问题 问答题

如图所示,一小木块从斜面上滑下,在粗糙的水平面上滑动一段距离后便停下来.请你画出木块在水平面上滑动时的受力示意图.

答案

重心在物体的中心,过重心沿竖直向上、竖直向下以及水平向左的方向分别表示出支持力F、重力G和摩擦力f; 如图所示.

阅读理解

阅读理解。

     In 1997, a group of twenty British women made history. Working

in five teams with four women in each team,they walked to the

North Pole. Apart from one experienced female guide, the other

women were all ordinary people who had never done anything like

this in their lives before. They managed to survive in an environment

and defeated several very experienced men during the same

period.

    Once on the ice, each woman had to ski along while dragging a

sledge (雪橇) weighing over 50 kilos. The Arctic ice was pushed up

into huge piles two or three meters high, and the sledges had to be

pulled up one side and carefully let down the other all on the rough

surface so that they didn't become damaged. The temperature was

always below the freezing point and sometimes strong winds made

walking while pulling so much weight almost impossible. It was also

very difficult for them to put up their tents when they stopped each

night.

      In such conditions ,'the women were making good progress if

they covered fourteen or fifteen kilometers a day. However, part of

the journey was across a frozen sea with moving water underneath

the ice and at some points the team would drift(漂流) back more

than five kilometers during the night. That meant that after walking

in these very severe conditions for ten hours on one day, they had to

spend part of the next day covering the same ground again.

     So,how did they manage to succeed? They realized that they

were part of a team. If any one of them didn't pull her sledge or get

her job done, she would endanger the success of the whole expedition.

Any form of selfishness could result in the efforts of everyone

else being completely wasted, so personal feelings had to be put to

one side. At the end of their journey, the women agreed that it was

mental effort far more than physical fitness that got them to the

North Pole.

1. The expedition was extraordinary because________. 

A. there was no one to lead it

B. the women did not have any men with them

C. it was a new experience for most of the women

D. the women had not met one another before

2. On the expedition, the women had to be particularly careful to avoid_______. 

A. falling over on the ice

B. being left behind

C. damaging the sledges

D. getting too cold at night

3. The women could not cover 15 kilometers a day mainly because______. 

A. they got too tired

B. the ice was moving

C. they kept getting lost

D. the temperatures were too low

4. The passage seems to tell us that_________.

A. motivation and teamwork achieve goals

B. women can do anything they want

C. it is good to experience difficult conditions

D. the Arctic conditions are very severe

问答题 简答题