问题 选择题

有一种杂技表演叫“飞车走壁”,由杂技演员驾驶摩托车沿圆台形表演台的侧壁,做匀速圆周运动.右图中粗线圆表示摩托车的行驶轨迹,轨迹离地面的高度为h,下列说法中正确的是(  )

A.h越高,摩托车对侧壁的压力将越大

B.h越高,摩托车做圆周运动的向心力将越大

C.h越高,摩托车做圆周运动的周期将越小

D.h越高,摩托车做圆周运动的线速度将越大

答案

A、摩托车做匀速圆周运动,提供圆周运动的向心力是重力mg和支持力F的合力,作出力图.设圆台侧壁与竖直方向的夹角为α,侧壁对摩托车的支持力F=

mg
sinα
不变,则摩托车对侧壁的压力不变.故A错误.

    B、如图向心力Fn=mgcotα,m,α不变,向心力大小不变.故B错误.

    C、根据牛顿第二定律得Fn=m

4π2
T2
r,h越高,r越大,Fn不变,则T越大.故C错误.

    D、根据牛顿第二定律得Fn=m

v2
r
,h越高,r越大,Fn不变,则v越大.故D正确.

故选D

单项选择题
阅读理解

阅读理解。

     If you know exactly what you want, the best way to get a job is to get specialized training. A recent

report shows that companies like graduates in such fields as business and health care who can go to work

immediately with very little on-the-job training.

     That's especially true of booming fields that are challenging for workers. At Cornell's School of Hotel

Administration, for example, bachelor's degree graduates get an average of four or five job offers with salaries

ranging from the high to low and plenty of chances for rapid advancement. Large companies especially like

a background of formal education coupled with work experience. But in the long run, too much specialization

does not pay off. Business, which has been flooded with MBAs, no longer considers the degree an automatic

stamp of approval. The MBA may open doors and command a higher salary initially, but the impact of a degree

washes out after five years.

     As further evidence of the erosion of corporate faith in specialized degrees, Michigan State's Scheetz cites

a pattern in corporate hiring practices. Although companies tend to take on specialists as new hires, they often

seek out generalists for middle and upper-level management. This sounds like a formal statement that you

approve of the liberal-arts (文科) graduate. Time and again labor-market analysts mention a need for talents

that liberal-arts majors are assumed to have: writing and communication skills, organizational skills, open-

mindedness and adaptability, and the ability to analyze and solve problems. David Birch, manager of the Boston

Red Sox, says that he does not hire anybody with an MBA or an engineering degree."I hire only liberal-arts

people because they have a less-than-canned way of doing things," says Birch.

     For a liberal-arts degree, students focus on some basic courses that include literature history, mathematics,

economics, science, human behavior and a computer course or two. With these useful and important courses,

you can feel free to specialize, "A liberal-arts degree coupled with an MBA or some other technical training is

a very good combination in the marketplace," says Scheetz.

1. The job market is in great need of people with _____. [ ]

A. special training in special fields

B. a bachelor's degree in education

C. formal schooling and work experience

D. an MBA degree from top universities

2. The underlined sentence in Paragraph 2 means _____. [ ]

A. an MBA degree does not help in future promotion

B. MBA programs will not be as popular as they are now

C. people will not forget the degree the MBA graduates have got

D. most MBA programs fail to provide students with a foundation

3. David Birch says that he only hires liberal - arts people because _____. [ ]

A. they will follow others' ways of solving problems

B. they can do better in bundling changing situations

C. they are well trained in a variety of specialized fields

D. they have attended special programs in management

4. The author supports the idea that _____. [ ]

A. on-the-job training is less costly in the long run

B. formal schooling is less important than job training

C. specialists are more expensive to hire than generalists

D. generalists will do better than specialists in management