题目

You may not pay much attention to your daily elevator(电梯) ride. Many of us use a lift several times during the day without really thinking about it. But Lee Gray, PhD, of the University o f North Carolina, US, has made it his business to examine this overlooked form of public transport. He is known as the “Elevator Guy”.    “The lift becomes this interesting social space where etiquette (礼仪) is sort of odd (strange),” Gray told the BBC. “They [elevators] are socially very interesting but often very awkward places.”    We walk in and usually turn around to face th“频闪摄影”是研究物体运动时常用的一种实验方法,如图-6是小严同学利用频闪照相机拍摄的不同物体运动时的频闪照片(黑点表示物体的像),其中可能做匀速直线运动的是(　　)A. B. C. D. B 【解析】A. 图中相邻两个黑点之间的距离逐渐减小，说明物体做减速直线运动；故A符合题意；B. 图中相邻两点间的距离相等，说明物体做匀速直线运动，故B不符合题意；C. 图中相邻两个黑点之间的距离逐渐增大，说明物体做加速直线运动，故C符合题意；D. 图中相邻两个黑点之间的距离尽管相等，但是运动的轨迹是曲线，说明物体做曲线运动，故D符合题意。故选B.