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问题 填空题

如果将时钟的时针、分针、秒针的转动看成是匀速圆周运动，则时针、分针、秒针的角速度之比为______：______：______．

答案

由公式ω=

2π
T
可知，时针的周期是12h，分针的周期是1h，它们的周期比为12：1，则角速度之比为1：12．而分针的周期60min，秒针的周期是1min，它们的周期比为60：1，所以角速度之比为1：60．因此时针、分针、秒针的角速度之比为1：12：720

故答案为：1：12：720

单项选择题

Losing a job or not being able to find one almost always brings unwelcome changes. If you’ve lost a job, the first feeling is often one of shock. On top of the loss of income, many people find the whole routine of their life is shattered, their contact with other people reduced, their ambitions halted and their identity as a worker removed.
There may be good feelings too—it’s nice to be able to lie in bed in the morning, to spend more time with children, or to have more time to think—a better job may be just around the corner. But, unless a better job does turn up, chances are the days start getting longer and the time becomes harder to fill. Many people pass through periods of difficulty in sleeping and eating. They feel irritable and depressed, often isolated and lonely.
Despite all these problems, unemployment can be a chance for a fresh start. You can discover that it provides an opportunity to sort out or rethink what you want from life and how best you can get it. You can use the time to plan how to find a new job, learn a new skill, develop your hobbies, see if you can run your own business, do some voluntary work in your community or meet new people. It’s up to you.

Unemployment provides a chance for you to rethink ______.

A．what you find and how to keep it

B．what you want and how to get it

C．how best you can do the new job

D．how best you can sort out a new job
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单项选择题

在面板混凝土浇筑施工中应控制入槽混凝土的坍落度在3～6cm，振捣器应在滑模前( )处进行振捣。

A．10cm

B．20cm

C．50cm

D．60cm
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