题干

关于重力的说法正确的是:(   )

A:若一个物体的质量分布发生变化,其重心位置可能会发生变化

B:重力的方向一定垂直于接触面

C:一质量分布均匀的砖块,平放、侧放和立放时,其重心在砖内的位置一定变化

D:只有静止的物体才会受到重力作用

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答案(点此获取答案解析)

A

同类题3

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    我离教室越来越近。传达室的挂钟告诉我,我竟迟到了30分钟!每走近一步,我的心就跳得格外剧烈。“谁叫你起得这么晚呢?你看还有十分钟,第一节课就要下了!”我暗暗责备自己,并且担心老师严厉地批评我,同学们又会投来责备的眼光……

    走到教室门口,我更慌张了。是进,还是退?我犹豫不决。但是,我忽然想到,在这关键时刻,后退一步,就是容忍自己的错误,就是向自己的弱点退让;前进一步,就是克服缺点的开始,就能多听一分钟的文化知识。想到这里,我毅然地抬脚跨进教室。

    教室里,同学们正在_______地听老师讲课。“报告!”我才喊出口,几十双眼睛“刷”地一下盯在我身上,我赶快低下头,只感到脸上阵阵发烫。这时__老师走过来__严肃又亲切地询问我__李文同学__你今天怎么来得这么迟__我_______地回答:“我……我……昨晚看电视看得太晚了,今天早上睡过了头。”我的头更低了。老师看出了我的心思,亲切地看着我坐下,诚恳地说:“珍惜这短短的几分钟吧!”我偷偷地看了一下周围,同学们的目光是和善的……

    亲切的教诲,善意的目光,使我忐忑不安的心渐渐平静下来。我暗下决心,要把损失的时间补回来。我坐好后,迅速拿出书和笔记本,用自己的纸和笔,带着悔恨和决心,认真地记下了这宝贵的几分钟学到的知识。

同类题4

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    I don't think there is anything more important than health. “Health is the greatest wealth,” wise people say. You can't be good at your studies or work well when you are ill.

    If you have a headache, toothache, backache, earache or bad pain in the stomach, if you complain of a bad cough, if you run a high temperature and have a bad cold, or if you suffer from high or low blood pressure, I think you should go to the doctor. The doctor will examine your throat, feel your pulse, test your blood pressure, take your temperature, sound your heart and lungs, test your eyes, check your teeth or have your chest X-rayed. After that, he will advise some treatment, or some medicine. The only thing you have to do is to follow his advice.

    Speaking about doctor's advice, I can't help telling you a funny story. An old gentleman came to see the doctor. The man was very ill. He told the doctor about his weakness, memory loss and serious problems with his heart and lungs. The doctor examined him and said there was no medicine for his disease. He told his patient to go to a quiet place for a month and have a good rest. He also advised him to eat a lot of meat, drink two glasses of red wine every day and take long walks. In other words, the doctor advised him to follow the rule: "Eat with pleasure, drink with pleasure and enjoy life as it is." The doctor also said that if the man wanted to be well again, he shouldn't smoke more than one cigarette a day. A month later the gentleman came into the doctor's office. He looked cheerful and happy. He thanked the doctor and said that he had never felt a healthier man." But you know, doctor," he said, “it's not easy to begin smoking at my age.”