Fluid Mechanics Take Home Test Honors

Name ______Date ______

Fluid Mechanics Take Home Test – Honors

Multiple Choice Identify the choice that best completes the statement or answers the question.

____ 1. Which of the following statements is NOT correct? a. A fluid flows. b. A fluid has a definite shape. c. Molecules of a fluid are free to move past each other. d. A fluid changes its shape easily. ____ 2. A table-tennis ball has an average density of 0.084 g/cm3 and a diameter of 3.8 cm. What force can submerge 3 the ball in water? (w = 1.00 g/cm ) a. 1.0 N c. 0.52 N b. 0.79 N d. 0.26 N ____ 3. A cube of wood with a density of 0.780 g/cm3 is 10.0 cm on each side. When the cube is placed in water, 3 what buoyant force acts on the wood? (w = 1.00 g/cm ) a. 7.65  103 N c. 7.65 N b. 5.00 N d. 6.40 N ____ 4. Because a buoyant force acts in the opposite direction of gravity, a. objects submerged in water have a net force smaller than their weight. b. objects submerged in water have a net force larger than their weight. c. objects submerged in water have a net force equal to their weight. d. objects submerged in water appear to weigh more than they do in air. ____ 5. Which of the following statements about floating objects is correct? a. The object’s density is greater than the density of the fluid on which it floats. b. The object’s density is equal to the density of the fluid on which it floats. c. The displaced volume of fluid is greater than the volume of the object. d. The buoyant force equals the object’s weight. ____ 6. Which of the following statements about completely submerged objects resting on the ocean bottom is correct? a. The buoyant force acting on the object is equal to the object’s weight. b. The apparent weight of the object depends on the object’s density. c. The displaced volume of fluid is greater than the volume of the object. d. The weight of the object and the buoyant force are equal and opposite. ____ 7. A water bed that is 1.5 m wide and 2.5 m long weighs 1055 N. Assuming the entire lower surface of the bed is in contact with the floor, what is the pressure the bed exerts on the floor? a. 250 Pa c. 270 Pa b. 260 Pa d. 280 Pa ____ 8. Each tire of an automobile has an area of 0.026 m2 in contact with the ground. The weight of the automobile is 2.6  104 N. What is the pressure in the tires? a. 3.1  106 Pa c. 2.5  105 Pa b. 6.5  103 Pa d. 1.0  106 Pa ____ 9. How much pressure is exerted on a submarine at a depth of 8.50 km in the Pacific Ocean? (The density of sea water = 1.025  103 kg/m3, and the atmospheric pressure at sea level = 1.01  105 Pa.) a. 8.6  105 Pa c. 8.7  106 Pa b. 9.5  106 Pa d. 8.6  106 Pa ____ 10. An ideal fluid flows through a pipe made of two sections with diameters of 1.0 cm and 3.0 cm, respectively. By what factor would you have to multiply the velocity of the liquid flowing through the 1.0 cm section to obtain the velocity of liquid flowing through the 3.0 cm section? a. 6.0 c. b. 9.0 d.

____ 11. A water tunnel has a circular cross section where the diameter diminishes from 3.6 m to 1.2 m. If the velocity of water flow is 3.0 m/s in the larger part of the tunnel, what is the velocity of flow in the smaller part of the tunnel? a. 9.0 m/s c. 27 m/s b. 18 m/s d. 54 m/s ____ 12. Water flows into a house at a velocity of 15 m/s through a pipe that has a radius of 0.40 m. The water then flows through a smaller pipe at a velocity of 45 m/s. What is the radius of the smaller pipe? a. 0.53 m c. 0.17 m b. 0.23 m d. 0.37 m ____ 13. Which of the following is not an example of laminar flow? a. a river moving slowly in a straight line b. smoke rising upward in a smooth column through air c. water flowing evenly from a slightly opened faucet d. smoke twisting as it moves upward from a fire ____ 14. Why does the lift on an airplane wing increase as the speed of the airplane increases? a. The pressure behind the wing becomes less than the pressure in front of the wing. b. The pressure behind the wing becomes greater than the pressure in front of the wing. c. The pressure above the wing becomes less than the pressure below the wing. d. The pressure above the wing becomes greater than the pressure below the wing. ____ 15. Which of the following occurs to a person standing near the edge of a railroad track when a high-speed train passes? a. The person tends to be pushed away from the train. b. The person tends to be pulled toward the train. c. The person tends to be pushed upward into the air. d. The person is unaffected by the train. Problem

16. The absolute pressure below the surface of a freshwater lake is 2.43  10 Pa (Absolute pressure is the sum of pressures for all layers of fluids). At what depth does this pressure occur? Assume that atmospheric pressure is 1.01  10 Pa and that the density of the water is 1.00  10 kg/m .

17. A hydraulic lift consists of two pistons that connect to each other by an incompressible fluid. If one piston has an area of 0.49 m and the other an area of 6.2 m , how large a mass can be raised by a force of 220 N exerted on the smaller piston?

18. A piece of wood with a mass of 8.71 kg is placed in fresh water ( = 1.00 g/cm ). What is the density of the wood if it has an apparent weight of –5.77 ?

. 19. An air-filled balloon with a mass of 3.0 g is placed in a pool of water. What is the buoyant force acting on the balloon if the density of air is 1.29  10–3 g/cm3 and the density of water is 1.00 g/cm3?

20. A raft with a length of 8.0 m, a width of 1.6 m, a thickness of 0.11 m, and a density of 690.0 kg/m is placed in a river. How far below the water’s surface does the bottom of the raft sink? (Recall that fresh water has a density of 1.00 10 kg/m .)

21. A fire truck pumps water into a fire hose with a diameter of 8 cm. The fireman at the other end of the hose is on a ladder. He is holding the nozzle 15 m above the pump, and the nozzle has a diameter of 5 cm. To be effective, the water must exit the nozzle at a speed of 30 m/s. What must the pressure be at the pump? (Atmospheric pressure is 1.01 x 105 Pa, and the density of water is 1000 kg / m3)