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问题 问答题

07年-08年我国发生了几件重大事件．①07年10月24日18时5分，我国在西昌卫星发射中心用长征三号甲运载火箭将嫦娥一号卫星成功送入太空．嫦娥一号是我国自主研制的第一颗月球探测卫星，它的发射成功，标志着我国实施绕月探测工程迈出重要一步．②2008年的南方雪灾给我国造成了巨大的损失，引起了社会各界的关注．请你从这两件大事里面各找出一点与我们所学物理知识有关的内容．提出问题或现象并作出解答．

例：问题或现象：嫦娥一号在绕月飞行的过程中受不受力的作用．

它受到月球对它的吸引力．

问题或现象1：______；解答1：______

问题或现象2：______；解答2：______．

答案

（1）火箭为什么选用氢做燃料？

答：氢的热值大，相同质量的氢与其他燃料相比，提供的能量最多．

（2）下雪后，向路面撒盐，这样做的原因是什么？

答：水中加入盐后，水的凝固点降低，这样路面上的水就不易结冰．

单项选择题

离心式鼓风机是利用气体通过高速旋转的叶轮产生（）的原理，使气体压力提高达到送风的目的。

A.向心力

B.平衡力

C.轴向力

D.离心力
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单项选择题

No woman can be too rich or too thin. This saying often attributed to the late Duchess(公爵夫人) of Windsor embodies much of the odd spirit of our times. Being thin is deemed as such a virtue.
The problem with such a view is that some people actually attempt to live by it. I myself have fantasies of slipping into narrow designer clothes. Consequently, I have been on a diet for the better—or worse—part of my life. Being rich wouldn’t be bad either, but that won’t happen unless an unknown relative dies suddenly in some distant land, leaving me millions of dollars.
Where did we go off the track When did eating butter become a sin, and a little bit of extra flesh unappealing, if not repellent All religions have certain days when people refrain from eating, and excessive eating is one of Christianity’s seven deadly sins. However until quite recently, most people had a problem getting enough to eat. In some religious groups, wealth was a symbol of probable salvation and high morals, and fatness a sign of wealth and well-being.
Today the opposite is true. We have shifted to thinness as our new mark of virtue. The result is that being fat—or even only somewhat overweight—is bad because it implies a lack of moral strength.
Our obsession with thinness is also fueled by health concerns. It is true that in this country we have more overweight people than ever before, and that, in many cases, being over weight correlates with an increased risk of heart and blood vessel disease. These diseases, however, may have as much to do with our way of life and our high-fat diets as with excess weight. And the associated risk of cancer in the digestive system may be more of a dietary problem--too much fat and a lack of fiber—than a weight problem.
The real concern, then, is not that we weigh too much, but that we neither exercise enough nor eat well. Exercise is necessary for p bones and both heart and lung health. A balanced diet without a lot of fat can also help the body avoid many diseases. We should surely stop paying so much attention to weight. Simply being thin is not enough. It is actually hazardous if those who get (or already are) thin think they are automatically healthy and thus free from paying attention to their overall lifestyle. Thinness can be pure vainglory.

Swept by the prevailing trend, the author______.

A. had to go on a diet for the greater part of her life
B. could still prevent herself from going off the track
C. had to seek help from rich distant relatives
D. had to wear highly fashionable clothes
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