phys124s11-l03

# Phys124s11-l03 - Physi cs 124 Spr i ng 2011 Lecture 2 Summary x cm m Weight acts at CM = C of G dx x r = ycm m dy y r = Static Equilibrium if

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1 Physi cs 124, Spr i ng 2011 Lecture 2 Summary 1/29/2010 Lecture 3 Fluids 2/4/2010 Outline Static Equilibrium if F external = 0, and external = 0 Weight acts at CM = CofG Stress strain smalldeformations L L = F AY V V =− P B x h =− F AS x cm = dx x  r m y cm = dy y  r m Pascal Archimedes Continuity Bernoulli Toricelli

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2 Physi cs 124, Spr i ng 2011 Basics P atm = 1.013x10 5 Pa = 1.013x10 5 N / m 2 = 1 atm = ... Fluid: liquid or gas Gases are highly compressible; liquids are not Approximate: density / volume constant Putting an object in a fluid leads to: Pressure force, a force per unit area perpendicular to a face A viscous (drag / frictional) force, parallel to a face Generally ignored in what follows P = F A Gauge pressure: Pressure relative to atmosphere Be aware: absolute pressure vs. Gauge pressure
3 Physi cs 124, Spr i ng 2011 Pascal's Principle A pressure applied to a liquid is transmitted undiminished to every point of the liquid and to the walls of the container Force L on Area L F R on A R Ignore effects of gravity for now. a: to left as larger pressure there For hydraulic lift in garage, car goes . .. b: to right as larger pressure there c: to left as larger force there d: to right as larger force there e: both sides are equally good A L A R

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4 Physi cs 124, Spr i ng 2011 Pascal's Principle A pressure applied to a liquid is transmitted undiminished to every point of the liquid and to the walls of the container For hydraulic lift in garage, car goes . .. Force 1 on Area 1 F 2 on A 2 Ignore effects of gravity for now. Pascal: P = F 1 A 1 = F 2 A 2 If A 2 A 1 , then F 2 F 1 A small force on left can support a big car on right.
5 Physi cs 124, Spr i ng 2011 Variation of Pressure with Depth Fluid in a gravitational field has weight. Each element of fluid supports the fluid above it. Pressure increases with depth. Consider a volume of fluid made out of smaller volumes; one is shown. P top F vertical = 0 P top A mg P bottom A = 0 Use m =  Ah, and divide out A to obtain: P bottom h P bottom = P top  gh Height h, area of top and bottom A, density , and pressure P top P bottom at top bottom or: P  gh = constant Ignoring gravity: not a good idea Pressure only depends on depth

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Physi cs 124, Spr i ng 2011 Example: water pressure P top P bottom h e: none of the above d: narrow slanted a: wide vertical c:bulging vertical b: curly vertical In which tube will the water go highest? And the demo answer is.
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## This note was uploaded on 03/24/2011 for the course PHYSICS 123 taught by Professor Madey during the Fall '08 term at Rutgers.

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Phys124s11-l03 - Physi cs 124 Spr i ng 2011 Lecture 2 Summary x cm m Weight acts at CM = C of G dx x r = ycm m dy y r = Static Equilibrium if

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