题目

甲乙两个物体在同一直线上运动的s-t图象如图2所示，以甲的出发点为原点、出发时刻为计时起点，则由图象可以看出     （     ）A.甲乙同时出发B.乙比甲先出发C.甲开始运动时，乙在甲前面s0处D.甲在中途停了一会儿，但最后还是追上了乙 答案：ACD【试题分析】由图2可以看出：甲在t1时间内做匀速运动,然后在t1到t2时间内处于静止状态,从t2时刻之后做匀速直线运动.乙物体一直做匀速直线运动.甲乙两物体同时出发但出发地点不同，乙物体从正向s0处出发．t3时刻两图线相交，表示两物体处在同一位置，即甲追上乙.I always experienced guilt when I passed by without giving a coin or two to a beggar.My conscience was pricked again on a tour of Venice in 2010. I had taken refuge from the crowds in a quiet canal-side café. Outside the café was an old woman kneeling on the ancient cobbled stones, begging. Steady streams of tourists were walking past her. A lone young back-packer stood away from the crowds drinking something, but I noticed he was also observing the woman.A tourist group glanced at the woman and walked on. Another group of tourists arrived and, again, walked past her. The backpacker watched. Then, as I prepared to leave, I stopped at the sight of the backpacker stepping forward and placing some money in the woman’s cup. He did this rather ostentatiously（炫耀地）, just before the arrival of another tourist group. I watched as the leader of the group stopped and put some money in the cup. Having been shown the way, other tourists followed suit and added more coins to the woman’s cup.The young backpacker repeated this process in front of the next tour party going past. Once again, the subtle peer （同伴）pressure worked on the tourists, who all added coins to the cup. His work done, the young man walked over to the old beggar woman, patted her shoulder and said, “I hope that helps a bit.”I don’t know if the woman understood his English or realized what had just happened, but I did. I placed some money in the woman’s cup and continued my travels, light-hearted after witnessing such an act of caring.1.The backpacker placed some money in the woman’s cup rather ostentatiously because______.A. he wanted to stop the tourists by doing thisB. he wanted people to know that he was rich and kindC. he wanted to help the woman by himselfD. he wanted the tourist group to follow him2.The author went to a quiet canal-side cafe to_______ .A. avoid meeting the beggarB. get away from the crowdsC. take a restD. watch the woman beggar3.We can infer from the passage that ________ .A. tourists can be cheated by beggarsB. people usually have pity on an old beggarC. tourists are willing to help beggarsD. people can do kind acts due to peer pressure4.Before the backpacker dropped some money in the woman’s cup, the tourists ______ .A. all showed pity for the womanB. didn’t notice the womanC. walked by without giving any moneyD. gave a little money to the woman