问题 实验题

如图3-5-15所示,质量为m的物体用一轻绳悬挂在水平轻杆BC的端点上,C点由轻绳AC系住.已知AC与BC的夹角为θ,则轻绳AC上的拉力大小为_________,轻绳BC上的压力大小为_________.

          

图3-5-15 

答案

mg/sinθ mgcotθ

                            

取C点为研究对象,其受力如图所示.C点平衡,三个力的合力为可将G沿F1和 F2的反方向进行分解,则有F1=G1,F2=G2,由三角形知识得:tanθ=G/G1,sinθ=G/G2,故F1=Gcotθ,F2=G/sinθ,由于C点受到的拉力和支持力在数值上等于绳受到的拉力和杆受到的压力,故轻绳AC上的拉力大小为mg/sinθ,轻杆BC上的压力大小为mgcotθ.分解力时,根据解题需要进行分解,可使问题更简便.

完形填空

第Ⅱ卷

注意事项:

1.用黑色墨水的钢笔或签字笔将答案写在答题卡上。

2.本卷共6小题,共35分。

第三部分:写作

第一节:阅读表达(共5小题;每小题2分,满分10分)

阅读下面短文,并按照题目要求用英语回答问题。

When Dan Shaw gets up from the sofa in his home, Cuddles is never far away. When he wants to go outside, he doesn’t take Cuddles out for walk—Cuddles takes him for a walk. Cuddles is clearly no ordinary family pet. It is a two-foot-high miniature horse and serves as the guiding eyes of Shaw, who is blind.

When Shaw lost his sight, his wife suggested he apply for a guide dog. Shaw, an animal lover, said he couldn’t bear to part with a dog (which usually lives about eight to ten years) and get used to a new one, perhaps several times in his life.

Then Shaw heard of a program about the tiny guide horses. He learned that the horse possess many qualities that that make them an excellent choice for guiding people. They are clean friendly, smart and have great memories. They can be trained to remain calm in noisy and crowded places. Best of all, they live for 25-25years, which would enable Shaw to have the same guide companion for most or all of his life.

Shaw immediately applied to be and was accepted as the first person to receive a guide horse. The instant he met Cuddles, he knew he was making the right choice. Then he began his training.

Through training ,Shaw and Cuddles learned to find way on busy streets, step over curbs(便道沿儿)and find elevator buttons. Cuddles even demonstrated(显示)its ability to step in front of Shaw and block him, to prevent him from walking into a dangerous situation. The little horse also expertly led Shaw through busy shopping malls. They got along without any difficulties. Now Shaw is confident that Cuddles will change his life for the better.

56. What’s the meaning of the underlined word “miniature” in Paragraph 1?(No more than 2 words)

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57. Why didn’t Shaw want to choose a dog as his guide? (No more than 15 words)

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58. What does Paragraph 3 mainly tell us? (No more than 10 words)

_______________________________________________________________________________59. How does Shaw feel about his future life with the help of Cuddles? (No more than 10 words)

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60. In your opinion, what is the ideal relationship between man and animals? (No more than 20 words)

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选择题