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.
有一些超级英雄可以跑得比风还快 在阿波罗10号载人航天器里的人们达到了这个速度 达到了这个打破了纪录的速度 大约25,000英里每小时 当载人航天器再次进入地球大气层的时候 那是在1969年 我们将节约很多时间 如果我们能像他们一样快 但是,这样做有没有什么不利之处? 空气中并不是什么都不存在的 像氧,氮这样的元素 甚至数不尽的灰尘颗粒 组成了我们周围的空气 当我们穿过空气中的这些物质时 我们在摩擦它们 因此出现了一些摩擦力 导致了温度的上升 就像你搓手可以使手暖和起来 或者钻木取火 物体摩擦的越快 温度上升的高 因此,如果我们以每小时25,000英里每小时的速度奔跑 摩擦引起的温度上升会烧掉我们的脸 即使我们通过某种方式承受住了这种温度 空气中的沙粒和尘埃将同时向我们袭来 会将我们刮伤 带来无数的 小创口 你有没有观察过汽车的前保险杠? 你认为那些飞着的鸟和虫子 会对你睁着的眼或者暴露在外的皮肤产生什么样的伤害? 那么,假如你戴着一张面具 来避免对脸部的伤害 然而,那些在你和你的目的地之间的 人和建筑呢? 从看见信号到作出反应 我们大概要用1/5秒 从我们看见我们面前的东西 到我们作出反应 时间 x 速度 = 距离 = 1/5秒x=1.4英里 25,000英里每小时 =1.4英里 我们可能已经路过 或者穿过它们并且又走了一英里 我们可能杀死了自己 因为我们以巨大的速度撞上了离我们最近的墙 也有可能,更糟糕一些,如果我们不会被摧毁,而继续跑下去 我们的身体就好像变成了导弹 摧毁沿途的所有物体 因此,以25,000英里每小时的长距离旅程 会使我们烧焦 我们会撞上许多的虫子 并且没有反映的时间 那么,短程的奔跑 把我们可以看到的地方作为目的地 并且途中没有障碍物,这样可行么? 假设有一枚子弹 马上就要击中一个不幸的美丽少女 所以,我们的英雄要以巨大的速度 来个英雄救美 并把她带到安全地带 这一切听起来很浪漫 但是,事实上,相比起被子弹射中 带着少女以巨大的速度移动 可能会使少女受到更多伤害 牛顿第一运动定律也被称为惯性定律 它是关于物体应对改变其原有的运动状态的 抵抗性的阐述 因此,一个物体会继续移动 或者保持静止 除非有什么改变了它 加速度是速度在单位时间内的改变量 当那位少女静止的时候 也就是说她的速度是零 然后,她开始加速,在几秒内就达到了25,000英里每小时 速度增长的非常快 直到她达到那个速度才停止 由于惯性,她的大脑会撞上她头骨的一侧 而且,当她突然停下来的时候 速度减小的非常快直到速度减到了零 这时,他的大脑就会撞击她头骨的另一侧 她的大脑也因此变成“一团浆糊” 所以我们的大脑非常脆弱以至于无法应对突如其来的运动 我们身体上的别的器官也是这样,也可能发生类似的事 记住,并不是巨大的速度带来的伤害 因为阿波罗10号里面的宇航员都活着回来了 是加速度 或者突然停止 引起我们身体内部的器官 撞上了它前面的什么东西,我们身体的另一部分 就像我们在坐公共汽车时 当司机踩刹车的时候 那个英雄救美的行为 在数学意义上相当于以载人航天器的最大速度 撞上了她 由于巨大的冲击,她很可能当场死亡 这样的话,这个英雄就欠这个可怜少女的家人一次道歉 和一笔巨大的赔款 对了,也有可能面对牢狱之灾 医生必须要买责任保险 以免他们误伤了患者 我很想知道超级英雄们会花多少钱来买保险 现在,你将继续 参加哪一种超能力的物理课 迅速改变身体的大小 超快的速度 飞行 力大无穷 长生不老 亦或是 隐身