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SgtLongcoat

While it might not be a major pastime for me, I enjoy learning about magic. Not of the satanic ritual variety, but of the slight of hand, stage/street variety. Sometimes I like to use this to harass my friends with impossible tricks, other times I just do it to practice some fine technical skills. In this case, namely how to throw playing cards.

If you have a deck, go grab it right now, and try to throw a card. Watch, as it flops to the ground like a piece of paper. Now, grab it by the corner, and try throwing it like a frisbee. Suddenly, the card will move in a straight line or arc, and, depending on what you're throwing it at, lodge itself in its target. Why does this change in motion change the outcome of the throw? To explain it simply, by spinning the card, the angular momentum of the card prevents it from being easily rotated in another direction. Combine it with the low air resistance that you create on the card's edge when throwing it in such a manner, and the air resistance prevents the card from actually fluttering down like it would if not spinning.

While I'm on the topic, let me mention that, while it could stick in the right target, a playing card CANNOT be used as a weapon. Due to its relatively low mass, it would lack the sufficient energy necessary to cause more than a small paper cut to the human body. If you don't want to believe me, however, know that this myth was tested by the MythBusters, and a card launched at 150 mph by a machine didn't have enough energy to cause more than said paper cut.

SgtLongcoat

The Phoenix Wright: Ace Attorney series is one of my personal favorite sets of logic/puzzle games of all time. Going through the cases one by one, you begin to feel like a real Sherlock Holmes... if Sherlock made wild accusations in order to buy a little time to find proper evidence which may or may not actually support them. And if Sherlock Holmes involved a bunch of quirky witnesses and pop culture references. And if Sherlock Holmes took place in a universe where California and Japan are somehow the same thing. And if... well, you get the picture. Being one of my favorite games, however, does not excuse it from defying the laws of physics.

The specific instance I refer to (being the game includes ghostly possession which transforms the channeller's body into that of the spirit and telekinetic lifting of rubble which came from absolutely nowhere) occurs during the first case of the fourth game. In this case, the victim was murdered with a glass grape juice bottle (not actually a censor for wine, as cases in later games both include alcohol and outright confirm that the grape juice is of the "non-fermented" variety), resulting in death via cerebral hemorrhaging due to blunt force trauma to the forehead. All well and dandy, right? Except that the bottle was both fully intact and fully empty. So, I got to wondering if this were actually possible, when I found the results from an old MythBusters episode where they tested something pretty similar. They wanted to know if a full or empty bottle would cause more damage to the human skull. To sum up their results, the empty bottle generated less G-force during an impact (28.1 G as opposed to 22.7 G, natural, as it weighs less), could not break a simulated human skull, and DEFINITELY broke when smashed against the simulated head.

While the in game autopsy confirms the cause of death, this creates a contradiction with real life physics. Either the bottle wasn't hit hard enough to break, and therefore shouldn't have caused blunt force trauma, or the bottle was hit hard enough to cause blunt force trauma, and therefore should have broken. While this can likely be attributed to a different makeup of the structure of the glass, I'd be more inclined to believe that this was done due to necessity, as the position of the defendant's fingerprints proves integral in the trial, which means a broken bottle would make certain things much harder to prove. In addition, as with all video games, rule of fun trumps all rules of physics.

SgtLongcoat

As many video games attest to, sometimes firing a weapon doesn't have any effect whatsoever on the shooter's momentum, even in the cold, dead vacuum of space where there's NO OUTSIDE FORCE TO CORRECT THE FORCE DUE TO IMPULSE! Impossible, no? Well, in some cases, no, it's not quite impossible.

While many might immediately think of rocket launchers, which are self propelled, and therefore would have minimal effect on the momentum of the shooter, these are not classified as recoil-less weaponry in the traditional sense of the term. Recoil-less weapons, specifically rifles, fire modified artillery shells which still behave as a simple projectile after leaving the weapon. How does this work, then? While a normal rifle would cause the gasses inside the bullet to expand in a closed chamber, propelling the bullet forwards at high speeds out of the barrel, recoil-less rifles allow for some of the gasses to escape out the rear of the rifle, compensating for most of the recoil which would normally result from launching a projectile.

