Mankind likes big things. We like gigantic iPhones, Venti Lattes, and skyscrapers. The pyramids of Egypt represent perhaps man's earliest obsessions with making big things. As children, we stack wooden blocks until they topple and injure the cat. We are a species obsessed with bigness. But how big could we build? The current tallest building in the world is pretty big, but it's miniscule compared to the towering peak of Mt. Everest. The world's tallest buildings keep getting bigger, but eventually there comes a point when it is impossible to keep building upward. Or is there? In 1895, Konstantin Tsiolkovsky proposed a structure known as a space elevator. Such a structure would begin on Earth and stretch all the way out into outer space. But wouldn't it crumble under its own weight? Normally yes, but this isn't your average game of Jenga. A structure in orbit experiences an apparent centrifugal force that increases the farther out in space an object gets. How and why demands a separate blog post, but given that parameter, a structure as tall as a space elevator would be able to support its own weight because the top section would experience a net force outward that cancels out the gravity that would cause the structure to topple. Therefore, it would theoretically be possible to create a space elevator. Unfortunately, there would still be a ton of forces involved, making most materials useless. However, scientists have postulated that carbon nanotubes might be strong enough to be used in such a project. Even so, the space elevator is a long ways away, but should it come to fruition, it would make transporting packages into space immensely less expensive. Plus, it would probably look awesome.
Last weekend I attended the high school's production of All Shook Up. It was a nice show but a few things stood out to me. The first was that the string of lights they used in the abandoned fairgrounds scene was wired in parallel. Some of the lights were out, but the rest still shone on, because there was still a path for current to get from one bulb to the other, whereas in a series configuration, a dead bulb would block all current flow and cause the all of the remaining bulbs to go dark. Props to the mayor from springing for the nicer lights. Maybe I can use this as leverage for my mother to finally get better Christmas lights. Another thing I noticed was a sign posted on an outside wall of the school. The sign said something to the effect of "security cameras may or may not be monitored at any time." Of course, my "sign language" skills are not the best, so some of the effect is lost in translation. However, the sign did make me wonder: if it is impossible to know whether a security guard is watching the cameras, then does that mean they exist in a superimposition of both states à la Schrodinger's cat? It has essentially the same setup, as we cannot know if the cameras are being monitored without "opening the box." Perhaps the sign should say, "security cameras are both monitored and not monitored at all times." But the real question here is, does the security guard get paid for all that time he was both working and not working? These are the problems imposed by quantum physics.
If you've ever driven late at night with an irresponsible teenage driver, you've most likely involuntarily been a part of some pretty crazy car stunts. The good old fashioned Tokyo drift and doughnut are classic examples of things that should not be done with a car. But like most things that are bad for you, they are pretty cool. A stunt that doesn't get a lot of love is the wheelie. It's one thing to pop one on a bike or a Razor scooter, but to do it with a four-wheeled car is on a whole other level. Of course, it's too dangerous and also impossible for non-professional drivers, but how is it done? Well the most important part of popping a wheelie is to get tons of torque on the rear axle. By accelerating the car forward at a great rate, a torque is applied that counteracts the torque provided by the center of mass of the car. Once the torque gets great enough, the front axle bears none of the weight of the car and begins to tip upward. Motorcycles are easier to wheelie because they are shorter, making their center of mass closer to the axle, and requiring less torque. Conversely, popping a wheelie in a longer, heavier car is more difficult unless it has a much more powerful engine. What makes wheelies very dangerous is that if the acceleration stops the car will fall very hard onto the ground and possibly explode (I have no background in automobiles, but I'm pretty sure that's how it works), or at the very least damage the car and people in it. So don't try to pop a wheelie until you're old enough to get your stunt driver's license. Until then, always drive the speed limit and wear a seat belt.
