题目

短文改错Many people may have heard a plant that we call it tortoiseshell bamboo. This bamboo can grow so tall as 28 meters. This particular species are the most commonly used material in China's industry. Before it is planted, no obviously growth occurs for up to five years—even under ideal conditions! Then, as if by magic, a plant suddenly begins to grow at the rate of nearly 70 centimeters per day, reached its full height within six weeks. Besides, it's not magic. The bamboo's rapid growth resulted from the miles of roots it develops during those first five years, five years of getting小华的奶奶因地板太滑而摔倒了，于是小华想换一种防滑效果好的木地板．他和同学小强从市场上找来较为常用的A型和B型两种木地板的样板，小华认为要比较防滑效果也就是比较哪种地板表面更粗糙，于是小华将样板倒放在水平桌面上，进行了如图甲和乙的实验．（1）两次实验都要使木地板样板在水平桌面上做______运动，这样做的目的是使滑动摩擦力大小______拉力大小．（选填“大于”、“等于”或“小于”）（2）小华根据两次示数F1＜F2，由此得出结论：B型木地板表面更粗糙．你认为他的探究过程中存在的问题是______．（3）小强受研究牛顿第一定律实验的启发，他找来一个斜面和一个小车，设计了如图丙所示的实验，让小车从斜面上滑到这两种木地板平面上，他想根据小车在这两种木地板平面上滑行距离的远近，来比较哪种木地板表面更粗糙．请说明使用这种方法进行实验时的操作要点：______．