This actually allows for two different side effects. First, this allows for the removal of heavy recoil mechanisms and the reduction of weight of the barrel. Second, it reduces the velocity of the launched projectile. In order to compensate for this, most recoil-less rifles launch a much heavier projectile a shorter range, in order to take advantage of the relatively light weight of the rest of the weapon.

SgtLongcoat

As anyone who's ever heard the story of William Tell can attest, shooting an object with extreme precision, especially something like an apple off of someone's head, with a bow and arrow takes a ton of skill, practice, and luck. It gets even crazier when you see somebody shoot an object the size of a dime flying through the air. Just how do stunt archers do this?

First of all, its nowhere near as easy as "train until you are 100% accurate," as arrows don't fly straight. What's that? Years of high school archery in gym proves otherwise? Well, first of all, congratulations on actually being able to aim, and second of all, you're only examining the arrow's flight path as a whole. Yes, the arrow's center of mass does behave like a simple projectile, so, for larger targets, its fine. However, as the arrow flies, the shaft of the arrow actually bends back and forth in a motion resembling a wave. This motion actually is what enables the arrow as a whole to fly in a straight line, as it otherwise would simply fall flat on the ground. As such, stunt archers need to be able to figure out where the arrowhead will be when the arrow travels to its target. This, believe it or not, can actually be brought down to a science. Simply by knowing the strength of the material that the arrow is made of, as well as the distance between the arrow and the target, archers can accurately predict if the arrowhead will actually be in the right position to hit the target. As such, most stunt archers actually use a device to measure the strength of said arrow, and will only shoot with arrows falling within a very specific range.

SgtLongcoat

In the Borderlands series, specifically Borderlands 2 and Borderlands: The Pre-Sequel, corporate villain Handsome Jack and the company of Hyperion use a device on their moon base/corporate HQ to launch supplies and killer robots down to the planet of Pandora and its moon, Elpis. But just what is said device?

During the beginning of Borderlands: The Pre-Sequel, you get the luxury of being shot out of the moonshot cannon in an emergency evacuation. Fun! But, in the chamber for the moonshot, there is no visible propulsion device: no explosive charge or rocket to launch it. So what does propel the moonshots? Simply put, the moonshot cannon acts as a railgun.

So, how does a railgun work? By connecting a projectile between two long rods, and running a current through the rods, it's possible to create an induced magnetic field which launches said projectile without the need for a conventional propulsion mechanism.

SgtLongcoat

Many have seen the Back to the Future trilogy, in which Marty McFly and Doc Brown use a modified DeLorean to travel through time. According to Doc Brown, the machine requires "1.21 Jigawatts" of power (confirmed by the directors to simply be a mispronunciation of Gigawatts) to power the flux capacitor, which enables time travel. This is achieved by bringing the DeLorean up to a speed of 88 mph, roughly 39.34 m/s. Using this information, I will do what any sane person would do: calculate the mass of the DeLorean.

Before I can calculate the mass, there are a few missing pieces I need to know or assume. First, the coefficient of friction between the tires and the road. Considering that roads at the time were mostly made of concrete, it's safe to use the coefficient of friction for rubber on concrete, which will be somewhere between 0.6 and 0.85. Being the car is in motion, and the wheels are rotating, the static coefficient of friction should be used, so I'll take the higher value of .85. Second, I'm going to assume that air resistance is negligible in this case, and that all work done on the DeLorean comes from the force of friction, which is used to accelerate the car forwards. Finally, I'm going to assume that the DeLorean moves with a constant acceleration, such that the average velocity of the car is equal to half the final velocity, or 19.17 m/s.

