一弹簧在没有挂物体时长20厘米，当挂上一个重0.49牛的钩码时，弹_爱下问搜题

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问题填空题

一弹簧在没有挂物体时长20厘米，当挂上一个重0.49牛的钩码时，弹簧伸长的长度是2厘米．若在弹簧下端再挂上2个0.49牛的钩码时，弹簧伸长的长度将是______厘米．若将所有的钩码取下，用手拉弹簧下端，使弹簧长度变为28厘米（在弹性限度内），则手的拉力为______牛．

答案

弹簧的弹性系数为：0.49N÷2cm=0.245N/cm

挂3个钩码时弹簧伸长的长度是：0.49N×3÷0.245N/cm=6cm

弹簧长度为28cm即弹簧伸长8cm时手的拉力为：8cm×0.245N/cm=1.96N

故答案是：6cm、1.96N

完形填空

Dear Mr Brown,
“Do you like my dress?" A little girl asked a passing stranger. "My mommy made it just for me." She said with tears in her eyes. "Well, I think it's very pretty. So tell me , little one, why are you 1 ?" With a quiver(颤动) in her voice the little girl answered，"After Mommy made me this dress, she had to 2 ." "Well, now," said the lady, "with a little girl like you waiting for her, I'm sure she'll be right 3 ." "No ,Madam,you don't understand," said the child through her tears," my daddy said she's up in 4 now with Grandfather. "Finally the woman 5 what the child meant, and why she was crying. Kneeling down she 6 cradled(抱着) the child in her arms and together they cried for the mommy that was gone. Then suddenly the little girl did something that the woman thought was a bit 7 .She stopped crying, stepped back from the woman and began to 8 .She sang so softly that it was almost a whisper. It was the 9 sound the woman had ever heard, almost like the song of a very small 10 . After the child stopped singing she explained to the lady, "My mommy used to sing that song to me before she went away, and she made me 11 to sing it whenever I started crying and it would make me 12 ." "See," she exclaimed, "it did, and now my eyes are13 !" As the woman turned to go, the little girl grabbed her sleeve, "Madam, can you 14 a minute? I want to show you something." "Of course," she answered, "what do you want me to see?" Pointing to a spot on her dress, she said, "Right here is where my mommy 15 my dress, and here, "pointing to another spot, "and here is another kiss, and here, and here. Mommy said that she put all those kisses on my 16 so that I would have her kisses for every booboo (错误) that made me cry." Then the lady realized that she wasn't just looking at a dress, no, she was looking at a 17 who knew that she was going away and would not be there to kiss away the 18 that she knew her daughter would get. So she took all the love she had for her beautiful little girl and put them into this dress that her child now so proudly 19 . She no longer saw a little girl in a 20 dress. She saw a child wrapped…in her mother's love.

选择题

—It's a wonderful way of getting to see Italy, and it also________cost very much.

— Terrific. [ ]

A. needn't

B. mustn't

C. couldn't

D. shouldn't