Some superheros can move faster than the wind. The men in Apollo 10 reached a record-breaking speed of around 25,000 miles per hour when the shuttle re-entered the Earth's atmosphere in 1969. Wouldn't we save a lot of time to be able to move that fast? But what's the catch? Air is not empty. Elements like oxygen and nitrogen, even countless dust particles, make up the air around us. When we move past these things in the air, we're rubbing against them and creating a lot of friction, which results in heat. Just like rubbing your hands together warms them up or rubbing two sticks together makes fire, the faster objects rub together, the more heat is generated. So, if we're running at 25,000 miles per hour, the heat from friction would burn our faces off. Even if we somehow withstood the heat, the sand and dirt in the air would still scrape us up with millions of tiny cuts all happening at the same time. Ever seen the front bumper or grill of a truck? What do you think all the birds and bugs would do to your open eyes or exposed skin? Okay, so you'll wear a mask to avoid destroying your face. But what about people in buildings between you and your destination? It takes us approximately one-fifth of a second to react to what we see. By the time we see what is ahead of us and react to it - time times velocity equals distance equals one-fifth of a second times 25,000 miles per hour equals 1.4 miles - we would have gone past it or through it by over a mile. We're either going to kill ourselves by crashing into the nearest wall at super speed or, worse, if we're indestructible, we've essentially turned our bodies into missiles that destroy everything in our path. So, long distance travel at 25,000 miles per hour would leave us burning up, covered in bugs, and leaves no time to react. What about short bursts to a location we can see with no obstacles in between? Okay, let's say a bullet is about to hit a beautiful damsel in distress. So, our hero swoops in at super speed, grabs her, and carries her to safety. That sounds very romantic, but, in reality, that girl will probably suffer more damage from the hero than the bullet if he moved her at super speed. Newton's First Law of Motion deals with inertia, which is the resistance to a change in its state of motion. So, an object will continue moving or staying at the same place unless something changes it. Acceleration is the rate the velocity changes over time. When the girl at rest, velocity equals zero miles per hour, begins accelerating to reach the speed within seconds, velocity increases rapidly to 25,000 miles per hour, her brain would crash into the side of her skull. And, when she stops suddenly, velocity decreases rapidly back to zero miles per hour, her brain would crash into the other side of her skull, turning her brain into mush. The brain is too fragile to handle the sudden movement. So is every part of her body, for that matter. Remember, it's not the speed that causes the damage because the astronauts survived Apollo 10, it's the acceleration or sudden stop that causes our internal organs to crash into the front of our bodies the way we move forward in a bus when the driver slams on the brakes. What the hero did to the girl is mathematically the same as running her over with a space shuttle at maximum speed. She probably died instantly at the point of impact. He's going to owe this poor girl's family an apology and a big fat compensation check. Oh, and possibly face jail time. Doctors have to carry liability insurance just in case they make a mistake and hurt their patients. I wonder how much superhero insurance policy would cost. Now, which superpower physics lesson will you explore next? Shifting body size and content, super speed, flight, super strength, immortality, and invisibility.
有些超級英雄能移動得比風速還快 1969年阿波羅十號 重返地球表面時 在太空梭裡的人即達到 每小時約兩萬五千哩 破紀錄的移動速度 假如我們能移動得這麼快 不是省下了很多時間嗎? 但這有何內幕呢? 空氣並非無雜質 像是氧及氮元素 甚至數不盡的塵埃微粒 組成了環繞四周的空氣 當我們移動時,會和空氣中這三樣物質 擦身而過 進而製造許多摩擦力 來產生熱能 就像是摩擦雙手取暖 或者摩擦兩根棍子取火 其摩擦的速度越快 就能產生越多熱能 所以如果我們每小時跑到兩萬五千哩 因摩擦力而產生的熱能會把我們的臉燒掉 即使人體能夠承受熱 空氣中的沙粒及塵土 仍會同時以 數百萬的微小切割 來刮傷我們的肌膚 曾看過前保險桿或燒烤的卡車嗎? 你覺得所有小鳥以及蟲子會如何對付 你那睜開的雙眼及曝露在外的皮膚呢? 好吧!你會因此戴上防護面具 來避免臉部遭受損害 但在你和目的地間 大樓裡的人們又會如何呢? 我們大約花五分之一秒的時間去對 自己看到的事物反應 在我們看見眼前事物的當下 就得做出反應 時間乘以速率等於距離 等於五分之一秒 乘以時速兩萬五千哩 等於一點四哩 我們會在超過一英哩處 即遭逢此劫 若不是以超高速度 來撞進距離最近的牆而殺了自己 或者,更糟的是,如果沒死 我們會把自己的身體變成導彈 摧毀行經道路的一切事物 因此,以時速兩萬五千哩長途旅行 會把自己燒成灰燼 會被各種蟲子衝撞 而且還沒時間反應 那麼短距離衝刺 到一個放眼所及 沒有障礙物的地方又如何呢? 這麼說好了! 一顆子彈快要打到一位漂亮、需要幫助的女子 而我們的英雄以超高速俯衝 去抓住她 把她帶到安全的地方 聽起來很浪漫 但事實上,這女孩可能會因英雄 的快速移動而遭受比起子彈 更大的損傷 牛頓第一運動定律,慣性定律 是對運動狀態變化 的抵抗 除非被外力改變 否則物體會持續移動 或待在相同地方 加速是速率隨著時間的改變 當這女孩休息時 時速靜止不動 在數秒內開始加速到達一定速度 速率快速增加 到每小時兩萬五千哩 她的大腦會被擠壓到頭骨邊緣 而當她突然停下來 速率快速回歸於零 她的大腦會被擠壓到另一邊頭骨邊緣 把大腦變成糊狀 大腦太脆弱,以致無法承受快速運動 同樣的,身體任何部位也是如此。 記住,那並不是速度所造成的損害 因為阿波羅十號裡的太空人是活著的 是加速 或突然靜止 造成我們內部器官 擠壓到身體前端 就像公車司機猛踩煞車時 我們的身體會往前推移 這英雄帶著女孩 的快速移動,在數學上相當於搭乘太空梭 到達極大速度 她很可能會在碰撞時當場死亡 英雄將欠下這可憐女孩的家人一個道歉 以及龐大的賠償費用 可能還得面對牢獄之災 醫生們必須肩負起責任保險 以防萬一誤診而傷了病患 我想知道超級英雄的保單費用會有多高 那麼,你下一個想要探索的 超能力物理課是甚麼呢? 調整身體大小及內容 超高速 飛行 超力量 長生不死 和 隱形