With that done, I can work backwards from the beginning to determine the DeLorean's mass. First of all, being power can be calculated using the equation P=F•v, and the net force on the car and velocity of the car are in the same direction, Net Force = P/v = 1.21 x 10W / 19.17 m/s = 6.31 x 107 N. Being friction is the only force acting to accelerate the car, this is also the force of friction. Now, being the force of friction = µ(Force normal) = µmg, the mass of the DeLorean = Ffriction / (µg) = 6.31 x 107 N / (0.85 x 9.81 m/s) = 7.57 x 10kg. Looking up the actual value for the mass (yes, you can find it), it's about 1230 kg, a large discrepancy. While the assumptions made above, especially concerning air resistance, don't help the numbers, the fact of the matter is that Doc Brown never fully explained how the DeLorean worked, so it's almost impossible to calculate a realistic number for its mass. Besides, would you really want him to? If so, be prepared to sit through a full movie dedicated simply to explaining the science behind it before even beginning the actual trilogy.

SgtLongcoat

In the previous post, I referenced a quote from Toy Story, said by Woody after Buzz is first introduced, in response to Buzz's stunt around Andy's room. If you haven't seen the first Toy Story (which I don't know why you wouldn't have by now) turn away now before I spoil a minor part of the end of the movie. You know who you are. Alright, here it goes...

At the end of the movie, Woody and Buzz are trying to get back to Andy, and have to chase a moving van on RC. In the process, Buzz lights a firecracker that was attached to his back, sending him and Woody into the air to eventually fly down into Andy's car. Simple, right? Well it is, until you realize that Buzz and Woody, even if you refer to what they did as gliding, shouldn't have been able to stay aloft. Disney's artistic physics license implies that Buzz's "wings" were enough to keep both him and Woody aloft, due to air resistance. While the pressure differential above and below the wings due to moving air would cause that in real life, the shape of Buzz's wings don't allow that. Because Buzz's wings are flat, the amount of air pushing up on the wings will equal the amount of air pushing down on the wings. If you don't believe this, just look at any airplane. The curvature of the wings is what allows air resistance to keep the plane aloft in the first place. In short, Buzz's flight was impossible, and would have been even more difficult while carrying Woody. 

SgtLongcoat

Let me start this by saying that the title is a bit of a misnomer. Dogs cannot fly, no matter how fast of a running start they can get. While a hyper dog may be able to leap over several people, an ottoman, and half a couch with a single bound, they have no way to force air down such that they stay aloft. In the words of Tom Hanks, "It's not flying, it's falling with style."

Having said that, dogs actually can do a ton of cool things. Namely, standing on their two rear legs. The canine body is most certainly not designed for them to put their full weight on two legs, yet they are quite clearly capable of such a feat, as many internet videos can testify to. As such, how is this possible? While their center of mass isn't usually directly above their point of contact with the ground, meaning gravity would pull them down, dogs get around this with one simple trick: jumping. Almost every video where dogs are on their hind legs has them jumping on them to stand up. What does this do? Quite simply, with the way that they jump, they cause a torque on their bodies which cancels out the effect of gravity, allowing them to stay up in such an unnatural manner.

SgtLongcoat

In the world of Pokèmon, creatures cute and fearsome are forced to fight one another by their trainers for personal amusement. But its fun, and the little buggers are left relatively unharmed (aside from Gary's Raticate, may he rest in peace), so hey, no harm no foul, right? And considering that this universe was able to spawn said creatures, it must operate on a slightly different set of rules, right? Yet one specific aspect of the universe tends to break a law that, for the most part, is held constant. That aspect is Pokèmon evolution, and the Law of Conservation of Matter.

While animals in real life are known to grow over a long period of time, Pokèmon can go from a small, 10 kg fish to a raging, 235 kg dragon in a matter of seconds, an almost 2300% increase in mass. This has to break the Law of Conservation of Matter, right? Well, as a recent Game Theory video points out, it might not. To sum up the video's theory, which uses the same example, during evolution, the 'mon absorbs matter from the surrounding environment, until it has enough materials to become said giant dragon. However, the video assumes that the 'mon absorbs specific compounds, and as such, shouldn't be possible, due to the low density of certain resources in most areas. However, the video fails to notice one specific alternative:

Einstein's Theory of Mass - Energy Equivalence.

