Fluid Forces Physical Science Mrs. Black Spring 2010.

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Fluid Forces Physical Science Mrs. Black Spring 2010

Pressure Force exerted over an area on a surface. Force exerted over an area on a surface. Pressure decreases as area increases. Pressure decreases as area increases. Pressure = Force Pressure = Force Area Area Fluid is material that can easily flow—liquid or gas. Atmospheric pressure decreases as altitude increases. Water pressure increases as depth increases.

Archimede’s Principle What causes an object to sink or float? What causes an object to sink or float? (Density labs: sink, float, submerged???) (Density labs: sink, float, submerged???) Bouyant force acting on a submerged object is equal to the weight of the fluid the object displaces. Bouyant force acting on a submerged object is equal to the weight of the fluid the object displaces. Float body in pool/bathtub; body displaces water; buoyant force is equal to weight of water displaced. Float body in pool/bathtub; body displaces water; buoyant force is equal to weight of water displaced. Shape and density impact… Shape and density impact…

Pascal’s Principle How does a hydraulic system work? How does a hydraulic system work? When force is applied to a confined fluid, the change in pressure is transmitted throughout the fluid. When force is applied to a confined fluid, the change in pressure is transmitted throughout the fluid. Demo: squeeze bottle… Demo: squeeze bottle… Mechanic shop---car lift Mechanic shop---car lift Car brakes… Car brakes… Glass/screen door on homes, car trunk or hatch… Glass/screen door on homes, car trunk or hatch…

Bernoulli’s Principle States that the faster a fluid moves the less pressure the fluid exerts. States that the faster a fluid moves the less pressure the fluid exerts. As the speed of a fluid increases the pressure within the fluid decreases. As the speed of a fluid increases the pressure within the fluid decreases. …huh?? …huh?? How does an airplane fly?...an atomizer work?...a flying disk (frisbee) move through the air? How does an airplane fly?...an atomizer work?...a flying disk (frisbee) move through the air?

Bernoulli…(cont.) Demo—hold a sheet of paper in front of your lips; blow over top of paper…what happens? Demo—hold a sheet of paper in front of your lips; blow over top of paper…what happens? Object design can impact ability to fly. The slanted design of an airplane wing produces lift. The slant causes the air hitting the wing to move downward—air exerts an equal and opposite (Newton??) force on the wing and pushes it upward. This upward force helps the airplane to take off. Object design can impact ability to fly. The slanted design of an airplane wing produces lift. The slant causes the air hitting the wing to move downward—air exerts an equal and opposite (Newton??) force on the wing and pushes it upward. This upward force helps the airplane to take off. Airplane wing designed to produce lift (upward force)—the curved shape of the wing causes air moving over top of wing to move faster than the air below the wing—as a result the air moving over the top exerts less pressure on the wing than the air moving below. The difference in pressure above and below the wing creates lift needed for plane to fly. Airplane wing designed to produce lift (upward force)—the curved shape of the wing causes air moving over top of wing to move faster than the air below the wing—as a result the air moving over the top exerts less pressure on the wing than the air moving below. The difference in pressure above and below the wing creates lift needed for plane to fly. (See pg 396 -397for atomizer, flying disk) (See pg 396 -397for atomizer, flying disk)

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