Buoyancy and Density Fluid  matter that flows  liquids and gases Buoyancy  The ability of a fluid to exert an upward force on an object immersed in it  Acts opposite to gravity  Buoyant force

Archimedes Principle Buoyancy results in the apparent loss of weight of an object in a fluid

Archimedes’ Principle Buoyant Force  upward force exerted by a fluid on an immersed object  buoyant force > weight  buoyant force = weight  buoyant force < weight balloon rises balloon sinks balloon floats

More water needs to be displaced in order to cancel weight  ball floats lower in the water. Not enough water is displaced in order to cancel weight  ball sinks. Archimedes’ Principle  the buoyant force on an object in a fluid is equal to the weight of fluid displaced by the object Very little water needs to be displaced in order to cancel weight  ball floats on surface. View animationsView animations produced by students at Poly Prep Country Day School in Brooklyn, New York. View Buoyancy JAVA Applet.

Density and Buoyancy If an object is less dense than the fluid it is in, it will float. If the object is more dense it will sink Different fluids can also float or sink in one another

Suspended An object that has the same density as the fluid it is submerged in will be suspended  It will float at any level in the fluid  Buoyant force acting on the object exactly equals the objects weight

Sinking When the ships weight becomes greater than the buoyant force acting on it, the ship will sink As the water enters, the ship displaces less water and the buoyant force decreases

Floating A heavy steel ship floats because of the shape of the hull Is shaped to displace a large amount of water creating a large buoyant force Objects float easier in dense fluids

Forces and Pressure in Fluids Forces and Pressure in Fluids Transmitting Pressure in a Fluid Fluid exerts pressure equally in all directions at a given depth Amount of pressure exerted by a fluid depends on the type of fluid and its depth

Pascal’s Principle  pressure applied to a fluid is transmitted unchanged throughout the fluid View hydraulics explanation.

Hydraulic Systems Science of applying Pascal’s principle Is a device that uses pressurized fluid acting on pistons of different sizes to change a force

Hydraulic Systems An increased output force is produced because a constant fluid pressure is exerted on the larger area of the output piston If a large piston had 8 times the area of a small piston, then it will have an output force 8 times greater than the input force, ex: pg 395

Hydraulic Systems Why is this??? Recall that Force is = to Pressure x Area Because the pressure on each piston is the same, the difference in forces is directly related to the difference in areas

Pascal’s Principle The area of an output piston is 25 times greater than the area of the input piston. If the input force is 40 newtons, what is the output force? 40 newtons x 25 = 1000 N

Bernoulli’s Principle  as the velocity of a fluid increases, the pressure exerted by the fluid decreases  EX: airplane lift, curve balls

Wings and Lift Air travels faster over the top of the wings than underneath This creates a low pressure area above the wing The difference in pressure creates lift

Wings Sometimes wings are used to create a downward force Race cars often have an upside down wing called a spoiler mounted on the back This pushes the car down giving it better traction

Bernoulli’s Principle Venturi Effect  fluids flow faster through narrow spaces causing reduced pressure  EX: garden sprayer

Spray Bottles Water moves through the sprayer at high speed causing low pressure Water and fertilizer mix Mixture sprays out, EX: pg 397 figure 9

Bernoulli’s Principle Airplane liftCurve Ball View airplane wings explanation.airplane wings explanation