问题 选择题

关于声现象的说法,正确的是(       )

A.雷雨天气,先看到远处的闪电,稍后听到雷声

B.击鼓的力量越大,音调越高

C.声波具有传递能量的性质

D.声音只能在空气中传播

答案

AC

A闪电和雷声是同时发生的,根据传播速度表可知,声音的传播速度是340米/秒,光的传播速度是3×108米/秒,那么我们先看到闪电,后听到雷声的原因是空气中光的传播速度大于声音的传播速度,此选项正确;B运动员越用力击鼓,鼓面振动的幅度越大,鼓声的响度就越大,此选项错误;

C声音可以传递信息,如:隆隆的雷声预示着一场可能的大雨,“声呐”的利用、医用“B超”等;声音能够传递能量,如:利用声波来清洗钟表等精细的机械,“超声波碎石”等,此选项正确;D声音的传播是需要介质的,它既可以在气体中传播,也可以在固体和液体中传播,但不能在真空中传播,此选项错误。

单项选择题
阅读理解

Expressions about water are almost as common as water itself. But many of the expressions using water have unpleasant meanings.

The expression “to be in hot water" is one of them. It is a very old expression. “Hot water” was used 500 years ago to mean being in trouble. One story says it got that meaning from the custom of throwing extremely hot water down on enemies attacking a castle.

That no longer happens. But we still get in “hot water”.When we are in “hot water”, we are in trouble. It can be any kind of trouble—serious or not so serious. A person who breaks a law can be in hot water with the police. A young boy can be in hot water with his mother. if he walks in the house with dirty shoes.

Being in “deep water” is almost the same as being in hot water. When you are in deep water, you are in a difficult position. Imagine a person who cannot swim being thrown in water over his head.

You are in deep water when you are facing a problem that you do not have the ability to solve. The problem is too deep. You can be in deep water, for example, if you invest in stocks without knowing anything about the stock market.

“To keep your head above water” is a colorful expression that means staying out of debt. A company seeks to keep its head above water during economic hard times. A man who loses his job tries to keep his head above water until he finds a new job.

“Water over the dam” is another expression about a past event. It is something that is finished. It cannot be changed. The expression comes from the idea that water that has flowed over a dam cannot be brought back again.

小题1:Which of the following two expressions have almost the same meaning?

A.To be in hot water;To be in deep water.

B.To be in hot water;To keep your head above water.

C.To be in deep water;Water over the dam.

D.Water over the dam;To be in hot water.小题2:If a person tries to keep his head out of water,we can say that       .

A.he is in danger of losing his life

B.he is trying to pay off his debt

C.he is trying to keep his promise

D.he is trying not to get into debt小题3:What can you infer from the passage?

A.“To be in hot water” can only be used to mention serious trouble.

B.“Water over the dam” is an expression about a future event.

C.Water could be used in the war in the past.

D.All of the expressions using water have unpleasant meanings.小题4:This passage is written mainly to tell us        .

A.the use of water

B.how to use some expressions about water

C.expressions about water and their meanings

D.expressions with negative meaning