问题 选择题

如图3所示,用弹簧测力计水平拉动水平桌面上的物体,使其作匀速直线滑动。以下叙述中的两个力属于一对平衡力的是(    )

A.弹簧测力计对物体的拉力与物体所受的重力

B.弹簧测力计对物体的拉力与桌面对物体的摩擦力

C.物体对桌面的压力与桌面对物体的支持力

D.物体对桌面的压力与物体所受的重力

答案

答案:B

因为物体在水平桌面上做匀速直线运动,而物体在水平方向受弹簧测力计的拉力和桌面对物体的摩擦力作用,在竖直方向上物体受重力和桌面对物体的支持力作用;由二力平衡的条件可得:弹簧测力计对物体的拉力和桌面对物体的摩擦力为一对平衡力,物体的重力和桌面对物体的支持力为一对平衡力.

故选 B.

单项选择题 A型题
阅读理解

●The first double hand transplant patient in the US has left a hospital after medicine cleared up

small red spots on his skin that signaled he might be rejecting his new hands. Jeff Kepner, a 58-year-old former chief cook in a restaurant, lost his hands and feet a decade ago to a bacteria infection. The donor was a 23-year-old man.

●A second major storm in less than a week was blowing yesterday toward the Washington area, where federal government offices were closed for a second day and workers struggled to restore power knocked out by a weekend heavy snowstorm. The storm could leave as much as 20 inches (50 centimeters) of new snow in Washington and nearly as much near Philadelphia –a Northeast travel-hub by tonight.

●British Prime Minister Gordon Brown will give evidence to a public inquiry into the Iraq War in early March, officials for the inquiry said yesterday. Brown’s appearance, just weeks before an election expected in May, could hit the ruling Labour Patry’s attempts to catch up in the polls (民意调查)behind the opposition party Conservatives. Brown, who will be questioned about his time as prime minister, will be a witness in the highest position at the inquiry since former Prime Minister Tony Blair’s appearance last month.

●The head of the UN agency aiding Palestine refugees (难民)is warning a funding shortfall and appealing for another $100 million. Filippo Grandi says the money is necessary for education, health and social services for 4.7 million Palestinian refugees scattered across Jordan, Syria, Lebanon, the West Bank and the Gaza Strip. The agency’s 2010 budget is $620 million, and it expects a shortfall of $140 million. The agency says $100 million is necessary for basic services.

64.The passage is most probably adapted from        .

A.new items in a newspaper       B.descriptions of the world situation

C.discussions on foreign affairs  D.statements of a government report

65.It can be inferred from the passage that        .

A.the man lost his hands for an unknown reason

B.the result of the transplant operation seems satisfying

C.another storm will hit Washington area in less than a week

D.the electricity supply was cut off in Philadelphia a week ago

66.According to the passage, Gordon Brown          .

A.is the leader of the ruling Labour Party in Britain

B.will send army to the Iraq War in March this year

C.will compete with former Prime Minister Tony Blair

D.is now gaining more support from voters than others

67.Which of the following statements is TRUE according to the fourth news?

A.$100 million should be needed for the survival of the refugees.

B.At least $100 million is to be raised for Palestinian refugees.

C.The refugees mentioned in the passage are in the Middle Africa.

D.It is a tough job for the UN agency to get money for the refugees.