【英语时差8,16】冒失的跌倒

Ya?l: It's time to go again to the A Moment of Science mailbag.

Don: A listener writes:

     Dear A Moment of Science,  I'm a big baseball fan, and I've always wondered why some players slide feet first and some slide headfirst. Does either way provide an advantage?

Y: Great question! And the answer depends on what sort of advantage you're looking  for. If you want to be able to jump up quickly after sliding into a base, then feet first is best. But if speed is what you need, then headfirst might be better.

D: At least according to a thought experiment in basic physics. When a player slides, he's basically rotating around his center of gravity, located somewhere near the hips¹ and waist. Slide feet first and the body rotates clockwise. Slide headfirst and the body rotates counter-clockwise.

Y: But because the arms are typically lighter² than the legs, sliding headfirst creates a  faster rotation³, which should allow a runner to touch the base more quickly. Plus,   sliding headfirst allows the runner to push off with his feet, providing an extra bit of  momentum.

D: Now, the few studies to actually test this hypothesis have found no significant  advantage to headfirst sliding. But the studies were small and don't prove that the  headfirst technique isn't faster. It could have a lot to do with technique. Because  coaches fear that sliding headfirst can lead to hand and finger injuries, many don't  teach young players the art of the headfirst slide. Landing awkwardly before reaching  base will slow you down.

Y: But when done properly, a headfirst slide might be faster.  

1 hips   

abbr.high impact polystyrene 高冲击强度聚苯乙烯，耐冲性聚苯乙烯n.臀部( hip的名词复数 )；[建筑学]屋脊；臀围（尺寸）；臀部…的

参考例句：

• She stood with her hands on her hips. 她双手叉腰站着。
• They wiggled their hips to the sound of pop music. 他们随着流行音乐的声音摇晃着臀部。 来自《简明英汉词典》

2 lighter   

n.打火机，点火器；驳船；v.用驳船运送；light的比较级

参考例句：

• The portrait was touched up so as to make it lighter.这张画经过润色，色调明朗了一些。
• The lighter works off the car battery.引燃器利用汽车蓄电池打火。

3 rotation   

n.旋转；循环，轮流

参考例句：

• Crop rotation helps prevent soil erosion.农作物轮作有助于防止水土流失。
• The workers in this workshop do day and night shifts in weekly rotation.这个车间的工人上白班和上夜班每周轮换一次。