题目

物体从静止开始做直线运动的v-t图像如图所示，则该物体A.在第8s末相对于起始点的位移最大B.在第4s末相对于起始点的位移最大C.在第2s末到第4s末这段时间内的加速度最大D.在第4s末和第8s末处于同一位置 答案：【答案】D【解析】AB.由图可知，6s内物体一直沿正方向运动，6-8s时物体反向运动，故第6s末时相对于起点的位移最大，故A错误，B错误；C.图象的斜率表示物体的加速度，由图可知，4-8s内图线的斜率最大，加速度最大，故C错误；D.根据图象与坐标轴围成面积代表位移，时间轴上方位移为正，时间轴下方 任务型阅读：根据短文内容回答问题 　　On Sunday,April 22,people all over the world take time out to appreciate(珍惜)the earth that we all share．It's Earth Day,a special day to learn about our planet(星球)and how to take care of it． 　　On Earth Day,some people listen to speeches about the environment．Others help clean up their offices or save water and electricity at home．Your parents many even decide to take a day off from driving their cars． 　　The idea for Earth Day came from a U.S.Senator(参议员),who was worried about pollution and the health of plants and animals．And the idea quickly caught on(流行起来)．In 1970,the first Earth Day was celebrated．More than 20 million people in cities all over the U.S.took part．Since then, Earth Day has been used to educate people about their role in taking care of our planet． 　　Now,Earth Day has become a global celebration．In 1990,200 million people from 140 countries took part in clean-ups,tree planting and other environmental events on Earth Day．(1) When is EarthDay? (2) Who came up with the idea for Earth Day? (3) How many people celebrated the first Earth Day in 1970? (4) Is Earth Day popular around the world now? (5) What is Earth Day?