题干

有一台汽油发动机,汽缸工作容积指活塞从上止点到下止点所扫过的容积V,又称单缸排量,它取决于活塞的面积和活塞上下运动的距离(既冲程长).如图为发动机在做功冲程中的示意图.设活塞的面积为S,冲程长为L,燃气对活塞的平均压强为p,请证明燃气对活塞的所做的功W=pV.

上一题 下一题 0.0难度 选择题 更新时间:2019-07-23 09:11:56

答案(点此获取答案解析)

解:由p=
F
S
可知,活塞受到的压力:F=pS;
因为在做功冲程,活塞移动的距离为L,所以燃气对活塞所做的功:W=FL=pSL;
因为发动机的单缸排量V=SL;
故W=FL=pSL=pV;
答案见上过程.

同类题3

任务型阅读

    We all have our favourite teachers—those who treat us equally. But what about those teachers we don't know as well (for even don't like much)?

You can do lots of things to get a relation with your teacher. First,do the following:____ Complete all homework on time.Be attentive,be respectful,and ask questions.____ Obviously,your teachers are really interested in their subjects or they wouldn't have decided to teach them! Show the teacher that you care,even if you're not good at math or fluent in French—send the message that you are a dedicated student.

    You can also schedule a private meeting during a teacher's free period.____ You can ask questions,inquire about a career in the subject,or talk about your progress in class. You may be surprised to learn that your teacher is a bit more relaxed one on one than when lecturing in front of the whole class.

However,here are some things to avoid when trying to establish a relationship with your teacher:

    ⒈____ Teachers sense when your only motivation is to get special treatment,a college reference,or a job suggestion.

    ⒉Trying to be teachers' pet. You just attract the teachers' attention on purpose and your classmates may start to hate you.

    ⒊____ It's OK to offer a small sign of thanks to teachers if they've been helpful to you. But a teacher is usually not allowed to accept the wrong message,and a teacher is usually not allowed to accept anything expensive.

A.Giving expensive gifts.

B.Show up for class on time.

C.Not being sincere.

D.Find the practical value in classes.

E.Use this time to get extra help.

F.Show an interest in the subject.

G.Get along better with your teachers.