题目

如图所示，一长为L的长方形木块在水平地面上由静止开始以加速度a做匀加速直线运动，先后经过A、B两点位置，且通过A、B两点所用的时间分别为t1和t2 ， 求： （1） 木块分别通过位置A、B的平均速度大小； （2） 木块前端P点到达位置A时的瞬时速度； （3） 木块前端P在A、B之间运动所需的时间． Once there was a farmer who lived on a farm in Africa. One day, a wise man visited him and told him about the value of diamonds (钻石). He said, “If you had a diamond as big as your thumb (大拇指), you could have your own city. If you had a diamond as big as your fist (拳头), you could probably have your own county.”That night the farmer couldn’t sleep well. He was very unhappy because he was not satisfied with what he had. He wanted to become rich. The next morning he sold his farm to a man and went to look-for diamonds. He travelled all over Africa, Europe and America, but couldn’t find any diamonds. He became so sad that he threw himself into a river and died.Two years later, the man who had bought the farmer’s farm found a stone on the farm. He put the stone on a shelf in the living room. One day the wise man visited him and saw the stone. He checked the stone carefully and said that it was a diamond. The man was happy and excited because there were many “stones” on the farm.So you see that sometimes what you want is always by your side, but you don’t realize its value.【1】Why couldn’t the farmer sleep well?A.Because the wise man left.B.Because his farm was sold.C.Because he couldn’t find any diamond.D.Because he wanted to be rich.【2】The diamonds were found by the man in ________.A.AfricaB.EuropeC.AmericaD.Asia【3】What’s the right order of the story?①The farmer couldn’t find any diamonds and killed himself.②A wise man told the farmer that diamonds are valuable.③The man sold his farm and went out for diamonds.④The man who had bought the farm found lots of diamonds on the farm.A.②③④①B.②③①④C.③①④②D.③④②①【4】The writer wants to tell us that ________.A.we must try our best if we want to succeedB.life is valuableC.we should realize the value of what we haveD.we can be rich by accident