如图是自行车传动机构的示意图,其中Ⅰ是大齿轮,Ⅱ是小齿轮,Ⅲ是后轮. (1)假设

题型:问答题

问题:

如图是自行车传动机构的示意图,其中Ⅰ是大齿轮,Ⅱ是小齿轮,Ⅲ是后轮.

(1)假设脚踏板的转速为 n r/s,则大齿轮的角速度是______rad/s.

(2)要知道在这种情况下自行车前进的速度有多大,除需要测量大齿轮Ⅰ的半径r1,小齿轮Ⅱ的半径 r2外,还需要测量的物理量是______.

(3)用上述量推导出自行车前进速度的表达式:______.

考点:线速度角速度
题型:问答题
已知sin(α+β)=
5
13
tanβ=
1
2
,且α,β∈(0,π).
(Ⅰ)求sinβ,cosβ的值;
(Ⅱ)求sinα.
题型:问答题

在每日摄入的总能量中,早、中、晚餐的能量应当分别占________、________、_______。

题型:问答题

What do those countries have in common? People are killing each other or drive others out of their homes. Why is this happening? Very simple, in each of these, one group of people believes another group is different from them and dangerous to them. It has been thus through history. How different are humans from each other?

We come in different colors: red, black, white, yellow and brown; we have a variety of political systems, social systems, religious views or none at all; We are different in mind, have different educational systems, different economic classes. We speak different languages, and have different customs and dresses.

If we were to break each of these further, we would have quite a long list of qualities and characteristics that make humans appears to be different from each other. I say they appear to be different, because most of what have been listed stand for what we see or hear, not what is true of human. Man is man everywhere. It is only where he lives, when he lives there, with whom he lives there, and al the others that have effect on how he lives, that is, what he believes, what he wears, his customs, his language and so on. These are man-made facts that each group develops over tome, living together, facing the same problems, needing and desiring the same things. They are his culture. The truth is that we are much more same than different. If you wear one type of clothing and I wear another, we both wear some kind of clothing. Our culture demands it. If you speak one language and I another, we both speak so that others will understand us; we must communicate with each other. Nothing is gained by giving too many differences, but much is lost. If we understood our differences as the ones of culture, then we could make our world more peaceful.

Differences does not mean better or worse, right or wrong. It means only that differences have been made by society. Differences produce variety of thoughts, work out human problems peacefully.

小题1: Which of the following is the best tile for this passage?

A.Differences.

B.Humans

C.Cultures.

D.Customs.小题2:People in those countries fight each other because______

A.They have different colors.

B.They have different customs and dresses.

C.They have different education systems.

D.They think that others are different and harmful.小题3:If you pay much attention to differences, ________.

A.we will get something.

B.we will produce problem.

C.we will develop further.

D.Nothing will be lost.小题4: From this passage it can be inferred that ________.

A.Our world would be more peaceful if we understand and communicate with each other.

B.People don’t know how differences are caused.

C.It is only differences that can solve man’s problems.

D.Man is man everywhere but not woman.

题型:问答题

“一事一议”资金是()。

A.上级拨入的资金

B.负债的资金

C.可供分配收入的资金

D.为专项事务从村民中筹集的专项资金

题型:问答题

端接接头仅在厚板焊接时采用。

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