问题 填空题

汽油机的一个工作循环中,将机械能转化为内能的冲程是______冲程;将内能转化为机械能的冲程是______冲程;不是利用飞轮惯性完成的冲程是______冲程;如飞轮转速为3000r/min,则汽油机每秒完成______个冲程,对外做功______次.

答案

(1)汽油机的一个工作循环中,在做功冲程中,气体推动活塞对外做功,将气体的内能转化为活塞的机械能;在压缩冲程中,将机械能转化为内能;

(2)在做功冲程中,燃气推动活塞对外做功,不是利用飞轮惯性完成;

(3)汽油机的一个工作循环中,曲轴转一圈,完成2个冲程,并对外做功1次.由题意可知,单缸四冲程汽油机的飞轮转速是3000r/min,即每秒钟转50圈,所以,完成100个冲程,做功25次.

故答案为:压缩;做功;做功;100;25.

阅读理解

James is a good student and he has lots of friends,but he also has a problem.Some older boys are bullying(欺负)him at school.James is very unhappy and he doesn’t know what to do about it.Here are some suggestions to him and other teenagers in this situation.

Don’t feel worried.It’s not your fault(过错)! Being bullied can make you feel very lonely and angry,but you are not alone.Don’t feel that you have to hide the problem.You should find a person you can trust,and tell them.It might be your teacher,your parents,or even your friend’s parents.After you tell someone,you will get some support and feel some relief(解脱).

Speaking to an adult might make you nervous,but here are other things you can do.Some people express their feelings more easily on paper.Write a letter to someone or keep a diary.Include all the details(细节)about what the bullies do, as well as when and where the bullying happens.You can use it as proof to show what is going on.And it is a wonderful idea to

show your letter or diary to a teacher or another responsible adult.Then the bullies will feel very afraid if their names appear in a letter!

Also,don’t show you are sad and don’t try and fight with the bullies. You could get in trouble yourself. Ignore them and just walk away. The bullies will soon stop.

小题1:What do you think the text is trying to tell us?

A.What to do about being bullied.

B.How to be a good student at school.

C.What to write well in a diary.

D.How to give suggestions to teenagers.小题2:Why does the text advise you not to feel worried if bullied?

A.Because you are not alone.

B.Because it is not your fault.

C.Because someone has known about it.

D.Because you’ re doing something wrong.小题3:You’d better go and find a person you can trust and ____.

A.know what happens

B.learn from them

C.ask for help

D.make them lonely小题4:If you remember and follow the suggestions above, ____.

A.nobody will speak to the bullies

B.everybody will feel some relief

C.someone will express their feelings

D.the bullies will soon stop小题5:What does the underlined word "ignore" mean in the text?

A.take no notice of

B.take care of

C.make full use of

D.get more help from

单项选择题