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FLUID PRESSURE. Or feeling a bit stressed lately???. Are you under a lot of pressure? Do you feel a lot of pressure?. PRESSURE! Right now, 1000 N of pressure are pushing on the top of your head!. What is pressure?. The result of a force distributed over an area Pressure = force = Newton
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FLUID PRESSURE Or feeling a bit stressed lately???
Are you under a lot of pressure?Do you feel a lot of pressure? PRESSURE! Right now, 1000 N of pressure are pushing on the top of your head!
What is pressure? • The result of a force distributed over an area • Pressure = force = Newton area meters2 • SI unit of pressure is the pascal (Pa) • 1 Pa = 1 newton/m2
Examples • If the area of a box touching the ground is 1.5 square meters, and its weight is 2700 newtons, what pressure does the box exert on the ground? • A gymnast standing on one hand (area 0.02 m2) pushes down on the ground with a force of 600 N. How much pressure does the gymnast exert on the ground?
So . …….. • The greater the area the force is distributed over, the less the pressure
For example: sharp knife vs dull knife • Sharp knife exerts a LARGE FORCE over a small area • FORCE/ area = PRESSURE • Dull knife exerts a small force over a LARGE AREA • Force/AREA = pressure
You do the math • Sharp knife: area = 1 mm2 • Dull knife: area = 5 mm2 • Force applied to each knife = 5 N Sharp knife = 5/1 = 5N/m2 Dull knife = 5/5 = 1N/m2
How about? Soft Bed vs. hard floor • Bed exerts force upward equal to your weight • Mattress exerts force upward over your whole body • Floor only pushes on pressure points which are touching the floor
Another example: Ice skating (or roller blading) • A shoe distributes the force (body weight) over a much larger area than the skate • So the skate exerts a much higher pressure on the ice than the shoe does • The skate pushes into the ice and • Voila! You can skate!
So what are fluids? • Substances that flow and have no definite shape • Examples: gases and liquids
Depth effects pressure As depth increases, water pressure increases (directly proportional)
Altitude effects pressure As altitude increase, air pressure decreases (inversely proportional)
Fluids want to . . . • Move from areas of high pressure to areas of low pressure • Everything wants to be equal
Standard atmospheric pressure = 14.7 pounds per square inch • What happened to this can?
Everything wants to be equal! • Pressure on the outside >>>> pressure on the inside • So when the can is heated, the can is crushed! • Why?????