MULTIPLE-CHOICE PROLEMS:(Two marks per answer) (Circle the Letter eside the Most Correct Answer in the Questions elow.) 1. The absolute viscosity µ of a fluid is primarily a function of: a. Density. b. Velocity. c. Pressure. d. Temperature. e. None of the above.. An ideal fluid a. Is one which obeys Newton's Law of Viscosity. b. Has constant density and viscosity. c. Has zero viscosity and satisfies p = ρrt. d. Is incompressible and satisfies p = ρrt. e. Has zero viscosity and is incompressible. 3. A streamline is a. The line connecting the midpoints of the flow cross-sections. b. Defined only in uniform flow. c. Always fixed in space for steady flows. d. Drawn perpendicular to the velocity vector at each point in the flow. e. Always along the path of a particle. 4. The velocity field given by V x i xt j x t k is a. Three-dimensional and unsteady. b. One-dimensional and unsteady. c. One-dimensional and steady. d. Two-dimensional and unsteady. e. Three-dimensional and steady. 5. If a uniform solid body weighs 50 N in air and 30 N in water, its specific gravity is: a. 3.00 b..50 c. 1.67 d. 1.50 e. 1.5
6. Two parallel plates, one moving at 4 m/s and the other stationary, are separated by a 5- mm-thick layer of oil with specific gravity of 0.80 and kinematic viscosity 1.5E-4 m /s. What is the average shear stress in the oil? a. 160 Pa b. 15 Pa c. 100 Pa d. 80 Pa e. 60 Pa 7. Newton s law of viscosity relates a. The normal stress and rate angular deformation b. Shear stress, viscosity and temperature c. Intensity of pressure and rate of angular deformation d. Shear stress and rate of angular deformation e. Viscosity and rate of angular deformation 8. If the weight of a body immersed in a fluid exceeds the buoyant force, then the body will a. Float b. Flip over c. Tend to move downward and it may finally sink d. Rise until its weight equals the buoyant force e. None of the above 9. The location of the centre of pressure of the force caused by the liquid acting on a plane surface submerged in a liquid is a. Always above the centroid. b. Always at the centroid of the surface. c. At the centroid if the surface is horizontal. d. Independent of the inclination of the surface. e. Always below the centroid regardless of the value of the angle of the surface. 10. The horizontal component of the force acting on a submerged curved surface is equal to the a. Weight of the liquid displaced. b. Weight of the liquid vertically above the curved surface. c. Force on a projection of the curved surface on a vertical plane. d. Product of the pressure at the centroid and the curved surface area. e. Weight of the curved surface.
FILL IN THE LANKS: (One mark per blank) (Fill in the blanks with the most appropriate word/number or mathematical expression.) There are ten blanks to fill in. Each correct answer is worth one mark. 1. The shear stress τxy is directed in the Y coordinate direction and acts on the plane whose normal is in the X direction.. Reynolds number is the ratio of the inertia force to the VISCOUS force. 3. The buoyancy force that acts on a submerged body is the difference between the weight of fluid above the LOWER surface of the body and the weight of fluid above the UPPER surface of the body. 4. The buoyant force has a magnitude equal to the weight of the fluid DISPLACED by the body and is directed vertically UPWARDS 5. A fluid is a substance that deforms CONTINUOUSLY when subjected to a shear stress no matter how SMALL that shear stress may be. 6. A STREAKLINE is a line joining the present location of all particles that have passed a given point. TRUE AND FALSE QUESTIONS: (One and one-half marks per answer) (Circle the correct response, TRUE or FALSE) 1. If a perfect gas undergoes an isothermal process, the relationship between pressure and density is P = constant *ρ (TRUE/FALSE).. Random molecular motion makes a more important contribution to the viscosity of a gas than intermolecular cohesion (TRUE/FALSE). 3. In unsteady flows, streamlines show which fluid particles have passed through a given point (TRUE/FALSE). 4. Viscosity is not important in a study of a fluid body at rest (TRUE/FALSE). 5. For the continuum assumption to be valid the Knudsen number must be very small (TRUE/FALSE). 6. Turbulent flow generally occurs for cases involving very slow motions of very viscous fluids in very small diameter tubes (TRUE/FALSE). 7. Shear stresses are not important within the boundary layer (TRUE/FALSE). 8. The Lagrangian Method is concerned with a region or a point in space (TRUE/FALSE). 9. Pipe flows are always laminar if the Reynolds number is less than 000 (TRUE/FALSE). 10. The viscosity of water at 0ᴼC is 1.00x10-3 kg / (m sec) (TRUE/FALSE).
SHORT NUMERICAL PROLEMS: (Answer these problems in the space allotted.) 1. Determine the value of (PA - P) in Pa. Where: h1 = 0 cm h = 10 cm h3 = 15 cm h4 = 10 cm (0 Marks) g = 9.81 m/s P Am = P m The Line of common pressure in the manometer U is Am m. Therefore, for constant density liquids: From table: = 680 kg/m 3 gasoline = 998 kg/m 3 HO = 13,550 kg/m 3 Hg P P h h h Am A 4 gasoline HO 3 Hg P P h m 1 gasoline A 1 gasoline 4 gasoline HO 3 Hg A 1 gasoline 4 gasoline HO 3 Hg A 1 4 gasoline HO 3 Hg and 0 P P h h h h P P h h h h P P ( h h ) h h (0.0 0.10) g 0. 10 g 0.15 g gasoline HO 0.10 680 0.10 998 0.1513,550 9.81 68 99.8 03.5 9.81 1584.0 1.6 kpa Hg
The tank shown in the figure below has a hemispherical dome of 1 m radius as part of its top surface. The tank is completely closed and contains pressurized water at 0ᴼC. A pressure gage is located on the top surface as shown and has a reading of 50 kpa gage pressure. Determine the net horizontal and vertical components of the force that the water on the inside and the air on the outside exert on just the dome portion of the top. (0 Marks) As the pressure gauge registers gauge pressure, the air pressure contribution on the inside of the tank is cancelled by the air pressure on the outside of the tank. As it is a hemispherical dome, the net horizontal component of the force applied by the pressurized water is zero since the dome is symmetric. The net vertical force applied by the pressurized water can be determined by finding the net vertical force created by a column of water of height so as to create a hydrostatic force equal to 50 kpa at the top of the tank. Or, 50000 g h HO 998 9.81 h or h = 5.54 m. Using 3 HO 998 kg/m from table The total vertical force will be equal to the weight of water that would fill a column of that height with a diameter of metres plus the weight of water that would fill the inside of the hemisphere. F V HO gv T Thus, the total volume of water is Total Volume Volume of Cylinder + Volume of hemisphere 3 VT R h R /3 80.36.094 8.33 m 3 Then the vertical force applied by the water on the dome = V T * ρ g = 8.33 * 998 * 9.81 F v = 806049 Newtons = 806 kn in the upward direction.