Presentation on theme: "Pressure Pressure is a force exerted over an area on the surface"— Presentation transcript:
1 Pressure Pressure is a force exerted over an area on the surface of an object.Force and Pressure are not the same thing:Pressure decreases as the area over which a forceis applied increases.Pressure lessForceForcePressuregreater
2 Pressure = Force Area Units of pressure are Newtons/meter2 1 N/m2 = 1 pascal (Pa)
3 Pascal's PrincipleForceForceWhen a force is applied to a confined fluid, the changein pressure is transmitted equally to all parts of the fluid.
5 Pressure is caused by the movement of particles in the fluid. Every time they bump against the sideof the container they create pressure. The more bumpsthe more pressure.Fluid Particles
6 The more particles, the more pressure. The faster the particles move, the more pressure.Fluid Particles
7 Air Pressure Water Pressure Pressure caused by the weight of the air in the atmosphereas gravity pulls it down toward the center of the earth.Water PressurePressure caused by the weight of water as gravity pulls itdown toward the center of the earth.Remember, weight is a force.
8 Balanced PressureAir and water pressures press on objects from every direction.
9 If the pressure becomes unbalanced, the pressure of air or water can crush an object.The air pressure inside balances theair pressure outside the container.But if we take the air out of thecontainer, the outside pressurewill be far greater than inside andcrush the can.
10 Atmospheric Pressure and Elevation As your elevation increases, atmospheric pressure decreases.Water Pressure and DepthWater pressure increases as depth increases.
11 Buoyancy The force in liquids that acts opposite to gravity—it causes objects to feel lighter.Objects sink if their weight is greater than the buoyantforce acting on them.
12 Archimedes' Principle The buoyant force acting on a submerged object is equal tothe weight of the fluid theobject displaces.
13 Archimedes' Principle The buoyant force acting on the object equals the weight ofthe water displacedby the object.
15 DENSITY Density = Mass Volume If the density of an object is less than the density of water,the object will float.If the density of an object is greater than the density of water,the object will sink.
16 Pascal's PrincipleForceForceWhen a force is applied to a confined fluid, the changein pressure is transmitted equally to all parts of the fluid.
17 Hydraulic Systems Pressure of 10N/m2 Force = 10N/m2 x 10m2 100N Force 10m2 area1m2 areaPressure = 10N1m2Pressure of 10N/m2
18 Pressure Force Area ? 300N 20m2 15N/m2 15m2 3,000N/m2 150N 750N 7.5m2 How much pressure is produced by a 150N force actingover an area of 3m2?A 5N force is applied to a 5m2 piston in a hydraulic device.If the second piston has an area of 25m2, what is the forceproduced by this second piston?PressureForceArea?300N20m215N/m215m23,000N/m2150N750N7.5m2
19 Bernoulli's Principle so... The faster a fluid moves the less pressure the fluid exerts.so...As the speed of a moving fluid increases,the pressure within the fluid decreases.
20 Moving stream of wind (fluid) Smoke moves up chimney from high to Lower PressureMoving streamof wind (fluid)Smoke moves upchimney from high tolow pressure.
21 Wings are shaped so that air moves faster over the top of the wing thanunder the wing. This causes lower pressureabove the wing than below and creates lift so the plane can fly.