Homework 10 Problems – Properties of Fluids 1. [10 points] The gravitational force exerted on a solid object is 5.00 N as measured when the object is suspended from a spring scale as shown below. When the suspended object is submerged in water, the scale reads 3.50 N. Find the density of the object. 2. [10 points] A boat carrying a large boulder is floating on a lake. The boulder is thrown overboard and sinks. How should the water level in the lake (with respect to the shore) change? Defend your answer using Archimedes’ principle. 3. [10 points] (a) Tornadoes and hurricanes often lift the roofs of houses. Explain why. Why should you keep your windows open under these conditions? (b) Many people believe that a vacuum created inside a vacuum cleaner causes particles of dirt to be drawn in. Actually, the dirt is pushed in. Explain. 4. [10 points] A liquid (ρ=1.65 g/cm3) flows through a horizontal pipe of varying cross section as seen below. In the section, the cross-sectional area is 10.0 cm2, the flow speed is 275 cm/s, and the pressure is 1.20 x 105 Pa. In the second section, the cross-sectional area is 2.50 cm2. Calculate the smaller section’s flow speed and pressure. (5 points) 5. [10 points] Water moves through a constricted pipe in steady, ideal flow. At the lower point shown below, the pressure is 1.75 x 105 Pa and the pipe radius is 3.00 cm. At the higher point located at y = 2.50 m, the pressure is 1.20 x 105 Pa and the pipe radius is 1.50 cm. a. Find the speed of the flow in the lower section b. Find the speed of the flow in the upper section c. Find the volume flow rate through the pipe Bonus: [5 points] A jet of water squirts out horizontally from a hole near the bottom of the tank, shown below. If the hole has a diameter of 3.50 mm, what is the height h of the water level in the tank?
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