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【判断题】

超音速气流的流速一定大于亚音速气流的流速。

A.
正确
B.
错误
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参考答案:
参考解析:
.
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举一反三

【单选题】超音速喷管是一个( )的管道。

A.
先扩张后收敛形
B.
扩张形
C.
收敛形
D.
先收敛后扩张形

【单选题】第二篇 Flying the Hypert Skies A little airplane has given new meaning to the term "going hyper. " The Hyper-X recently broke the record for air-breathing jet planes when it traveled at a h...

A.
It indicated the birth of a very fast airplane.
B.
It was self-powered, so it lasted only 11 seconds.
C.
It can transportcargo quickly and cheaply to the brink of space.
D.
It is a major milestone in the journey of making a new type of very fast airplanes.

【单选题】变速器传动比大于1,其输出转速(),转矩()。

A.
增加,降低
B.
降低,增加
C.
先增加,后降低
D.
不变