家用的手摇晾衣架如图所示,它实际是由定滑轮和动滑轮组成的滑轮组。假设衣服和晾衣架

题型:选择题

问题:

家用的手摇晾衣架如图所示,它实际是由定滑轮和动滑轮组成的滑轮组。假设衣服和晾衣架的总重为100N,则静止时绳子自由端的拉力为(不计动滑轮重及摩擦)(   )

A.100N

B.50N

C.25N

D.20N

考点:杠杆及其五要素
题型:选择题

第Ⅱ卷

第一节 短文填空(共10分)

The Story of My Life by Helen Keller is

the most ____________(有影响的) book in my life.                      1. ___________

It is filled _________ courage, struggle and faith throughout.               2. ___________

Helen Keller was once in deep despair in her childhood, but finally she decided

to o________ her physical disabilities and live happily.                    3. ___________

Furthermore, she showed great patience  ______  her long and            4. ___________

hard learning period. I have learned, above all, two lessons from her story. First, she taught me that often the road to s________  is to                                 5. ____________     

face hardships ______(勇敢地). Maybe you are born under an ill           6.____________

star yet you can stand a better chance ________ others.                    7.____________            

It is therefore important that you screw up your courage when courage is needed.

Second, the damaged part of her senses did not p______ her learning.         8.____________

On the ___________, she had made                                    9. ___________

continual ________(努力) to go deeper into the field of knowledge.          10. ___________

题型:选择题

电镜主要分为()和()两类。

题型:选择题

关于日本的叙述,正确的是[ ]

A.国土面积比较小,人口稠密

B.森里覆盖率低,每年大量进口木材

C.水能资源和矿产资源丰富

D.渔业不发达

题型:选择题

婴儿及早产儿手术时要求最佳周围环境温度是()

A.24℃

B.26℃

C.27℃

D.28℃

E.29℃

题型:选择题

试举出5种鉴别面料经向的方法?

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