According to Einstein's theory, mass and energy can be related with the equation: E = mc2. Assuming that Pokèmon uses this principle in evolution, they would only need to store enough energy to convert to the required mass, which also explains two things: the flash of light during evolution, and evolution via stone/location. The flash of light could be released during the process as extra energy lost in kick-starting the process, while evolution stones and locations could contain large amounts of energy which specific 'mons have catalysts for, allowing for them to evolve without the need for a long energy gain process. Heck, even trade evolution could be explained, being the 'mon is temporarily converted to energy, and the transfer could supply a large amount of energy which essentially catalyzes the evolution.

SgtLongcoat

Recently, my family and I went to the Strong National Museum of Play, amd I had to try and find a way to keep from being bored while my sisters were in the Bearnstein Bears room. Luckily, there was a huge pinball exhibit just next door, so I did what any sane person would do... and spent half an hour of my life staring at blinking lights and trying not to rage quit every time the ball fell between my flippers. Needless to say, fun times! Having said that though, there's actually alot of physics in pinball that can give you a slight edge.

First of all, how does the ball keep sliding back down to its inevitable doom? The answer: the slope of the table. Because the machine is on an incline, gravity will act on the ball such that it rolls towards the flippers.

Second, how can you read where the ball will go? While I doubt anybody has the time to measure out ball speed, moment of inertia of the flippers, etc., etc., by understanding the basics of momentum, you can get a general idea of the final direction the ball will move in. Because momentum is a vector quantity, by figuring out which way the ball is moving, and hitting the flipper so that where you want the ball to go is between the ball's velocity vector and the flipper's velocity vector, the ball should roughly go in the direction you want.

SgtLongcoat

WoP #9: Black Hole

Black holes: one of the most (theoretically) dangerous things in the universe. They consist of highly concentrated matter at a single point, such that the gravitational force exerted by the black hole is so great, even light cannot escape. However, this isn't entirely because the escape velocity is greater than the speed of light. Some astrophysicists believe that the major reason light cannot escape is because the mass of a black hole is so concentrated that it warps space around it such that every path leads towards the center of the black hole.

In addition, the high gravity of a black hole causes some time dilation. In theory, if we could get close enough to a black hole to experience the effects of time dilation, but not so close that our escape velocity would be too great to leave orbit, we could utilize a blackhole to create forward time travel. The major problem, however, would be getting back afterwards.

SgtLongcoat

WoP #8: Tightropes

So, today I saw a show in which a circus was being performed, and saw one of my favorite types of acts, the tightrope walker. Though it's one of my favorite acts, as a kid, I always wondered why they carried around the big, funny looking stick. Wouldn't having more weight make it harder to walk the rope? Actually, it's quite the contrary. The weight of the pole, extended over the distance, makes it easier to balance. Without the rope, they'd have to wiggle around like crazy on the rope in order to stay on. With the pole, by making slight changes to the angle of the pole, the torque on the pole makes major corrections to the walker's balance. As such, it creates the illusion of elegance atop the rope.

SgtLongcoat

WoP #7: Moon Drop

Let it be stated that I am a huge Legend of Zelda fan. I've played a ton of the games, and have even made it a personal goal to seek out a couple of the "older" ones. One of my two favorite games from the franchise is The Legend of Zelda: Majora's Mask, in which the player runs around the land of Termina with a 3 day time limit, trying to prevent the moon from falling and destroying the planet, and using magic to periodically reset time. This game is one of the darkest, yet most emotional in the franchise. However, it doesn't quite handle gravitational physics well.

Considering the moon in the game is constantly approaching the earth, the force of gravity should be constantly increasing, and the acceleration of the moon due to gravity should also be constantly increasing. Despite this, the moon appears to fall at a pretty constant velocity, and even seems to slow down in the game over screen, right before it hits the earth. In addition, in the actual ending, the moon's descent isn't stopped until it gets extremely close to the earth. Assuming I'm wrong and the moon is accelerating towards the earth, considering the moon's mass and the relatively great impact velocity, the force required to change its momentum from its initial momentum to 0 would be so great that there would be some form of crater on the earth's surface from where the four giant's who actually stopped the moon from falling were standing.

