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COOP_4 10 - (b Express the magnitude of the drag force D...

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Name: ______________________________Section/Instr.: ___________________ Partners: __________________________________________________________ Physics 2207, Fall 2010 1 Cornell University Cooperative Problems 4: Friction and Drag Forces 1. The magnitude of the force on an object due to turbulent drag as it moves through a fluid (or as a fluid moves past it) is 2 2 1 v A C D . While hiking, you come to a swiftly moving stream that appears to be roughly 1.0 m deep (i.e., about the length of your legs). You estimate the coefficient of static friction between your hiking boots and the rocks in the bottom of the stream to be 50 . 0 s . (a) Draw a carefully labeled free-body diagram (FBD) showing all the forces that would act on you if you were to stand in the stream. Near (but not in) your FBD draw an arrow to represent the direction of flow of the water.
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Unformatted text preview: (b) Express the magnitude of the drag force D that would be exerted on you by the flowing water as a function of its speed v . Assume that the water density is 3 w kg/m 1000 , and that your legs can be modeled as cylinders which have a drag coefficient 2 . 1 C . (Hint: What is the effective area A of your legs? You may need to make some estimates here.) (c) What force would be exerted on you if the water flowed at 10 m/s (about 22 mi/h)? (d) What is the maximum value of the magnitude of the frictional force, max s, f , between your boots and the rocks? (Use your own mass.) (e) What is the maximum drag force magnitude max D that you can experience and not lose your grip on the rocks on the bottom of the stream? To what water speed v does this correspond?...
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