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http://www.physics.usyd.edu.au/teach_res/jp/fluids/wfluids.htm. http://www.physics.usyd.edu.au/teach_res/jp/fluids/. web notes: lect2.ppt pressure3.pdf pascal.pdf. Can you crush a steel can by pumping the air from the inside?. Solution Setup Force to collapse can F = p A
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http://www.physics.usyd.edu.au/teach_res/jp/fluids/wfluids.htmhttp://www.physics.usyd.edu.au/teach_res/jp/fluids/wfluids.htm http://www.physics.usyd.edu.au/teach_res/jp/fluids/ web notes: lect2.ppt pressure3.pdf pascal.pdf
Can you crush a steel can by pumping the air from the inside?
Solution Setup Force to collapse can F = p A Assume atmospheric pressure acts only on outside surface of can p = patm = 1.013105 Pa Need to know outside surface area A of can need to know dimension of can. Consider a cylinder of radius R = 0.15 m and height h = 0.30 m A = 2(R2) + 2R h Action F = (1.013105){(2)(0.15)2 + (2)(0.15)(0.30)} N F = 4.3105 N How big is this force? Consider a 70 kg person weight = 700 N force equivalent to the weight of > 61 people.
How do we breath – get the air in and out of our lungs? http://www.lung.ca/children/grades4_6/respiratory/how_we_breathe.html
D h A C B How can you measure the pressure of a gas? Manometer measures gauge pressure g h
What is a simple way to measure atmospheric pressure? A Mercury Barometer h patm patm B C r
How do you measure blood pressure? p = r g h
Pascal's Principle 1653 Blaise Pascal (1623 – 1662) Pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and walls of the containing vessel.
Tennis Ball Impact on Eye A blow to the eye by a tennis ball can cause more damage than one might expect because of the transmission of the pressure to the back of the eye http://hyperphysics.phy-astr.gsu.edu/hbase/pasc2.html
Hydraulic brakes http://hyperphysics.phy-astr.gsu.edu/hbase/pasc2.html
F2 F1 h1 oil h2 A1 A2
p1 = p2 F1 / A1 = F2 / A2 F2 = (A2 / A1) F1 A2 >> A1 F1 << F2 W1 = W2 F1 h1 = F2 h2 F1 h1 = (A2 / A1) F1 h1 h1 = (A2 / A1) h2 A2 >> A1 h1 >> h2 p = F / A W = F x