1. Consider a cylindrical tank filled with water with 2.5-m depth. The water emerges from a small hole at the center of the bottom. The diameter of the hole is 1 mm. The cross-section area of the vertical water stream decreases as it falls. Find the diameter of the water stream at the position 7.5 m from the hole. (A) 0.23 mm(B) 0.36 mm(C) 0.50 mm(D) 0.58 mm(E) 0.71 mm

6. Consider a thermodynamic engine based on ideal gas. The operating cycle is shown in the pressure(P)-volume(V) diagram. The a→b and c→d are isochoric (constant volume) processes, and the b→c and d→a are adiabatic processes. Which one of the following statements is wrong? (A) During a→b, the heat flows from the engine to the surrounding.(B) During b→c, the temperature of the gas decreases.(C) During c→d, the internal energy of the gas decreases.(D) During d→a, the internal energy of the gas increases.(E) During d→a, the engine does negative work on the surrounding.

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