题目

下列关于简单机械的说法中正确的是A.越省力的机械，机械效率越高B.吃饭时，筷子是个省力杠杆C.做功越快的机械，机械效率越高D.用滑轮组竖直吊起货物的机械效率与动滑轮的重力有关 答案：【答案】D【解析】A．机械效率高是指有用功占总功的比率较大，相同总功的时候有用功较多，而不是省力，与是否省力也没有必然的联系，故A错误；B．筷子在使用时动力臂小于阻力臂，所以是费力杠杆，故B错误；C．做功越快的机械，说明功率大，但机械效率不一定越高，机械效率还要看有用功占总Many people influenced various aspects of my life, based on their personal characteristics, accomplishments and values. I have been fortunate to have had numerous teachers and professors who I respect for their patience and intelligence. There are artists that have inspired me by their natural talents and original creativity. I value many political leaders, who have inspired me by their contributions to society, and their ability to change our futures. But of all the people I have known in my life, the person I admire most is my father. As the youngest girl in my family, I always considered myself to be “Daddy's little girl”. While I grew up, it always made me sad to see so many of my friends and neighbors without a father or father-like figure around. This helped me appreciate how my father always takes an interest in his children's lives. In every aspect of my life my father continuously pushes me to excel, so I could accomplish my work outstandingly among my people. Whenever I feel like giving up, or have a question or a concern, I know I can always call on him for advice. From him I have also learned that sometimes you have to put others' needs ahead of your own, but you should make sure you are not taken advantage of by others. His strength seems to be unbreakable during hard times, and he is extremely determined to accomplish anything he sets his mind on, no matter how tiny it is. I highly respect him for how he stands up for what he believes in, and will never back down. I have always admired his open mind, compassion(同情) for people, and sense of understanding. He is a very reserved(保守的) man, but to everybody's surprise, he has a great sense of humor, and always knows how to put a smile on the faces of his wife, his children and his friends. Living in his affection and instruction, I am very proud of my father. He also professes how proud he is of his children, and is still there to support us in whatever we are involved in1.Which of the following could not be used to describe the author's father?A.Considerate and humorousB.Affectionate and open-mindedC.Energetic and helpfulD.Learned and fashionable2.Which of the following can best explain the underlined word“excel”?A.Show offB.Do better than othersC.Be cleverer than othersD.Keep healthy3.According to the underlined part, the father was telling the author to _________A.try to be good to those who were worth making friends withB.try to take advantage of those who were friendly to herC.think about others and help them, but not to be made use of in a negative wayD.think about others and help them, so that she could make them serve her4.What can we infer about the author?A.She appreciated her father because he solved all the problems for herB.She considered her father humorous and was often made to laugh by himC.She was outstanding in work because her father pushed her hardD.She had compassion for the fatherless