Presentation on theme: "Fluid Fluid - any substance that flows… liquids and gases. Ex. Water and Air."— Presentation transcript:
Fluid Fluid - any substance that flows… liquids and gases. Ex. Water and Air
Pressure - force per unit of area. A force that exist in fluids are caused by the mass and motion of the particles making up the fluid. Fluid Pressure
Calculate Fluid Pressure P = ρ · g · h Units: N/m 2 or Pa Air pressure at sea level is 14.7 psi = 760 mm Hg = 101 kPa = 1 atm. ρ of H 2 O is 1000 kg/m 3
What is the pressure due to water 3.0 m below the surface of a lake? A truck falls through the too thin ice at Lake Poinsett, and sinks 7 m to the bottom. –What is the pressure on the truck at this depth? –If the area of one of the doors on the truck is 0.7 m 2, calculate the force that the water exerts on it. Calculate Fluid Pressure
Fluid pressure acts in all directions. Force of gravity causes the pressures in a fluid to vary with depth only. Not with horizontal position. Fluids will move from areas of high pressure to areas of low pressure. Properties of Pressure
Hydraulics Pascals Principle - pressure is transmitted equally throughout a confined liquid. Multiplies force! Ex. Brakes, hydraulic lifts, etc.
Calculate Hydraulics P = F 1 = F 2 The small piston of a hydraulic lift has a cross sectional area of 3 cm 2, and the large piston has an area of 200 cm 2. What force must be applied to the small piston to raise a load of 15,000 N? A1A1 A2A2
Buoyancy The upward force exerted by a fluid on a substance partly or completely immersed in it. F b < wt. of sub. SINK F b wt. of sub. FLOAT!
Weight Difference method ~ F b = Dry weight – Wet weight Weight of displaced water ~ F b = ρ · g · v Calculate Buoyant Force
Archimedes Principle Archimedes Principle - The buoyant force acting in a substance in a fluid at rest is equal to the weight of the fluid displaced by the substance. F b = weight of displaced fluid or F b = ρ · g · v
Sink or Float? Density (object)> Density (fluid) SINKS Density (object) Density (fluid) FLOATS
Bernoullis Principle For a fluid undergoing steady flow, the pressure is lower where the fluid is flowing faster. Ex. Shower curtain, airplane wing, etc.