时差N小时:哪一个先落地?(上)

Here’s a physics classic. Suppose you drop a golfball and a bowling ball from the Empire StateBuilding. Which hits first? Answer? They hit at thesame time. You could also have used a marble and apiano and a banana, or any two objects for which airresistance won’t be a big factor. The idea is thateverything falls at the same rate, no matter what itsmass is. A lot of folks have trouble believing this. Itjust doesn’t seem right. Oftentimes we say, “But abowling ball weighs more than a golf ball — doesn’tthat mean gravity is pulling on it more?” Well,there’s a distinction to be made here. The bowling ball has a greater mass, so there’s morestuff for gravity to act on. In that sense, gravity is pulling on it more. But it still doesn’t fallany faster.

这是一个物理学的经典：设想你从帝国大厦上同时丢下一个高尔夫球和一个保龄球。那个先着地?答案?它们同时着地。你也可以换成弹子，钢琴或是香蕉，或任意2个受空气阻力影响不大的物体。任何物体都会以相同的速度落地，无论质量多大。许多人不太相信这个规律。这个规律只是看起来不对。我们经常会说“但是保龄球要比高尔夫球重很多——那并不表明重力会更多作用于较重的物体吗?这里要说明下区别。保龄球的质量更大，所以引力作用的面积会更多。那样的话，引力会更大，但是物体落下的速度并没有变快。

classic n. 杰作 marble n.弹子 facto n.因素 distinction n.区别