Fluids and Buoyancy. 1. What will happen to the scale reading as the mass is lowered?

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1 Fluids and Buoyancy. Wat will appen to te scale reading as te mass is lowered? M Using rcimedes Principle: any body fully or partially submerged in a fluid is buoyed up by a force equal to te weigt of te fluid displaced. If mass is more dense tan fluid, mass will sink and scale will read weigt of fluid and full weigt off mass. If mass is less dense tan fluid, object will float and scale will increase until equilibrium is reaced between buoyancy and weigt of mass.. Find pressure as a function of time. ime t 0, te water level is feet. Cross-sectional area is 8 ft for te top and ft for te bottom. M - t ft ft M t Container wit cross sectional area perpendicular to y-axis of 6-y/. Wat is pressure at bottom? Rate of water addition is (-t) ft /min and leaves continuously a ft /min.

2 P ρg dv d dt ( t) t dt dv 6 d (6 ) dt ( ) t t dt 6 t + c 4 c?; t 0, ; c; c 6 + ( + t ) 0 4 ± t 0, P( t) ρg( 6 t t t + + ). For a ydrofoil aircraft, wy is turbulent flow preferable? Te indentations create turbulence in te boundary layer downstream of te indentations, canging te caracteristics of te flowing fluid to a turbulent boundary layer aead of te normal point of separation of te fluid from te foil, tis causing te fluid to cling close to te surface of te foil and postpone or delay trailing edge separation of te fluid stream from te foil. Te noise level is reduced, te performance and efficiency of te foil is improved, or boe noise level is reduced and te performance and efficiency of te foil is improved. 4. In te following simplified system, were is pressure te greatest? Heat Dissipater Condenser Heat Engine Pump

3 Higest pressure is downstream of te pump (counterclockwise rotation). 5. If te flow rate is increased by a factor of tree, ow does te pressure cange at bot points? Pressure will decrease by a factor of nine. Bernoulli's equation states tat, in a streamline fluid flow, te greater te speed of te flow, te less te static pressure, and te less te speed of te flow, te greater te static pressure. Tere exists a simple excange between te dynamic and static pressures suc taeir total remains te same. s one increases, te oter must decrease. Use te relationsip: (½)ρV + P P t 6. Wat is force F? F ft 9000 lbs Cross-sectional areas 9 in B 900 in B ssume at fluid is water 0 degrees Celsius and at sea level, terefore ρ water 0.07lbf/in lbf 0.07 in 9in F + in 9in 9in 9000lbf 0.07lbf F 9in ( 900in in F 86lbf 9000lbf 900in in) 7. ball of diameter 0 cm and mass 0 grams is dropped in a container of water. Te cross-sectional area of te container is 00 cm. Wat is te cange in te eigt of te water column? ssume cross-sectional area of te container is constant and temperature is 0 deg C. Density of ball:

4 ρ 0g ball.09g / 4 0 π cm ρ ball <ρ water, so te ball floats. So te weigt of te water displaced is 0g. Volume of water displaced: 0g V m / ρ 0cm g cm V V0 V0 Δ 0 + 0cm V 0 0cm 8. Te cross-sectional area of te sipon tube is constant. Te fluid flows from tub to tub. Determine te maximum eigt tat will still result in fluid flow. Tub Tub Maximum eigt of a sipon is (using Bernoulli s equation), and velocity of sipon is as slow as possible. max P atm ρg 9. Te motor on a centrifugal pump is ooked up backwards, causing te impeller to spin te wrong direction. Wat will appen to te ead vs. gpm curve? Wile flow would continue in te proper direction te efficiency of te pump would decrease. Te ead vs. gpm curve would decrease. 0. Describe ow a Venturi meter works and sow ow it can be used to calculate fluid flow (Bernoulli s Eqn. and te Continuity Eqn.) Venturi meter utilizes a nozzle to measure te mass flow rate of a fluid by measuring te differential pressure. Energy equation

5 q w Δgpe + Δppe + Δke ( P ( v v ) / ( P P ) / ρ + ( v Continuity Equation: P ) / ρ m! v v! /! Substitute: (( f c ) venturi m ; v m/ ( P P ) ( ) ) f ρ ρ P P P P v ) /. Wat appens to te water level wit respeco te sore wen te sailor trows te lead ancor overboard? Use rcimedes Principle: were an object partly or wolly immersed in a fluid is buoyed up by a force equal to te weigt of te fluid displaced..4 lead Va ( ) Va ( ). 4 water ρ ρ V a Terefore, ancor is displacing an amount equal to its volume..4v a reducing water level.. How far will te water soot out? d Energy Balance

6 E p E k v mg v g v t v t d v d 0 g gt + / g axt t + ( g )( / g ). Explain ow you would estimate te flow rate in a pipe. Measure flow in cfs. If water is dropping from a pipe you can measure wit carpenter s ruler. Measure orizontal distance, te vertical drop y. Cross section of a pipe: Flow ratearea*velocity*rougness factor (least accurate +/-0%) Timed volume using bucket and stopwatc: flow ratevolume/time 4. If te liquid is flowing in te direction indicated, at wat point is te pressure greatest? B C D E 5. Given a fluid flowing troug a pipe in te direction indicated, wat difference in parameters exists between points and B? B Pressure is lower as point B tan point due to energy losses in te pipe (ead loss. Te energy is converted to eat. 6. Wat is meant by laminar and turbulent flow? If you ad a piping system, wic type of flow would be better and wy?

7 Laminar flow is a fluid flow caracterized by non-turbulent and inefficient eat transfer capability. Turbulent flow as a great deal of mixing and friction. Laminar flow is more desired in piping because pump power is reduced due to te lower ead loss. Turbulent flow is desirable wen earansfer needs to be maximized. 7. Wic will raise te water level in a tank iger wen added a one pound block of iron or a one pound block of wood? rcimedes Principle Equation Wood displaces more volume of water tan lead