《那些古怪又讓人憂心的問題》第36期:冰球一擊(1)
HOCKEY PUCK
冰球一擊
Q. How hard would a puck have to be shot tobe able to knock the goalie himself backward into the net?
Q．如果你想擊出一顆冰球並指望它把對面守門員一起撞進球網裏，那麼你得花多少力氣？
A. THIS CAN'T REALLY HAPPEN.
A．這不可能發生。
It's not just a problem of hitting the puckhard enough. This book isn't concerned with that kind of limitation. Humanswith sticks can't make a puck go much faster than about 50 meters per second,but we can assume this puck is launched by a hockey robot or an electric sledor a hypersonic light gas gun.
這不僅僅是你能拿出多大的力氣去擊球的問題，這本書可不關心那種限制。一個地球人用一根棍子沒法擊出時速遠大於每秒50米的球，但我們總可以假設冰球是被一個冰球機器人，或者一個電動滑板，再或者是一個超音速輕氣炮發射出來的。
The problem, in a nutshell, is that hockeyplayers are heavy and pucks are not. A goalie in full gear outweighs a puck bya factor of about 600. Even the fastest slap shot has less momentum than aten-year-old skating along at a mile per hour.
這個問題說到底就是冰球運動員太重，而冰球太輕。一個穿戴全副裝備的守門員的重量是冰球的600倍左右，即便是以最快速度擊出的冰球的動量也不超過一個10歲小孩兒以每小時1.6千米的速度滑冰時的動量。
Hockey players can also brace pretty hardagainst the ice. A player skating at full speed can stop in the space of a fewmeters, which means the force they're exerting on the ice is pretty substantial.(It also suggests that if you started to slowly rotate a hockey rink, it couldtilt up to 50 degrees before the players would all slide to one end. Clearly,experiments are needed to confirm this.)
冰球運動員踩在冰面上也相當穩。一個全速滑行的運動員能在幾米距離內停下來，這意味着他與冰面之間的作用力相當可觀。（這同時說明如果你慢慢擡起冰球場的一邊，那麼傾角需要達到50度才能讓所有運動員滑到另一邊去。顯然，我們急需一場實驗來驗證這個說法。）
From estimates of collision speeds inhockey videos, and some guidance from a hockey player, I estimated that the165-gram puck would have to be moving somewhere between Mach 2 and Mach 8 toknock the goalie backward into the goal-faster if the goalie is bracing againstthe hit, and slower if the puck hits at an upward angle.
基於我對冰球視頻中碰撞速度的估計，以及我的一位玩冰球的朋友給我的一些幫助，我推算出一個165克重的冰球需要以2～8馬赫之間的速度運動才能使守門員被打進到網裏——如果守門員穩穩地站在冰面上，速度要更高些，如果以向上的角度擊打冰球的話速度會低一些。
Firing an object at Mach 8 is not, initself, very hard. One of the best methods for doing so is the aforementionedhypersonic gas gun, which is-at its core-the same mechanism a BB gun uses tofire BBs.
以8馬赫的速度發射一個物體本質上來說不是很困難，要實現它最好的方法就是前面所說的超音速氣炮，其實——就核心原理來說——它跟發射BB彈的BB槍沒有區別。
