物理学史上最美的十个实验第八名.doc

物理学史上最美的十个实验第八名
Galileo's experiments with rolling balls down inclined planes
 伽利略的斜面滚球实验

   Galileo continued to refine his ideas about objects in motion. He took a board 12 cubits long and half a cubit wide and cut a groove, as straight and smooth as possible, down the center. He inclined the plane and rolled brass balls down it, timing their descent with a water clock — a large vessel that emptied through a thin tube into a glass. After each run he would weigh the water that had flowed out — his measurement of elapsed time — and compare it with the distance the ball had traveled.

   Aristotle would have predicted that the velocity of a rolling ball was constant: double its time in transit and you would double the distance it traversed. Galileo was able to show that the distance is actually proportional to the square of the time: Double it and the ball would go four times as far. The reason is that it is being constantly accelerated by gravity.

伽利略继续提炼他有关物体移动的观点。他拿了一块大约六米长，廿五厘米宽的木板，中间挖了一个平滑的沟槽。他先将木板斜放，将许多铜球沿沟槽滑下，再用水鐘计算球落下的时间。铜球滑行的距离各有不同，最后一一比较。
亚里士多德曾预言滚动球的速度是均匀不变的：铜球滚动两倍的时间就走出两倍的路程。伽利略却证明铜球滚动的路程和时间的平方成比例：两倍的时间里，铜球滚动4倍的距离，因为存在恒定的重力加速度。