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问题 多选题

竖直上抛的石块，最后落回抛出处，在这过程中（　　）

A．上升过程中，重力做负功，石块的动能转化为重力势能

B．上升过程中，重力做正功，石块的动能转化为重力势能

C．下降过程中，重力做负功，石块的重力势能转化为动能

D．下降过程中，重力做正功，石块的重力势能转化为动能

答案

A、上升过程中，重力向下，位移向上，重力做负功，故石块的动能转化为重力势能，故A正确，B错误；

C、下降时，重力和位移同向，故重力做正功，重力势能减小，动能增加，即重力势能转化为动能，故C，错误，D正确

故选AD

阅读理解

Years ago people could hardly accept the ideas of a woman's being a doctor.In order to get into medical school in 1847，Elizabeth Blackwell was asked to keep it a secret that she was a woman.This was contrary to her beliefs，and she refused to do it.After entering medical school，Elizabeth often had to summon(鼓起) all her courage to free the unkindness of teachers and classmates.By her great efforts，she was able to complete her studies.Many people came to her graduation just to have a look at a woman doctor.Doctor Blackwell soon found that most people were not as ready as to go to a woman doctor.She had to struggle to make a living.Then came the great day when she was offered a job as a doctor in a hospital.She did so well that she was asked to organize a new hospital and medical college.The United States can now be proud of thousands of women doctors.

小题1:How do you think Elizabeth was treated in the medical school?

A．Kindly.

B．Unfairly.　

C．Normally.　

D．Cruelly.小题2:Many people came to see Elizabeth when she graduated ______.

A．because they wanted to congratulate her on being a doctor

B．because they didn't believe she would be famous in the future

C．because they wanted to find out the secret of her success

D．because they weren't sure that she could manage to finish her schooling小题3:The underlined word “contrary” most probably means______.

A．against

B．familiar

C．wrong

D．similiar小题4:When she was at the medical school，Blackwell ______.

A．had to pretend to be a boy student in class

B．was discouraged by the others' critical looks

C．felt sorry that she was a woman

D．made great efforts to do well in her lessons
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单项选择题

冷却水冷却冷凝器中的制冷剂时，冷凝压力（）

A.增大

B.减小

C.不变
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