Possibly the coolest form of transportation is undoubtedly trains. They're just so darn cool. While some might write off trainsportation as a relic of the days of Manifest Destiny, it's actually becoming much more useful and cool thanks to science. The newest generation of trains does not run on short men in conductor hats shoveling coal into an engine: they run on magnetism. The trains work by strapping a very powerful magnet onto the bottom of the train and having another very powerful magnet in the tracks. The magnetic force between the two allows the train to hover above the tracks. This eliminates the friction of a traditional train and allows it to reach incredibly high speeds of up to 500 km/h (about 310 mph for those who don't believe in the metric system). The train moves because the magnets are electromagnets. This means they can be turned on and off by running a current through them. The train is propelled forward by magnetic fields in front of and behind it on the tracks that push and pull in forward respectively. These new trains are being put into use all over the world, most famously in Japan where they are known as bullet trains (because they go fast). While these trains will probably never come to America because of our crippling inability to fix or improve any of our infrastructure, they are still pretty cool and mark a significant comeback for trains everywhere, and it's all thanks to physics.
A major concern for planes in a harsh winter climate like our own is the threat of ice forming on the wings. This could potentially interfere with the lift caused by air passing over the wings and cause the plane to cease to function properly. Currently, ice is dealt with by spraying the wings with a deicing agent. This chemical lowers the melting point of the ice, causing it to melt. This process works most of the time, but it can be extremely expensive. That's why smart people have come up with a sophisticated system to cut costs. The wings would be coated in an extremely hydrophobic surface (a hydrophobic substance lacks the ability to hydrogen bond because it is non-polar and therefore does not experience an electrostatic force from the poles of the polar water molecules) causing the water to gather in little beads which would freeze in low temperatures. The wing would also have an inner layer that would detect this freezing and release antifreeze at those spots only. This would save airlines from having to deice the entire wing. Though this technology is ways away from coming to the Rochester airport, the current system works is just as effective and safe. While there might be delays and higher costs, it's worth it to know that safety is the top priority.
The only thing to do is get right back on that horse. In an episode of The Office, the character Michael Scott attempts to prove that working in an office is just as dangerous and exciting as working with heavy machinery in the warehouse by pretending to jump off the roof of the building. Michael's plan is to jump down onto a trampoline which he believes will break his fall. However, falling from a three story building (about 9m) onto a trampoline would be far from safe. Firstly, the trampoline in question was not exactly top quality. It likely had a very low spring constant given how cheaply made it was. With Michael hitting it with about 6180 Joules of kinetic energy, the trampoline would not save him from hitting the ground. If, by chance, the trampoline did have a high enough spring constant to keep Michael from hitting the ground with enough to force to injure him, the resulting force of the spring on his body would not be much more forgiving that that of the ground. Even neglecting this aspect, the energy absorbed by the trampoline doesn't go anywhere, so it would likely send Michael flying back into the air an onto someone's car. There is no safe way to jump off of a building unless it is a really small building like the kind they make for children to play house in. Luckily, Michael Scott realized that it probably wasn't the best idea and came down from the roof via the stairs, proving once again that safety never takes a holiday.
It is with great shame that I issue the following public apology. In a previous post, since deleted for the safety and well-being of this community's physics students, I committed crimes against humanity, and even worse, crimes against physics. I claimed that if one were to stick a knife into an outlet, they would not be electrocuted because the circuit could not be completed. This would be true in a vacuum, but I failed to take into account the fact that in being connected to the ground, one would indeed complete the circuit and potentially cause themselves serious harm. The connection of the individual to the ground would supply a reservoir of charge that would cause a complete circuit and electrocution. I apologize profusely to those of you who were misled by my stupidity to try sticking a knife in an outlet and I apologize as well to all of my previous science teachers, who must've thought they'd taught me better than that. It turns out that the one who thought they knew everything was not Dr. House or his writers, it was me. I promise that all further scientific claims made on this blog will be better thought out and be at least mostly true. I apologize once again, and I hope you can find it in your hearts to forgive me. Thank you very much for your time.
