问题 计算题

已知地球半径为R,地球表面重力加速度为g,不考虑地球自转的影响。

⑴推导第一宇宙速度的表达式;

⑵若卫星绕地球做匀速圆周运动,运行轨道距离地面高度为h,求卫星的运行周期T。

答案

解:⑴设卫星的质量为m,地球的质量为M,在地球表面附近满足:

(2分)

解得:①(2分)

卫星做圆周运动的向心力等于它受到的万有引力:②(3分)

①式代入②式,得到:(2分)

⑵考虑①式,卫星受到的万有引力为:③(3分)

由牛顿第二定律有:④(2分)

③④联立解得:(2分)

完形填空

阅读表达(共5小题;每小题3分,共15分)

阅读下面的短文,并根据要求回答后面的问题。(注意字数要求)

[1] If you are applying for an American higher education, you probably dream of getting into an Ivy League (常青藤联盟) university.The eight schools with the best reputations attract top students from the United States and many other countries.However, on average, the Ivy League schools accept less than 15 percent of applicants.And with the applicants growing in size year on year, it is becoming more and more difficult _________.

[2] So how can you give yourself the best chance of admission?

[3]Having a high school grade point average (GPA) in the top 10 percent of your class and being ranked among the top few students dramatically betters your chances.But although GPA and SAT scores are important, they only tell admission deans(主任) part of the story.

[4] The whole admissions process will single out (挑选出) from a large pool of academically strong applicants the unique individuals.They stand out because they have shown in their interviews a range of virtues (优点) expected of these universities.Take Harvard for example.Although there is no guarantee of admission, the school judges applicants based on 15 additional criteria.

[5] Intellectual curiosity (求知欲) comes first tor almost all admission deans.Schools look to such students because they believe their peers find them slimulaling(激励人的)inside and outside the classroom.

[6] Leadership also weighs heavily.The school would rather see an applicant who takes on additional responsibility in one or two areas where he or she is good at, rather than one who is merely "very good" academically.This can mean the class presidencv( * * 职务), leading the cheerleading team or being the officer of a student union.

[7] Whether a person has personal warmth and cares about others counts a lot with the admission deans.Writing an essay on a personal experience, like a summer spent raising funds for the earthquake victims or teaching in a local school, can show that a person has qualities in addition to academic experience.

76.What is the purpose of the passage? (no more than 15 words)

77.Which sentence in the passage can be replaced by the following one?

The universities pay attention to the students with this virtue in that they can inspire their fellow students at school.

78.Fill in the blank in the first paragraph with proper words or phrases to complete the sentence. (no more than 5 words)

79.Based on the passage, list three additional criteria for admission besides academic performance.(no more than 10 words)

①_________________ ②_______________ ③____________________

80.Translate the underlined sentence in the fourth paragraph into Chinese.

单项选择题