题干

用如图所示的实验装置测量杠杆的机械效率.实验时,竖直向上匀速拉动弹簧测力计,使挂在较长杠杆下面的钩码缓缓上升.

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同类题4

阅读理解

    Long ago, a wolf called Howler lived in a valley where lots of fruit trees grew. He often tried to climb up the trees to eat the fruit, but couldn't reach.

    In the valley, an old man named Martin also had a few fruit trees that he looked after very well. But as he was getting older, he noticed that he didn't have the strength to pick the fruit.

    Martin had the most beautiful fruit trees in the valley, which was why Howler had his eye on them. One day he decided to steal the fruit and started jumping up and down the tree.

    Martin looked out of the window and realized that the wolf was trying to steal fruit from his beautiful trees. Howler jumped and jumped, but he couldn't reach even the lowest branches of such a big tree.

    Seeing this, Martin had a great idea: he offered Howler a ladder to climb up, but in return the wolf would have to give him half of the fruit. Howler accepted the deal and began to collect the fruit. For the whole morning, he went up and down the ladder filling his basket with the fruit.

    Howler soon realized that he could eat all the fruit if he didn't give Martin some. He thought up a new and secret plan. Martin, on the other hand, trusted Howler and even began to think they would be friends forever.

But the wolf stole the ladder and went off to other trees in the area for more fruit.

    Realizing that the ladder was missing, Martin went looking for it. Martin felt very disappointed at the trick and no longer trusted Howler. Though he wasn't angry with the wolf and they became friends again, he never made any more deals with him.

    At last, Howler learned that he shouldn't trick people and he should keep promises. He also learned that if he had been honest and not greedy, he would still have been able to enjoy more delicious fruit.

同类题5

名著阅读。
     ①保尔来到大海边。
     ②在遥远的地平线上,航行的轮船冒出一片片黑烟,像黑云似的散步在大海的上空。一群群海鸥尖叫着在大海上飞翔。
     ③现在,他身体彻底垮了,失去了重新归队的希望,他该怎样对待自己呢?他终于使巴扎诺娃吐露了真情。这个女医生告诉他,前面还有更可怕的事情等着他。怎么办?这个恼人的问题就摆在面前,逼着他解决。
     ④他已经失去了最宝贵的东西——战斗的能力。活着还有什么用呢?在今天,在凄凉的明天,他用什么来证明自己生活得有价值呢?又有什么来充实自己的生活呢?光是吃、喝、呼吸吗?当一名力不从心的旁观者,看着战友们向前冲杀吗?
     ⑤就这样成为队伍的累赘吗?他想起了基辅无产阶级的领袖叶夫格妮亚·博什。这位久经考验的女地下工作者得了肺结核,丧失了工作能力,不久前自杀身亡。她在简短的留言中解释了这样做的理由:“我不能接受生活的施舍。既然自己成了党的病患,我认为继续活下去是不必要的。”把背叛了自己的肉体也消灭掉,怎么样?朝心口开一枪,就完事了!过去既然能够生活得不坏,现在也应该能够适时地结束生命。一个战士不愿再受临终前痛苦的折磨,谁能去责备他呢?
      ⑥他的手摸到了口袋里光滑的勃朗宁手枪,手指习惯地抓住了枪柄。他慢慢掏出手枪。
      ⑦“谁想到你会有今天?”
      ⑧枪口轻蔑地直视着他的眼睛。他把手枪放到膝上,恶狠狠地骂了起来:“你算什么英雄,纯粹是冒牌货,老弟!任何一个笨蛋,随便什么时候,都会对自己开一枪。这样摆脱困境,是最怯懦、最省事的办法。生活不下去就一死了之,对懦夫来说,也不需要更好的出路。你试过去战胜这种生活吗?你尽一切努力冲破这铁环了吗?你忘了在诺沃格勒—沃伦斯基附近,是怎样一天发起十七次冲锋,终于排除万难,攻克了那座城市吗?把枪藏起来吧,永远也不要对任何人提起这件事。就是到了生活已经无法忍受的时候,也要善于生活下去,要竭尽全力,使生命变得有益于人民。