Because apparently all I do is watch movies all the time and I don't want to do any actual work (unless one would dare call physics work rather than fun), I am going to reprimand yet another movie for its lack of concern for physics. In the movie Iron Man 3, there is a scene in which a plane explodes or something I wasn't paying that much attention and people end up falling through the air. Eventually, they presumably reached terminal velocity considering they fell from fifty thousand feet (or an equivalent height at which airplanes fly). Luckily, Iron Man happened to be in the area, and flies around rescuing the falling passengers. There were probably a lot of things wrong with this scene, but the greatest error came at the end when the last few remaining passengers are nearing certain death at the hands of the ocean below. Iron Man thankfully manages to swoop in and rescue them inches before they hit the water. Unfortunately, if they were traveling the average terminal velocity of a human, around 56 m/s, and Iron Man slowed them down to essentially a stop in a fraction of a second, the force exerted on their bodies would likely kill them. Assuming a stop time of .4 seconds and a mass of around 65 kg, the force exerted on the passengers would be about 9.1 kN. That would be akin to having a 2046 lb weight dropped on them. They probably would've sustained some serious injuries and perhaps even died, but this would make undermine the whole idea that Iron Man is a hero and probably decrease merchandise sales. So again, we must give Hollywood a pass just this once because it's much cooler to have Tony Stark swoop in at the last moment than to have him save them all with several minutes to spare. But still, one would think that someone would at least consult a physicist or someone with an elementary knowledge of physics before making these scenes. Alas, physicists are instead confined to doing drab work such as unraveling the mysteries of the universe.
It's no secret that George Lucas doesn't give a hoot about physics, but just for the heck of it here is another issue I have with the film series. The films frequently feature intense laser fights both in outer space and on land, but what doesn't make sense is why the lasers are visible. Given that lasers would have to be highly energized beams of light to do so much damage, they should not be visible unless refracted. Those of you who remember Mr. Powlin's green laser pointer will no doubt remember that the light could not be seen until it hit the wall or was shown through chalk dust. Therefore, unless space is secretly filled with chalk dust, the lasers should be invisible. But invisible lasers would be so much less entertaining, so perhaps just this once we can overlook such crimes against science. Just this once.
If you were rich enough or your parents were lenient enough to let you have a trampoline when you were younger, you almost certainly attempted a double bounce. This occurs when two people bounce at the same time causing one to shoot much higher in the air and possibly shatter a collarbone. The double bounce is merely a case of conservation of energy. When two people jump on the elastic trampoline, their gravitational potential energy is converted into elastic potential energy in the trampoline. In order to get a good bounce, one of the participants must lift up their legs so as not to be in contact with the trampoline anymore. This will allow all the energy to be transferred to the remaining bouncer in the form of kinetic energy, which will send them much higher thus maximizing fun and injury risk.
In the attached picture, it appears that the pair of forks defy gravity. This is not possible, so how do the forks manage to balance. The secret lies in their center of mass. As you know, the center of mass of an object is the place where it balances on a pivot in all directions. In this case, the bend of the forks makes the center of mass directly on the edge of the cup. This allows the system to balance easily and give the illusion of defying gravity. This is a useful parlor trick for distracting your relatives when they ask you about your plans for the future.
After writing my last blog post, I came across the following website: https://www.tfes.org/ It is the homepage for an organization called the Flat Earth Society, which, as you might have guessed, believes the Earth is actually flat. This would seem to imply that all scientific evidence pointing to a round Earth is a product of the government and the globe manufacturing lobby. But while their idea is obviously wrong, the science behind it is not. In my previous post, I wrote about the effect a disk shape would have on Earth's gravity. These conspiracy theorists, argue that gravity as we know it is a lie. So then why do things fall? The Flat Earth Society claims that our flat planet is accelerating upward at 9.81 m/s2. If this were true, it would be similar to the classic physics problem where someone is standing on a scale in an elevator. Just as an upward accelerating elevator makes it seem like the person in the elevator weighs more, an upward accelerating Earth would simulate gravity. The FES makes a great many claims that can be supported by possible, though improbable, science. Either way, it is enough to make one wonder if in fact the Earth is flat and everything we know is a lie.
