theory that the buoyant force on an object is equal to the weight of the fluid displaced**Application of buoyancy**• Ballast tanks in submarines**Assignment:**• Pages 407-408 • 1-10, 12, 15, 17, 20, 26, 27 • Page 409 • 1-6