题目内容
有一条灌溉渠道，横截面是梯形，底宽2m,水面宽4m,水深1m。这条渠道在通过两条分渠道把水引到田间，分渠道的横截面也是梯形，底宽1m,水面宽2m,水深0.5m。如果水在两条分渠道内的流速都是2m/S,则水在总渠道中的流动速度为（）
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流体在圆柱形水平流管中稳定流动，其管心流速为（ ），填“最大”或“0”。
泊肃叶定律表明：流体的秒流量与流体的（）成反比，与（）成正比，与管道半径R的（）成正比。
Task 4 Listen to the second part of the passage and rearrange the order of the sentences below according to what you hear.[音频]1. He canceled the planned flight to Vienna and came back to wait for the owner.2. The artist found the lottery ticket in his hat.3. He was so happy that he threw the lottery ticket into the violinist's hat with 50 dollars accidentally.4. He refused to do so at the cost of losing honesty.5. George Sang bought a lottery ticket and won a prize of $500,000.6. Someone asked the young artist to take the lottery__________→__________→___________→___________→____________→____________
从3种产品中每次取2个，且同种产品可以重复取，不同的取法共有（）种.
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