A common misconception is that Christopher Columbus discovered that the Earth was round, and that, before then, people all thought it was flat. Actually, a round Earth has been widely acknowledged and accepted in the scientific community since the days of Ancient Greece. But what if the Earth actually was flat? For starters, we would have to throw out most of the laws of physics as we know them, as a disk as massive as the Earth would collapse into a ball under its own gravity. But if somehow the large ball we live on were actually a disk, things would be slightly different. Although life near the center of the disk would be pretty normal, once one began to head out toward the edge, things would become strange. The biggest change would be that gravity, instead of pulling straight down, would pull toward the center of the disk at a greater and greater angle the farther one walked out toward the edge. This would make it seem like the Earth was actually parabolic, as the ground would become steeper and steeper relative to the direction of gravity. This would mean that, contrary to popular belief, it would be impossible to fall off the edge of the world. Once one got to the edge, they would be able to walk on it, as it would be a level surface. Then one could proceed to walk on the underside of the Earth-disk and experience an easier downhill walk back toward the center. A flat Earth would likely make everything very difficult, especially transportation. Cities would have to be built at an angle depending on their latitude in order to make seemingly level streets. In a way, a round Earth is flatter than a disk Earth, and it is certainly easier to live on.
Prior to the beginning of overtime in last weekend's Packers v. Cardinals game, referee Clete Blakeman (definitely sounds like a fake name) attempted to flip the coin. Except he didn't. The coin did not flip at all. This prompted an outburst from Packers quarterback and insurance salesman Aaron Rodgers, who demanded a reflip. Blakeman obliged and the Packers subsequently lost. But how does a professional who has likely flipped hundreds of coins in his lifetime manage to screw up like this? Excluding potential sabotage, the only explanation for the lack of a flip is physics. A coin is flipped by exerting torque on one side of the coin and creating rotational acceleration. This allows the coin to spin through the air like some sort of spinning thing going through some other kind of thing. However, if the force is applied directly at the center of the coin, there will be no torque as the distance from the axis of rotation is zero. Therefore, the coin will not flip and everyone will be upset. But there is another factor as well. The coin used was comically over-sized and, based on the NFL's wealth, made of Lil' Wayne's melted-down teeth. This gave the coin a much higher mass and radius and therefore moment of inertia. An object with a high moment of inertia is more difficult to accelerate. This allowed Blakeman to be just a little off from the center of the coin and still have the torque be negligible. Clearly, Blakeman is both a physicist and a Cardinals fan.
Today we're going to talk about the world's biggest cheetah (and for once I'm not talking about Brady). As we all know, cheetahs are the fastest land mammal and can reach speeds of up to 110 km/hr (that's 30.56 m/s for you physics purists out there) and are the only member of the genus Acinonyx. But what you probably don't know is how a cheetah is able to run so fast and change direction quickly enough to catch its prey. The secret lies in the cheetah's tail. If you watch a video of a cheetah running (instead of doing your webassign) you can see that when the cheetah changes direction, it flicks its tail like a rudder to steer itself. Like a car, if a cheetah were to attempt a tight turn at a high speed, it would tip over. This is due to the rotational inertia of the cheetah/car and the torque provided to accelerate it. The flicking of the tail provides a reactive torque that counteracts the tipping motion and helps the cheetah stay upright. In fact, the cheetah's tail is so effective that engineers in South Africa have developed a car that is able to turn sharply at high speeds with the help of a tail like structure in the rear. This design could help emergency vehicles move much faster ad potentially save lives.
One of the practice AP questions in this unit's packet gave me a little trouble when it asked what the force of gravity would be at the center of a planet. Mathematically, it would make sense that gravity is strongest at the center of the planet because gravitational force is inversely proportional to the square of the distance between the centers of mass of the two objects. But if gravity is a product of mass, then once the object reaches the center, it would be equally pulled in all directions by the two halves of the planet. Would this mean that one would be weightless at the center of the Earth? According to something called the Shell Theorem, no gravitational force is exerted on an object inside a symmetrical spherical shell regardless of the size of the shell or the objects location within it. If this is true, then that would allow a person to scoop out a large perfectly spherical section in the center of the earth and enjoy weightlessness. Of course the pressure at the center of the Earth would likely crush such a structure, but if a material that could withstand such heat and pressure could be synthesized, then one could theoretically float around deep beneath the surface. Of course any of this is incredibly impractical, but it does give scientific credence to the Dwayne "The Rock" Johnson movie, Journey to the Center of the Earth (not that such a masterpiece needed it).
