问题
单项选择题
输油管直径d＝150mm，油的运动黏性系数v＝0.2cm2／s则保持管中流动为层流的最大流速为（）。
A.0.5m／s
B.0.307m／s
C.0.534m／s
D.1m／s
答案
参考答案：B
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输油管直径d＝150mm，油的运动黏性系数v＝0.2cm2／s则保持管中流动为层流的最大流速为（）。
A.0.5m／s
B.0.307m／s
C.0.534m／s
D.1m／s
参考答案：B
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| I agree with the saying that some people “see old memories as a chance to deal with the past and unite past and present.” Many people are so 1 by things that happened in their past that they are not able to focus on the 2 . For example, in the book Ceremony, the main character, Tayo, cannot concentrate on the present because he can’t forget his troubled childhood and 3 continues to relive things that happened during that time. However, past memories can help people to 4 in the present. A 5 example of people learning from the past would be the Marshall Plan. After the 6 of World War II there were many war-torn countries around the world in need of 7 assistance to help rebuild their countries, and the United States would have to be the one to 8 that assistance. Many American politicians thought it was 9 for the US government to spend money abroad on countries that would not be able to repay it for a long time. However, George Marshall, a former US general, remembered how the exact same 10 of "why should we spend money on war-torn nations that really owe us reparations (赔款)?" had been used after World War I towards Germany. The 11 of assistance towards Germany after World War I had caused a gigantic economic depression in Germany that had made the Mark (German money) virtually 12 . The German people became so desperate that they started 13 an extreme German nationalist named Adolf Hitler, who eventually started World War II. Marshall knew that if the US did not 14 war-torn Germany and, especially, Japan, we could 15 have a World War III on our hands. | ||||
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