总质量为2500t的轮船经宜昌航行到三峡大坝处(根据“大船爬楼梯,小船坐电梯”的

题型:填空题

问题:

总质量为2500t的轮船经宜昌航行到三峡大坝处(根据“大船爬楼梯,小船坐电梯”的分流原则,3000t以上的大船才能允许通过5级船闸),由三峡升船机匀速吊越过坝.若升船机的船箱长120m、宽18m、深3.5m.轮船开进船箱后,大型起吊机将装有水和轮船的船箱全部悬吊起来,如图所示,其总质量为11800t,最大升程为113m.求此次吊越过坝中,升船机对轮船所做的功______,升船机的工作效率______.(g=10N/kg)

考点:功的计算机械效率的计算热机的效率
题型:填空题

阅读理解

     Think about the different ways that people use the wind. You can use it to fly a kite or to sail a boat.

Wind is one of our cleanest and richest power sources(来源) as well as one of the oldest. Evidence shows that windmills(风车)began to be used in ancient Iran back in the seventh century BC. They were first

introduced to Europe during the 1100s, when armies returned from the Middle East with knowledge of

using wind power.

    For many centuries, people used windmills to grind(磨碎)wheat into flour or pump water from deep

underground. When electricity was discovered in the late 1800s. people living in remote areas began to use them to produce electricity. This allowed them to have electric lights and radio. However, by the1940s

when electricity was available to people in almost all areas of the United States, windmills were rarely

used.

     During the 1970s,people started becoming concerned about the pollution that is created when coal and gas are burned to produce electricity .People also realized that the supply of coal and gas would not last

forever .Then, wind was rediscovered ,though it means higher costs. Today ,there is a global movement to supply more and more of our electricity through the use of wind.

1. From the text we know that windmills

A. were invented by European armies            

B. have a history of more than 2,800 years

C. used to supply power to radio in remote areas    

D. have rarely been used since electricity was discovered

2. What was a new use for wind power in the late 19th century?

A. Sailing a boat.                            

B. Producing electricity

C. Grinding wheat into flour.                  

D. Pumping water from underground

3. One of the reasons wind was rediscovered in the 1970s is that_________.

A. wind power is cleaner                    

B. it is one of the oldest power sources

C. it was cheaper to create energy from wind    

D. the supply of coal and gas failed to meet needs

4. What would the author probably discuss in the paragraph that follows?

A. The advantages of wind power.            

B. The design of wind power plants.

C. The worldwide movement to save energy  

D. The global trend towards producing power from wind

题型:填空题

下列选项中,属于分馏塔冲塔现象的是()。

A、分馏塔温度快速下降

B、分馏塔温度没变化

C、分馏塔温度快速上升

D、无法确定

题型:填空题

质量检测试样的取样应当严格执行有关工程建设标准和国家有关规定,在()监督下现场取样。提供质量检测试样的单位和个人,应当对试样的真实性负责。

A.建设单位或工程监理单位

B.建设单位或质量监督机构

C.施工单位或工程监理单位

D.质量监督机构或工程监理单位

题型:填空题

头脑风暴法的时间一般在多长为宜()

A.10-30分钟

B.20-60分钟

C.60-120分钟

D.1-10分钟

题型:填空题

X精子的DNA比Y精子()。

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