题目

阅读下列材料，在空白处填入适当的内容（1个单词）或括号内单词的正确形式。Yangshuo, China It was raining lightly when I (arrive)in Yangshuo just before dawn. But I didn't care. A few hours I'd been athome in Hong Kong, with (it) choking smog. Here, the air was clean andfresh, even with the rain. I'd skipped nearby Guilin, a dream placefor tourists seeking the limestone mountain tops and dark waters of the LiRiver are pictured by artists in so many Chinese (painting).Instead, I'd headed straight for Yangshuo. For those who fly to Guilin, it'sonly an hour awa如图所示，一质量为M的小车置于光滑水平面上，小车两侧壁均固定长度为l的弹性物质。将质量为M的光滑物块放到小车上，物块与小车右侧的弹性物质接触但不连接。现将小车固定，在外力作用下推动物块压缩弹性物质，弹性物质压缩到一定程度后，同时释放小车和物块。由小车之外的固定传感器获得小车对地运动的加速度大小与时间的a-t图象如图所示(图象中数据为已知量，弹性物质始终在弹性限度内)。求：(1)外力压缩弹性物质所做的功；(2)小车的实际长度。