SgtLongcoat

One of the most beautiful, awe inspiring landscapes to explore in a video game is none other than the floating island. Imagine being surrounded by plains, forests, mountains... and blue sky and clouds as far as the eye can see. As beautiful as they are though, just how do they stay in the air?

Some games offer a semi-plausible explanation, such as giant fans on the bottom of islands, or simply "It's magic." Other games, however, offer no explanation whatsoever, and the islands simply float. The force of gravity should be pulling them down, and there isn't some giant hand holding it up, so there's no physical force pusing it up against gravity. This leaves two options:

1) A force field, likely caused by magnetism, creates an upward force on the island which counteracts gravity.

2) The island pushes something else (air) down. The impulse of the air over time causes an oppsite force on the island which counteracts gravity.

Both of these are semi plausible, until you actually factor in entering and exiting the island, which changes the island's mass, and would cause it to move due to unbalanced forces. In the end, maybe the "It's magic" definition is better.

SgtLongcoat

Something tells me that the junior/senior class trip to Italy might not be happening this year, as Italy has recently been hit by a series of earthquakes, the most recent of which hit cental Italy and was a 6.6 on the Richter scale. According to recent news, approximately 90% of buildings in the area, many of which had significant historical value, were affected or destroyed by the shockwaves, and many were injured (luckily no reported casualties). As the shockwaves radiated from the epicenter, surrounding areas felt aftershocks of around 4.4 on the scale, and aftershocks are estimated to continue for the next week or two.

Being forces between two tectonic plates at fault lines are what cause these tremors, it can be assumed that there's been an increase in the amount of tectonic activity underneath Italy. For everyone's sake, I hope these tremors end soon, because if they migrate any further south, there may even be a chance we see Mt. Vesuvius erupt again.

I wish the best of luck to the people of Italy in rebuilding and returning to their normal lives. My heart truly goes out to them.

SgtLongcoat

WoP #4: Car Crashes

A couple days ago, I was waiting to be picked up (since I'm a seventeen year old chicken who still doesn't have his license), and I unfortunately almost witnessed a car accident. A child, maybe four or five years old, went to chase after a ball which went across the street, and the driver couldn't see him because there was a parked car in the way. I tense up because I'm about ready to bolt over and help the kid, but luckily the driver stops about a yard away from hitting the kid. He's one lucky kid.

The weird thing about this, though, is that the force of friction acting on the car to move it forward before the brake is applied is the force of static friction, which is greater than the force of friction which acts to bring the car to a stop after the brake is applied, that of kinetic friction. This means that, in order for the car to come to a stop, the brake would need to be applied for a longer amount of time than the gas would to bring it up to speed, being kinetic friction has a lower acceleration than static friction.

In addition, the impulse the kid would've felt had he been hit would likely be enough to cause serious injury, considering the magnitude of the momentum of the car compared to the child's momentum in the direction of the car's motion (~0 kg m/s), and the fact that the car's velocity wouldn't change much due to the child's relatively small mass compared to the car. I truly am glad the car stopped in time, because human road kill isn't something I ever want to see.

SgtLongcoat

Terraria; one of my favorite games of all time. I've played through it more times than I can count, and have logged more hours into it than I care to admit. The game is a sandbox game full of crazy bosses and easter eggs. Needless to say, it tends to have its own spin on the laws of physics, but almost always these spins are based on real physical laws. One such way the game has fun with physics is with its reference to Valve's Portal series: the Portal Gun.

The problem isn't that the gun allows for instant teleportation (the game already has teleportation pads and potions). The problem lies in the affect of holding the gun. When holding the gun, the player's terminal velocity changes from 51 MPH (22.79 m/s) to 179 MPH (80.02 m/s). Assuming that the net force on the object is mg-bv, which should be equal to 0 at terminal velocity, meaning terminal velocity = mg/b, and g and b are constant, this means that the portal gun would be two and a half times the mass of the player. Though this would make the player insanely strong, this isn't entirely unrealistic.