The other day I was walking a dog when I saw a rather strange sight. Two men were sitting in a driveway in a beat-up old pickup waiting to turn onto the main road. On the back of this pickup truck was a massive pile of furniture. I quickly counted an armoire, four chairs, a table, and a dresser all balances precariously on top of each other. While a normal human being would have secured this unstable load in one way or another, these two men decided to take a laissez faire approach. They left the back of the pickup truck open and used a total of zero straps to fasten the pile. they were relying entirely on the static friction between the bed of the truck and the legs of the furniture. Unfortunately, as they peeles away, it became clear that they had never had the benefit of hearing Bill Nye say that "inertia is a property of matter." Perhaps the furniture wanted to stay at its old home, or perhaps it merely adhered to the laws of the physical universe, but it fell off the truck. It didn't even get out of the driveway. From what I could see, most of the furniture was still salvageable (save a missing leg or two from some of the chairs), but the lesson to be learned here is that you should have at least a basic understanding of physical properties if you want to be a mover in such a highly competitive field.
An aspect of drag force I had not considered before was momentum. When an object runs into air molecules, momentum is conserved. This would imply that resisting force is caused by the bombardment of the object by air molecules. Since momentum is directly proportional to velocity, it would stand to reason that drag force is also proportional to velocity. Additionally, it makes sense that by changing the momentum of the air molecules, a force is exerted. This force acts to slow the object down (or keep it aloft in the case of an airplane). Of course, air resistance is much more complicated than that and must look at infinitely more factors, but the idea of air resistance as conservation of momentum was interesting
Sometimes I work as a part-time gardener to make enough money to support my lavish lifestyle. The other day I was attempting to break off a dead branch that was an eyesore and also conveniently placed at a height where a passerby might bump his or her noggin on it and sue for millions. So I needed to take it down. At first I tried breaking it with sheer force. Despite my manliness and ripped biceps, I could not seem to break the sturdy limb. The branch would bend but it would not break, as I was not applying enough torque. So naturally I busted out my physics reference table to see what equations might be of help. Of course then I realized that torque would be helpful in this situation. As Mr. Tytler once told me, if you build a long enough lever, you can take the lug bolt off a tire with your little finger. So I gathered a shovel and some duct tape and made the branch almost twice as long. This time when I applied a downward force, the branch snapped and made a loud noise that scared many squirrels. Torque is directly proportional to length, so by making exerting the same force from farther away, I was able to break the branch. The important thing is that I got paid and was able to go spend lavishly that weekend.
As you know, space is a vacuum. This means there is no friction. Using this reasoning I ridiculed the characters of the low-budget 1970s Star Wars knock-off Battlestar Galactica when they claimed they could only turn off the engines to their spaceship and drift for a small amount of time. Couldn't they just accelerate to a fast speed, turn off their engines, and just coast to their destination. After all, there is no friction to slow them down. This would greatly expand their range and cut down on fuel costs. Unfortunately, it turns out I may have been wrong. Space is not as empty as we have been led to believe. In fact, there are many things in space such as hydrogen gas and space dust. These should have an extremely low drag coefficient and provide negligible friction. However, the drag equation shows that drag force is proportional to velocity, so if the ship were going at a very high speed (as intergalactic spacecraft must), it would undoubtedly encounter some friction. This explains why a ship cannot just coast indefinitely and why the actors on the television show were right and I was wrong.
