问题 实验题

小明想比较几种材料(衣服、锡箔纸、泡沫塑料)的隔音性能,除了待检测的材料外,可利用的器材还有:音叉、机械闹钟、鞋盒。小明将声源放入鞋盒内,在其四周塞满待测材料,以下是他设想的两种实验方案:

方案A:让人站在距鞋盒一定距离处,比较所听见声音的响度。

方案B:让人一边听声音,一边向后退,直至听不见声音为止,比较此处距鞋盒的距离。

(1)在本实验中适合作声源的是________;

(2)他设想的两种实验方案中,你认为最佳的是方案________;

(3)通过实验得到的现象如表1、2所示,则待测材料隔声性能由好到差的顺序为__________。

答案

(1)机械闹钟 (2)B  (3)泡沫塑>料衣服>锡箔纸

题目分析:在本实验中适合作声源的是机械闹钟,因为它可以持续地发出声音。让人站在距鞋盒一定距离处,比较所听见声音的响度。这样比较响度不明显。让人一边听声音,一边向后退,直至听不见声音为止,比较此处距鞋盒的距离。这样通过比较距离可以较准确地比较出材料的隔音性能。

点评:对于此题,注意要用控制变量法研究问题。

选择题
阅读理解

The search for life in the universe took a step forward last month with the opening of the Allen Telescope Array(艾伦望远镜阵列) in Hat Creek, California. The telescopes were partly made possible by a gift of twenty-five million dollars from Paul Allen. The total cost of the project is already fifty million dollars.

At present, there are 42 radio telescopes working at the Hat Creek observatory. The signals they receive are combined to create what is equal to a single, very large telescope. The telescope will be used to observe objects like exploding stars, black holes and other objects that are predicted but have not yet been observed. Seth Shostak of the SETI Institute says this is the first telescope whose main purpose is to search for signals from intelligent life in space. The SETI Institute is based in Mountain View, California. The organization supports the search for other life forms in the universe.

What makes the Allen Telescope Array unusual is that it can collect and study information from a wide area of the sky. In addition, the 42 telescopes can study information about several projects at the same time. That means studies of large areas of the sky can be made faster than ever before.

Some officials think the Allen Telescope Array will be completed in three more years. 350 individual radio telescopes are planned. The new abilities of the Allen Telescope Array will make searching for stars similar to the sun much faster.

An earlier search by SETI, Project Phoenix, studied about 800 stars to a distance of 240 light years. The project ended in 2004. With the Allen Telescope Array, astronomers hope to gather thousands of times more information in the search for life beyond our planet.

小题1:The main purpose of the Allen Telescope Array is          .

A.to serve for the research of weather predication

B.to prepare for the wars against life from the universe

C.to search for signals from intelligent life in space

D.to observe exploding stars, black holes and other objects小题2:From this passage we know that         .

A.the 42 radio telescopes at Hat Creek observatory can work together

B.the total cost of the project came from Paul Allen

C.Hat Creek observatory can receive signals from all parts of the worm

D.Hat Creek observatory is operated by an American named Paul Allen小题3:Which of the following is TRUE according to this passage?

A.The Allen Telescope Array takes much more room than former telescopes.

B.The Allen Telescope Array is still being built at present in the United States.

C.Another 42 radio telescopes will be fixed in the Allen Telescope Array.

D.The SETI Institute is against the search for other life forms in the universes.小题4:With the help of the Allen Telescope Array,         .

A.astronomers can gather more information than before from other planets

B.humans will have more chances to live on other planets than before

C.humans will be able to find more natural resources on other planets

D.scientists will be able to find more natural resources from other planets