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A large cylindrical tank of base area 1 m² is filled with water and has a small hole 1 m above the bottom. A 5 kg frictionless piston sits on the water surface, and a 45 kg load is placed on the piston. When the piston (and water surface) is 7 m above the bottom, find the speed v of the water jet emerging from the hole. (g = 10 m/s²)
- 9 m/s
- 10 m/s
- 11 m/s
- 12 m/s
Correct answer: 11 m/s
Solution
Apply Bernoulli between the top surface (under the loaded piston) and the hole. The piston load supplies a constant gauge pressure, and the 6 m water column above the hole supplies the gravitational head.
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