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SP2011_Test1_Sols - 22.381 Undergraduate Mechanical...

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22.381 Undergraduate Mechanical Engineering – Fluid Mechanics Test 1 :Chapter 1 and 2 Instructor : Prof. D. Willis Name and UMS ID: 1. (35 pts) Concept Questions: Please answer the following concept questions fully, but concisely. Expla- nations for any questions are recommended if you are unsure of your answer. (a) True or False: Liquid viscosity generally decreases as the temperature rises True: As temperature rises, liquids in general become less viscous (b) True or False: Wetting liquids have higher surface tension than non-wetting liquids False: The ’wetting’ or ’non-wetting’ is a property of the material the fluid droplet is in contact with. Eg. Water and a waxed car, vs. water and metal. (c) True or False: Helium has negative weight, this is why helium balloons rise False: The reason is there is a buoyancy force greater than the weight of the helium and balloon (d) True or false: The only place in a fluid where shear stresses exist is at the walls of the flow. False: Shear stresses may occur anywhere in the flow (e) What is the difference between a Newtonian and Non-Newtonian Fluid? Give an example of each. Newtonian Fluids are special in that the stress-strain rate relationship is linear and has a zero intercept. Non-Newtonian fluids have nonlinear stress-strain rate relationships
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