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Unformatted text preview: Fluid mechanics Fluid is matter that flows under influence of external forces (?) Fluids flow under shear! While solids experience some finite deformation. Do Newtons laws apply in fluid mechanics? Of course they do, since they apply everywhere unless the things get relativistic or quantum. What is the problem with the fluid mechanics then? Why do not we study it together with the regular mechanics? The trouble is we have got to deal with a continuumE where the notion of a body is difficult to define and it is not always straightforward where the forces come from. What do we do? For appropriate description of continuum mechanics we have got to introduce new notions and parameters. Density measures the mass per unit volume. SI units are kg/m 3 ] kg/m [ / 3 V m = There are compressible and incompressible fluids (nearly fixed vs. variable density). Pressure measures the normal force per unit area exerted by a fluid. SI units are N/m 2 or Pa, Pascal. Pa ], N/m [ 2 dA dF A F P = = Abrahams tank mosquito Mass 63 tons ( 63,000 kg) Caterpillar area 6 m 2 Ground pressure: atm 1 Pa 10 m 6 m/s 8 . 9 kg 000 , 63 5 2 2 = = = = = = A mg A F P Proboscis about 0.1 mm in diameter. Pressure of 10 5 Pa corresponds to N 10 8 4 / ) m 10 ( 14 . 3 Pa 10 4 / 4 2 4 5 2 = = = = = d P A P F Equivalent mass is g 0.1 kg 10 / 4 = = g F m Abrahams tank A mosquito weighs about 2 mg, 0.002 g....
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This note was uploaded on 12/13/2011 for the course PHYS 2C PHYS 2C taught by Professor Groisman during the Spring '11 term at UCSD.
 Spring '11
 groisman

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