In the strange discipline that is quantum physics there are many facets that are equal parts fascinating and confusing. One of these is Max Tegmark's thought experiment known as quantum suicide. In his thought experiment (which could only occur in his mind, as there is no way to test this theory in the real world), a man sits in a room with a gun. The trigger is linked to monitor the spin of a quantum particle. When the man pulls the trigger and the particle is detected to be spinning clockwise, the gun will go off and kill him. If the particle is spinning the other way, the gun will not fire and he will live. So what happens when he pulls the trigger? The gun clicks and he lives. What happens if he pulls the trigger again? He still lives. This process will continue in perpetuity, thus making the man immortal. In reality, the man is both alive and dead at the same time. This is because every time the man pulls the trigger, the universe splits in two. In one universe the man dies and in one he is still alive. The man is not aware of this split, so he does not know he is both dead and alive. This theory is known as the Many-Worlds Theory. This theory postulates that with every decision made the universe splits into two alternate realities. This allows the man to exist in a state of quantum immortality, as he is unaware that his counterparts in the parallel universes have died. This theory has gained more traction in recent years and holds very serious implications. For example, there could exist a parallel universe where the Nazis were victorious in World War II, or a universe in which I actually get my calculus homework done. The implications for both science-fiction nerds and scientists are quite far-reaching, but nature of quantum particles and their mechanics are still murky. This field has made great strides in recent years, but there is still so much that is unknown, which makes it difficult to say anything definitively. However, the Many-Worlds Theory and Tegmark's quantum suicide experiment are interesting things to think about.
While I was throwing bricks at the neighbor's cat the other day, a strange thought occurred to me: why is it that a rubber ball will bounce when it hits the ground bu these bricks do not. To answer that question I turned to my trusty frenemy physics. The reason a rubber ball bounces is because it is made out of an elastic material. This means that, like an elastic band, it can be bent and stretched but still return to its normal shape. When a ball hits the ground (or the neighbor's cat), the surface exerts a force on the ball that deforms it. The kinetic energy of the ball is transformed into elastic energy that is stored in the ball as it is deformed (this process occurs faster than the human eye can perceive). Like a spring, the ball must return to equilibrium, so the elastic energy is converted back into kinetic that translates into upward motion. Of course some energy is lost to air resistance, heat, and sound. Bricks do not have this elastic principle, and if too great a force is exerted on them, the brick will shatter. Their propensity to bounce back to you is why elastic objects are a much better choice for pelting that nefarious cat.
One of the greatest myths in popular culture is that if one were to go into outer space without a spacesuit then their blood would boil and they would explode. Neither of these things are true. While the lack of pressure would lower the boiling point of your blood and cause your bodily fluids to expand, the only ill effects would be very painful swelling. The stretchiness of your skin would prevent you from exploding (I wonder what the spring constant of human skin is). Rather than instantly exploding, you would drift about in immense pain for about 15 seconds or so until your body uses up its oxygen supply and you pass out. You could try to call for help in that small time window, but as we know space is a vacuum where there are no air molecules to vibrate and create sound waves, so no one can hear you scream. So while you won't explode from being hurled out of an airlock, it probably isn't something you want to be doing in your spare time.
One of mankind's greatest inventions is the automatic door. The idea that one once had to actually push or pull open the door to a department store now seems barbaric. But how do these marvels of modern engineering work? How does the omnipotent sliding door know that we, the humble customers, are there and require entrance to the establishment. Most automatic doors operate using a motion sensor. Motion sensors work by sending out microwaves and detecting motion using the same principle that astronomers use to determine if a galaxy is moving toward us or away from us. When door sends out microwaves, objects reflect them back to the sensor. Objects that are static send back the same wavelength as the original signal, but moving objects (like a person or stray cat) alter the wavelength through the Doppler effect. When the reflected microwaves are of a different wavelength, the door knows to open and let the customer in. This is a cool application of the Doppler effect and something to think about next time you go to Wegmans to return some stale chips.
While perusing the internet in order to further delay my impending calculus homework, I came across this picture. While I did not Google "studly old man in pool with head and forearm detached from body," I found it anyway. While the average medieval peasant might think this image the work of black magic or Photoshop, I as a student of physics recognized it as merely a demonstration of the wave properties of light. The reason his head and forearm are not attached to the rest of his body is because the light reflected off it is refracted by the water an the glass wall of the pool. The water and the glass have a higher index of refraction than standard air, so when the light comes off the man's muscular body and travels from the water to the glass to the air, it is refracted at each transition by an angle theta. Because of this angle of refraction and because the human eye cannot perceive reflected or refracted light waves, it appears as though the man's body is at a different location than his head and forearm. So the man is not some sort of mutant with a head coming out of his arm. Outside of his devilishly good looks, he is just an ordinary dude, and light played a trick on us.
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