However, this assumes that gravity is constant. When holding the gun, the time taken to accelerate to this new terminal velocity is the same as it would be to accelerate to the former, meaning the acceleration due to gravity is what increases 3.5x. As such, it can be safely assumed that the portal gun, as it exists in Terraria, breaks laws of physics. Though, in a video game, which is more fun? Being bound by the laws of physics, or being able to have some fun with laws that we can't change in real life?

SgtLongcoat

Undertale… where do I even begin? To describe it simply, it’s a game which shows us that there are consequences to our actions, and attempts to show that there are other solutions in video games than violence. It’s one of the most amazingly funny and heart-wrenchingly emotional experiences you can get out of a 2D game. That being said, mostly for the rule of funny, the game tends to ignore the laws of physics.

 

One of the most blatant examples of this occurs during the game’s pacifist route, where one of the characters, a skeleton named Papyrus, jumps out of a closed window, causing it to shatter. The problem? By jumping out the window, the force Papyrus exerted on the window would have been directed outside the house, meaning the shards of glass would have landed outside. Despite this, when jumping, the ENTIRE window breaks inwards, and lands INSIDE the house.

 

There are several tough bosses in this game which drive people insane, some of which also break the laws of physics… or blatantly ignore them… But the fact that one of the easiest, kindest bosses in the game can so casually break the laws of physics just goes to show how dangerous he may be…

SgtLongcoat

WoP #1: Jelly Cat

 

So, I went to RIT for a college visit not too long ago, and they played the above (slightly goofy) video about creating perpetual (never ending) motion by combining two principles derived from urban legends. The first is that a cat, dropped from any height, will always land on its feet, and the second is that a piece of toast with jelly on it will always land jelly-side down. The video goes on to state that, by spreading jelly on a cat's back, the cat will be unable to land both on its legs and jelly-side down, and will spin indefinitely. The video goes on to state that this could be used to power a train system by using the cats as a form of wheels. Unfortunately, there are several things wrong with this videos "theories."

First of all, the mass of the jelly is on a much smaller order of magnitude of that of the cat. As such, the mass of the jelly would move the cat's center of mass a noticeable amount, meaning any forces acting on the cat-jelly system should still have the same effect as those acting on an un-jellied cat. Assuming a cat will always land on its feet, this means that even a jellied cat will always land on its feet, and the jelly will not have affect that in the slightest.

Second, assuming the cat would enter a state of perpetual motion, using it to move a train would still be impossible. In order to move a train, the cat would have to apply some force to the train, and the train would therefore have to apply some force to the cat. Assuming this is the case, the cat would likely have a normal force acting on it from the train, and therefore, a force of friction. As such, considering the mass, and by extension, weight of the train (which would be part of the normal force), the force of friction (which opposes motion) would likely be of a much greater magnitude than any other forces acting on the cat, and, therefore, the cat would be decelerated until it eventually reached a stop. Therefore, it would be impossible to use a cat to power a train system.

Finally, the weight of the train would crush the cat. Why doesn't anyone want cats to live?

SgtLongcoat

Introduction

Hello, and welcome to the World of Physics. Considering this is my first post, I feel it necessary to describe myself a little. First and foremost, I'm a huge fan of gaming, so a majority of my posts will likely discuss their insane simulations of physics. In addition, I'm a Boy Scout, currently working towards my eagle rank. I'm great with technology, and took several classes in programming over the course of my high school career. In the future, I hope to study programming further, as well as game design, and I would ideally like to break my way into the video game industry. For a slightly more realistic career choice, I simply want to be a computer programmer. This is part of the reason I'm taking Physics C this year. Especially in the case of game design, understanding physics allows for the creation of much more realistic animations and events. On the other hand, I also really like learning how a lot of stuff works. This year, I hope to learn much more about physics on the quantum level, as I find the lack of decisive data on the field interesting. Aside from that, I have no idea what to expect from this class, so I guess I'm excited simply to see what it holds. Well, that's the end of that. If you managed to sit through that entire wall of text, you have my utmost respect. Take care, and you'll be hearing from me again soon.

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