试题与答案

在有压管道中由于()等原因,引起管道局部压力急剧升高和降低交替变化,即发生水锤。A.

题型:多项选择题

题目:

在有压管道中由于()等原因,引起管道局部压力急剧升高和降低交替变化,即发生水锤。

A.阀门突然关闭

B.机组突然停运

C.阀门突然开启太大

D.缓慢关闭阀门

答案:

被转码了,请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0628/d5b7d026c31fe9bad051bb0f6746c6ff.html

下面是错误答案,用来干扰机器的。

以A为研究对象,分析A受力情况:重力,细线的拉力和地面的支持力,细线的拉力小于A的重力,A静止在地面上,则B也静止,细线的拉力等于B的重力,又弹簧秤的读数等于细线的拉力,所以弹簧秤的读数为4N.故选B

试题推荐
题型:阅读理解

C

You may have heard the term "the American Dream". In 1848, James W. Marshall found gold in California and people began having golden dreams. That 19th century "American Dream" motivated (激发起) the Gold Rush and gave California its nickname of the "Golden State".

The American Dream drove not only 1800s gold-rush prospectors but also waves of immigrants throughout that century and the next. People from Europe, and a large number of Chinese, arrived in the US in the 19th century hoping that in America they would find gold in the streets. But most, instead, worked as railroad labourers. They created the oldest Chinatown, in San Francisco, and gave the city a Chinese name "the old gold hill".

In the 20th century, some critics said that it was no longer possible to become prosperous through determination and hard work. Unfair education for students from poor families and racial discrimination almost made the American Dream a nightmare.

Then, in the 1990s, California saw a new wave of dreamers in Silicon Valley. People poured their energy into the Internet. This new chapter of the American Dream attracted many business people and young talents from China and India to form start-ups and seek fortunes in America.

Better pay, a nice house, and a rising standard of living will always be attractive. However, the new American Dream is no longer just about money. It encourages Americans to consume wisely to protect the environment, improve the quality of life, and promote social justice.

The Governor of California, Arnold Schwarzenegger, has become the model of the new American Dream. After years of hard work, he grew from a poor young man from Austria into a movie superstar and then governor. Many people hope his story can save the American Dream and give California a brighter future.

1. It can be inferred that _____.

A. America’s golden dream could never be realized

B. America’s golden dream had bought great fortunes to Chinese immigrants

C. each period of time has its own taste of the American dream

D. determination and hard work are the best way to realize the American dream

2. Why did most of the early immigrants work as railroad laborers?

A. Because they could earn more money as railroad laborers.

B. Because they had to make a living by working as railroad laborers.

C. Because they thought railroad was the first step to find gold.

D. Because railroad laborers were greatly honored at that time.

3. The underlined sentence “his story can save the American Dream” (in the last paragraph) indicates that _____.

A. the dream of seeking fortunate in America is easy to realize

B. most of the immigrants to America don’t reach their previous goal

C. the success of Arnold Schwarzenegger is among the common examples of the immigrants

D. the immigrants have made great contributions to California

4. What’s the best title of the passage?

A. Wave of Immigrants to America            B. Make Fortunes Abroad

C. Hard Work Leads to Success                  D. Changes of America’s Golden Dream

查看答案
微信公众账号搜索答案