用一轻绳将小球P系于光滑墙壁上的O点，在墙壁和球P之间夹有有一矩形物块Q。P、Q均处于静止状态，则下列相关说法正确的是（ ）
A．P物体受4个力
B．Q受到3个力
C．若绳子变长，绳子的拉力将变小
D．若绳子变短，Q受到的静摩擦力将增大
AC
题目分析：单独分析Q受力如图，Q受自身重力G，墙壁支持力N和球的压力N1，由于墙壁光滑，没有摩擦力，要使Q静止必须有竖直向上的力，因此P对Q有竖直向上的摩擦力f而且大小等于Q的重力答案D错。因此Q受力为4个。B错，分析P受力，除自身重力G和Q对其压力外，根据相互作用还有Q对其竖直向下的摩擦力f和绳子的拉力F 共计4个力，A对。整体受力分析如图，共有绳子拉力，PQ重力和墙的弹力，根据力的合成，重力和弹力合力与拉力等大反向如图，绳子越长，
越小，拉力F越小，答案C对。
书面表达（共两节，满分45分）
阅读下面短文, 请根据短文后的要求进行答题。（请注意问题后的字数要求） [1]World Consumer Rights Day is celebrated annually by consumer organizations worldwide. It commemorates the historic declaration on March 15, 1962 by John F. Kennedy, the former U.S. President, of the basic Rights of consumers, which include: "the right to safety", "the right to be informed", "the right to choose", and "the right to be heard". [2]This declaration has led to international recognition by governments and the United Nations that all citizens, regardless of their incomes or social standing, have certain basic Rights as consumers. Officially, World Consumer Rights Day was first observed on March 15，1983 and has since become an important occasion for mobilizing citizen action, with recognition of consumer rights taking off around the world. On April 9，1985, the United Nations Assembly General Assembly adopted the UN Guidelines for Consumer Protection that provide a framework for strengthening national consumer protection policies around the world. [3]The guidelines included Kennedy's four basic consumer rights plus another four: the right to satisfaction of basic needs; the right to redress(赔偿); the right to education; and the right to a healthy environment. Currently, the fundamental consumer rights are recognized globally. [4]World Consumer Rights Day normally has a theme associated with an activity or development that is relevant to consumers. Whatever their objectives, they share the same underlying aim of bringing about important and needed benefits for consumers. [5]In recent years, progress has been made for recognition and protection of consumer rights in developing countries. At least, March 15 is a day when consumers are filled with pride and satisfaction. However, there are many reports on violation of consumer rights by unethical marketing practices. 76. What is the main idea of the passage? (Please answer within 10 words.) _______________________________________________________________________________ 77. What was John F. Kennedy mentioned in the first paragraph? (Please answer within 15 words.) _______________________________________________________________________________ 78. Which of the sentence in the passage can be replaced by the given one? Presently, countries around the world acknowledge the basic consumer rights. ______________________________________________________________________________ 79. Please translate the underlined sentence in the second paragraph into Chinese. ______________________________________________________________________________ ______________________________________________________________________________ 80. What do you think will follow the passage? (Please answer within 20 words.) ______________________________________________________________________________ ______________________________________________________________________________ 第一节：阅读表达（每小题3分，合计15分） |