题干

小金用橡皮筋自制测力计,选用的器材有:50g的钩码10个、挂钩、可悬挂的盒盖、硬纸板、笔、钉子(挂橡皮筋用).橡皮筋的伸长和拉力看作成正比.他想要测量铅笔盒的重力(质量大于100g),下列评价或改进错误的是(  )

A:实验还需要的器材是刻度尺

B:自制时选择不同位置的指针起点(如:橡皮筋最下端,挂钩最下端),不影响测量结果

C:自制时分别将1个和2个钩码放在盒盖中,在硬纸板上标上2个刻度.后用铅笔盒替换钩码,测得它的重力

D:若量程太小,可加一根相同的橡皮筋并联使用,改变刻度

上一题 下一题 0.0难度 选择题 更新时间:2013-01-29 09:42:57

答案(点此获取答案解析)

C

同类题4

阅读理解

    Two thieves came to a house to steal something, they dug a hole in the wall of the house.

    There lived many mice in the house. The woman in the moonlight saw a mouse crawl (爬行) into the house. “Look! In comes one,” she said to the man in the house. He was so frightened that he hurriedly crawled out of the house and said to the one waiting outside, “She found me when I was just in.” But the thief outside didn't believe him, so he said, “Let us two try to crawl into the house together.” At that time two mice happened to crawl into the house, too. The woman saw the mice and shouted, “In come two, catch them!” The two thieves were terribly frightened. The man in the house said, “You saw them come in but where are they? I will catch them tonight.” The two thieves started running away at once.

    The two thieves wanted to make it clear whether they had been found or not the night before. The next day they acted as men selling sweet potatoes and came before the house. The man and the woman were ploughing in their fields. The rein (缰绳) broke and the woman came home for a rope. She saw two men selling sweet potatoes and wanted to buy some. She picked out two which looked like mice. At the time the man couldn't wait for her any longer in the fields and he ran back from the fields to hurry her up. The woman showed the sweet potatoes to the man and said, “How they look like the two of last night.” The man said, “I asked you to fetch a rope, why don't you hurry for it?” The two thieves ran away very quickly without their sweet potatoes.