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.
Nekateri super junaki so hitrejši od vetra. Možje v Apollu 10 so dosegli rekordno hitrost okoli 40.000 km/h, ko se je plovilo leta 1969 vrnilo v Zemljino atmosfero. Mar ne bi prihranili veliko časa, če bi se lahko tako hitro premikali? V čem je problem? Zrak ni prazen. Elementi, kot sta kisik in dušik, celo nešteto prašnih delcev sestavljajo zrak okoli nas. Ko se premikamo skozi vse to, se drgnemo ob delce in ustvarjamo veliko trenja, kar povzroči segrevanje. Tako kot roke ogrejemo z drgnjenjem in s trenjem palic prižgemo ogenj, hitreje ko to poteka, več toplote nastane. Če bi tekli s hitrostjo 40.000 km/h, bi nam vročina zaradi trenja sežgala obraz. Tudi če bi nekako prenesli vročino, bi pesek in umazanija v zraku povzročila odrgnine, naenkrat bi dobili milijone majhnih ureznin. Ste kdaj videli prednji odbijač tovornjaka? Kaj mislite, da bi ptice in žužki naredili odprtim očem in goli koži? V redu, imeli boste masko, da si ne uničite obraza. Kaj pa ljudje v stavbah med vami in vašim ciljem? Okoli petino sekunde traja, da reagiramo na to, kar vidimo. Preden bi videli, kaj je pred nami, in na to reagirali - čas krat hitrost je razdalja, petina sekunde krat 40.000 km/h je 2,3 km - bi bili že mimo ali skozi in to za več kot 1,5 km. Verjetno nas bo ubilo, saj se bomo noro hitro zaleteli v kak zid, če pa smo neuničljivi, bomo telesa spremenili v izstrelke, ki bodo uničili vse pred sabo. Dolga pot s hitrostjo 40.000 km/h bi nas sežgala, pokrila z žužki in nam ne bi dala časa za odziv. Kaj pa kratki skoki do kraja, ki ga vidimo, brez vmesnih ovir? Recimo, da bo naboj zadel lepo dekle v težavah. Naš junak prileti z veliko hitrostjo, jo ujame in odnese na varno. To zveni zelo romantično, a verjetno bo junak dekle bolj ranil kot bi jo naboj, če se bo vanjo zaletel s super hitrostjo. Prvi Newtonov zakon gibanja govori o inerciji, ki je odpornost na spremembe v gibanju. Predmet se bo gibal ali ostal na istem mestu, če tega nič ne spremeni. Pospešek je delež spremembe hitrosti skozi čas. Ko bi mirujoče dekle s hitrostjo nič km/h začelo pospeševati, bi hitrost poskočila na 40.000 km/h in njeni možgani bi se zaleteli v zadnji del lobanje. In ko bi se nenadoma ustavila, bi hitrost padla na ničlo in možgani bi skočili na drug konec lobanje ter postali ena sama kaša. Možgani so preveč krhki za nenadne gibe. To pravzaprav velja za vsak del telesa. Zapomnite si, poškodba ni zaradi hitrosti, saj so astronavti preživeli let Apolla 10, težava je v pospešku ali nenadni ustavitvi, zaradi česar notranji organi zadenejo prednji del telesa, kot nas odnese v avtobusu, ko voznik močno pritisne na zavoro. Junak je, matematično gledano, dekletu povzročil nekaj podobnega, kot če bi jo zadel z vesoljskim plovilom pri največji hitrosti. Verjetno je umrla takoj ob udarcu. Moral se bo opravičiti njeni družini in prinesti velik ček, da se oddolži. In verjetno bo šel v zapor. Zdravniki morajo biti zavarovani za primere, če naredijo napako in poškodujejo pacienta. Sprašujem se, koliko bi stala zavarovalna polica za super junake. Katero nadnaravno moč boste raziskali zdaj? Spreminjanje velikosti in sestave telesa, super hitrost, letenje, nadnaravno moč, nesmrtnost in nevidnost.