题目

如图所示，A、B两滑块质量分别为2kg和4kg，用一轻绳将两滑块相连后分别置于两等高的水平面上，并用手按着两滑块不动。第一次是将一轻质动滑轮置于轻绳上，然后将一质量为4kg的钩码C挂于动滑轮上，只释放A而按着B不动；第二次是将钩码C取走，换作竖直向下的40N的恒力作用于动滑轮上，只释放B而按着A不动。重力加速度g＝10m/s2 ， 不计一切摩擦，则下列说法中正确的是（） A . 第一次操作过程中，滑块A和钩码C加速度大小相同 B . 第一次操作过程In this century the traditional American family is constantly faced with the threat of breakdown. Some sociologists suggest that one little-noticed cause may be the introduction of the TV dinner.Before the appearance of television sets, the American dinner was a big event for the family. In many homes, dinner time may be the only time when everyone got together. A typical dinner was usually in three stages. In the preparation stage, the children and Father frequently helped with setting while Mother put the last touches on the roast. In the eating stage, family members shared the day’s experiences and more than food was eaten. In this stage families got to know one another and made joint decisions around the dinner table, and thus the family unit was strengthened. In the cleaning-up stage, children or Father again gave their hands, so that their importance to the home community was clear. Unfortunately, all of these have been removed by a product-the television set.By the beginning of the 1980s, the typical American family dinner was just twenty minutes long. The speed-up of the once-leisurely experiences is clearly connected to the pace of modern life and maybe a model of the modern life is the TV dinners-meals designed to be eaten from the beginning to the end of a half-hour program. The once family affair has now become nothing more than the use of a fork and knife.【小题1】The underlined word in the second paragraph can be replaced by        A．bigB．importantC．combinedD．separate【小题2】In the past, Americans tended to          .A．spend more time eating their food at dinner tableB．eat more food than they have todayC．spend more time talking about their day’s experiences at dinner tableD．talk so much that they forgot to eat【小题3】The shortening of the dinner time in America is related to        .A．The TV programsB．the pace of modern lifeC．the wide use of electrical equipmentD．the popularity of fast food【小题4】. The best title for this passage might be       A．Talk at Dinner TableB．TV DinnerC．Pace of Modern LifeD．Problems Caused by TV