问题 选择题

物体(可看做质点)在力F作用下沿粗糙水平面做直线运动,关于物体的受力情况正确的是(  )(不计空气阻力)

A.一定只受两个力

B.可能只受两个力

C.可能受到四个力

D.受三个或四个力均可能

答案

BC

题目分析:当拉力F的竖直分量等于重力时,物体可沿粗糙水平面做直线运动,此水平面对时物体没有支持力,只受重力和拉力两个力作用;若果拉力F的竖直分量小于重力时,且拉力的水平分量大于等于摩擦力时,物体可沿沿粗糙水平面做直线运动,此种情况下物体受重力、支持力、拉力F和摩擦力四个力作用。

故选BC

点评:分析物体受力时要考虑会出现的各种可能情况。

阅读理解

Chelsea Clinton, the 31-year-old daughter of former President Bill Clinton and Secretary of State Hillary Rodham Clinton, is stepping into her own spotlight.

According to the New York Times, NBC has hired Clinton to become a full-time special correspondent(记者) for NBC News. Her feature stories will reportedly be used in the “Making a Difference” series, which runs on “NBC Nightly News”. The sections attract people who volunteer to improve the lives of others in their communities.

When Bill Clinton won the presidency in 1992, the first lady asked the press to keep Chelsea out of the public eyes. As a young adult, Chelsea continued to avoid media attention in order to attend college and quietly enter the business world. Once her mother decided to run for the presidency in 2007, however, Chelsea made hundreds of public appearances, mostly on college campuses, to support the campaign. More recently, she has worked for New York University and promoted her father’s latest book. She is currently pursuing a doctor’s degree at Oxford.

Clinton is the second daughter of a president hired by NBC News; Jenna Bush Hager, daughter of former President George W. Bush, works as a correspondent for NBC’s “Today” show.

小题1: Chelsea Clinton continued to stay out of media attention to _____.

A.improve the lives of others

B.help her father in the election

C.study and go to the business circle

D.support her mother for the presidency小题2: What does the underlined word mean in Paragraph 2?

A.is shown

B.flows

C.is managed

D.spreads小题3: Which is the right order of the events?

a. Chelsea helped to sell Bill Clinton’s latest book.

b. Chelsea pursues her doctor’s degree.

c. Chelsea supported her mother’s career.

d. Chelsea was out of the public attention.

A.d, a, c, b

B.c, d, b, a

C.c, b, d, a

D.d, c, a, b小题4: According to the text, we can conclude that _____.

A.Chelsea Clinton is the second daughter of Bill Clinton

B.Chelsea Clinton is in favour of her parents’ careers

C.Chelsea Clinton always follows her mother’s advice

D.Jenna Bush Hager is a correspondent for “NBC Nightly News”

单项选择题