Post on 27-Mar-2015
Pressure is a force exerted over an area on the surfaceof an object.
Force and Pressure are not the same thing:Pressure decreases as the area over which a forceis applied increases.
Force Pressuregreater
ForcePressure less
Units of pressure are Newtons/meter2
1 N/m2 = 1 pascal (Pa)
ForceForce
When a force is applied to a confined fluid, the change in pressure is transmitted equally to all parts of the fluid.
Cartesian Diver
Pressure increasedPressure decreased
Fluid Particles
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
The more particles, the more pressure. The faster the particles move, the more pressure.
Pressure caused by the weight of the air in the atmosphereas gravity pulls it down toward the center of the earth.
Pressure caused by the weight of water as gravity pulls it down toward the center of the earth.
Remember, weight is a force.
Air and water pressures press on objects from every direction.
If the pressure becomes unbalanced, the pressure of airor water can crush an object.
The air pressure inside balances the air pressure outside the container.
But if we take the air out of the container, the outside pressure will be far greater than inside and crush the can.
As your elevation increases, atmospheric pressure decreases.
Water pressure increases as depth increases.
The force in liquids that acts opposite to gravity—itcauses objects to feel lighter.
Objects sink if their weight is greater than the buoyantforce acting on them.
The buoyant force acting on a submerged object is equal to the weight of the fluid the object displaces.
The buoyant force acting on theobject
equals the weight of the water displacedby the object.
Weight
Buoyant Force
Weight
Buoyant Force
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.
ForceForce
When a force is applied to a confined fluid, the change in pressure is transmitted equally to all parts of the fluid.
10N Force
1m2 area
Pressure of 10N/m2
100N Force
10m2 area
Pressure = 10N 1m2
Force = 10N/m2 x 10m2
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?
Pressure Force Area
? 300N 20m2
15N/m2 ? 15m2
3,000N/m2 150N ?
? 750N 7.5m2
The faster a fluid moves
the less pressure the fluid exerts.
As the speed of a moving fluid increases, the pressure within the fluid decreases.
Moving streamof wind (fluid)
Lower Pressure
Smoke moves up chimney from high to low pressure.
Wings are shaped so that air movesfaster over the top of the wing than under the wing. This causes lower pressureabove the wing than below and creates lift so the plane can fly.