电气化铁路的输电线常用图所示的方式悬挂在钢缆上.钢缆的A端固定在电杆上,B端连接

题型:选择题

问题:

电气化铁路的输电线常用图所示的方式悬挂在钢缆上.钢缆的A端固定在电杆上,B端连接在滑轮组上.滑轮组由a、b、c三个滑轮构成,配重P由多个混凝土圆盘悬挂在一起组成,配重的总重为G,若不计摩擦和滑轮的重量,则以下说法中正确的是(  )

A.a为动滑轮,B端钢缆受到滑轮组的拉力大小约为3G

B.a为动滑轮,B端钢缆受到滑轮组的拉力大小约为G

C.a、c为动滑轮,B端钢缆受到滑轮组的拉力大小约为3G

D.a、c为动滑轮,B端钢缆受到滑轮组的拉力大小约为G

考点:定滑轮及其工作特点动滑轮及其工作特点
题型:选择题

We all know the dangers of fires. It’s good and necessary for a family to learn how to prepare for a fire. Here are some suggestions.

Put a smoke alarm in the house. Smoke from a fire causes the alarm to go off. The alarm makes a loud sound. The sound tells everyone to leave the house at once.

Make escape plans. We should know all the ways out of the house. If there is a fire, everyone follows the plan to get out. Part of the plan is to check all the windows to make sure they can be opened easily.

Buy fire extinguishers(灭火器) in the house. Everyone in the family should know how to use them.

Practise for a fire. We do fire practice because we teach children about fire safety. Everyone in the family should know the following fire rules:

★Don’t open a hot door! The fire can grow more quickly if you open the door.

★Stay close to the floor! Smoke can be more dangerous than fire. The best air is near the floor because smoke rises.

★What will you do if your hair or clothes start to burn? First, stop! Don’t run! The fire burns faster because of more air. Drop! Fall to the floor. Then roll! Turning over and over will make the fire go out. Put a blanket(毯子) around you to keep air away from the fire that may still be on you.

There are many possible causes for fires. A wise family is ready all the time. If there is a fire, don’t forget to call 119 for help.

根据短文内容,选择正确答案。

小题1: When a smoke alarm rings at home, it means _________.

A.you have to get up

B.water is running to the floor

C.something is burning

D.someone breaks your window小题2: The writer advises us to do the following to prepare for a fire, which one is not right?

A.we practise for a fire

B.we make escape plans

C.we buy fire extinguishers

D.we use electrical cookers小题3: When a fire happens,____ if you open the hot door.

A.the door will soon be on fire

B.the electricity will be cut off

C.the fire will grow more quickly

D.the house will fall down小题4:What are the right steps you should take when your hair or clothes catch fire?

A.Stop, run, roll.

B.Stop, drop, roll.

C.Run, drop, roll.

D.Roll, drop, stop.小题5: What is the best title for this passage?

A.Be Ready for a Fire.

B.The Causes of a Fire.

C.Learn to Use a Fire Extinguisher.

D.The Dangers of a Fire.

题型:选择题

MR图像上金属伪影一般出现在()。

A.金属植入物上方

B.金属植入物对侧

C.金属植入物周围

D.金属植入物内部

E.整个MRI图像上满布伪影

题型:选择题

重症肌无力的发病机制可能是().

A.突触后膜乙酞胆碱受体敏感性降低和受体数目减少

B.突触前膜乙酞胆碱释放减少

C.乙酞胆碱酯酶活性降低

D.乙酞胆碱酯酶活性增高

E.以上均不是

题型:选择题

先天性甲状腺功能减退最主要的原因是甲状腺不发育或发育不全。

题型:选择题

录用人民警察的程序中第1条就是要发布报考公告,报考公告应在考试前一定时间,通过公安机关内部通知的形式,让报考者有所准备。( )

更多题库