问题
问答题 简答题
有人说“均匀流一定是恒定流”，这种说法是否正确？为什么？
答案
参考答案：
这种说法是错误的，均匀流不一定是恒定流。因均匀流是相对于空间而言，即运动要素沿流程不变，而恒定流是相对于时间而言，即运动要素不随时间而变。两者判别标准不同。
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有人说“均匀流一定是恒定流”，这种说法是否正确？为什么？
参考答案：
这种说法是错误的，均匀流不一定是恒定流。因均匀流是相对于空间而言，即运动要素沿流程不变，而恒定流是相对于时间而言，即运动要素不随时间而变。两者判别标准不同。
Stop! Listen! What do you hear? You may hear many different sounds. Some of those sounds may be noisy. Noise is loud and unwanted sound. Noise can be caused by many kinds of machines, such as motorcycles, jet planes, tractors and so on. And, to some people, rock bands are also noise. What happened to people who live near noisy machines or use them over a period of time? Doctors find that these people have trouble in sleeping, But, most important, constant loud noise can cause a loss of hearing. Scientists use a unit of measure called a decibel to measure the loudness of a sound. The sound of a quiet room, for example, measures 35 decibels. Talking measures between 40 and 65 decibels. Sounds from traffic and from some rock bands can measure over 120 decibels. Noise at this high level causes the greatest hearing loss. 小题1: From the article we know noise is ___________. wanted sound B. loud and unwanted sound C. all sounds that you can hear D. comfortable sound 小题2: A “decibel” is a _________
help people sleep better B. stop machine C. cause a loss of hearing D. kill people 小题4:The main idea of this passage is that __________ noise pollution can be a serious problem rock bands are noisy noise can cause people to be mad some people hate noise deeply 小题5: Study the chart below, Which room would be the quietest?
C. Room C D. Room D |