Pressure – The result of force distributed over an area – Pressure = Force(in Newton's – N)/area (m 2 ) Pascal (Pa) – SI unit for Pressure – Named after French scientist, Blaise Pascal (1623 – 1662) Pressure in Fluids – Fluid – substance that assumes the shape of its container Liquid and gas – Depth and type of fluid = 2 factors that affect pressure As depth increases, pressure increases – Pressure at 25 cm in bathtub and lake are the same » Amount doesn’t affect Pressure – The result of force distributed over an area – Pressure = Force(in Newton's – N)/area (m 2 ) Pascal (Pa) – SI unit for Pressure – Named after French scientist, Blaise Pascal (1623 – 1662) Pressure in Fluids – Fluid – substance that assumes the shape of its container Liquid and gas – Depth and type of fluid = 2 factors that affect pressure As depth increases, pressure increases – Pressure at 25 cm in bathtub and lake are the same » Amount doesn’t affect

Weight of Earth atmosphere at sea level = 101kPa – Air pressure increases with depth of atmosphere just like water – AS ALTITUDE INCREASES, AIR PRESSURE DECREASES – Why do your ears pop? Unbalanced air pressure inside and outside your ear b/c pressure changes more quickly than ears adjust – Pressure equalizes when air passes thru a small tube and you hear a pop – Body is not crushed by atmosphere b/c pressure inside your body balances outside pressure Weight of Earth atmosphere at sea level = 101kPa – Air pressure increases with depth of atmosphere just like water – AS ALTITUDE INCREASES, AIR PRESSURE DECREASES – Why do your ears pop? Unbalanced air pressure inside and outside your ear b/c pressure changes more quickly than ears adjust – Pressure equalizes when air passes thru a small tube and you hear a pop – Body is not crushed by atmosphere b/c pressure inside your body balances outside pressure

Transmitting Pressure in a Fluid 13.2 – Pascal’s Principle A change in pressure at any point in a fluid is transmitted equally and unchanged in all directions throughout the liquid – Hydraulic Systems Device that uses pressurized fluid acting on pistons of different sizes to change a force Input force applied to small piston, pushes on fluid of seal system  pushes large piston = output force Transmitting Pressure in a Fluid 13.2 – Pascal’s Principle A change in pressure at any point in a fluid is transmitted equally and unchanged in all directions throughout the liquid – Hydraulic Systems Device that uses pressurized fluid acting on pistons of different sizes to change a force Input force applied to small piston, pushes on fluid of seal system  pushes large piston = output force

Daniel Bernoulli (1700 – 1782) As speed of fluid increases, the pressure within fluid decreases – Blow across the top of a piece of paper, paper lifts upward… WHY? Pressure is constant below and decreases above Wings and Lift – Why can a bird and airplane fly Aerodynamics so air travels faster over the wings Lift – the pressure difference between the top and bottom of the wing creates and upward force Birds can flap wings to produce some lift and forward motion – Sometimes do opposite with cars to keep downward force for traction Daniel Bernoulli (1700 – 1782) As speed of fluid increases, the pressure within fluid decreases – Blow across the top of a piece of paper, paper lifts upward… WHY? Pressure is constant below and decreases above Wings and Lift – Why can a bird and airplane fly Aerodynamics so air travels faster over the wings Lift – the pressure difference between the top and bottom of the wing creates and upward force Birds can flap wings to produce some lift and forward motion – Sometimes do opposite with cars to keep downward force for traction

Buoyant Force – Buoyancy – the ability of a fluid to exert an upward force on an object lace in it – Apparent loss of weight Water exerts and upward force on object, making easier to lift – Acts in opposite direction of gravity – Water pressure increases with depth SO forces pushing up on bottom are greater than forces pushing down on top Buoyant Force – Buoyancy – the ability of a fluid to exert an upward force on an object lace in it – Apparent loss of weight Water exerts and upward force on object, making easier to lift – Acts in opposite direction of gravity – Water pressure increases with depth SO forces pushing up on bottom are greater than forces pushing down on top

Archimedes – Greek mathematician – died 212 B.C. The buoyant force on an object is equal to the weight of the fluid displaced by the object Archimedes – Greek mathematician – died 212 B.C. The buoyant force on an object is equal to the weight of the fluid displaced by the object

Density = mass/volume – g/cm 3 – If object less dense than fluid = float 2 forces always act on an object in a fluid – Weight Equals force of gravity (mass X 9.8 m/s 2 ) Acts downward – Buoyant force Equals weight of volume of displace fluid Acts upward – When force is equal – object floats or is suspended Density = mass/volume – g/cm 3 – If object less dense than fluid = float 2 forces always act on an object in a fluid – Weight Equals force of gravity (mass X 9.8 m/s 2 ) Acts downward – Buoyant force Equals weight of volume of displace fluid Acts upward – When force is equal – object floats or is suspended

Suspended – Same density as the fluid it is submerged in – Buoyancy = weight Sinking – weight > buoyancy Floating – Buoyancy > weight – Why does a piece of steel sink and a huge steel ship float? Ship – Shape of hull » Shaped to displace large volume of water = large buoyant force and it increases volume and decreases density Suspended – Same density as the fluid it is submerged in – Buoyancy = weight Sinking – weight > buoyancy Floating – Buoyancy > weight – Why does a piece of steel sink and a huge steel ship float? Ship – Shape of hull » Shaped to displace large volume of water = large buoyant force and it increases volume and decreases density

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