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## Speakers and Their Circuits

Not that long ago I came up with a fun project idea when I was bored. I had some spare speakers laying around and felt like a fun thing to do would to add them to my current speaker system to help fill the room with sound better. To do this I drilled small holes in the back of my current computer speakers and then connected some wire in parallel, I then ran this wire through the ceiling and then soldered the leads to the speakers. By connecting them in parallel I reduced the resistance of the circuit but I also increased the current, thanks Ohms law! I thought this was all good, but then my dad brought up a good point, would the increase in current cause the amp in the speakers to blow. To my luck it seems like it all worked out fine as a few weeks later the speakers are working just as they were before. Another bit of physics that helped me in this project is magnetism. At the back of all speakers there is a sizable magnet used to vibrate the membrane and create the frequency of the music.  I used this magnet as a form of mounting, I have ceiling tiles in this room so I just stuck the speakers to the ceiling where the metal was in the ceiling and I was done!

## Football to the Face

On a youtube channel that you may have all seen at one time or another they have made a video about throwing a soccer or football at somebody's face. This channel, called The Slow Mo Guys, records things in slow motion. In this video they show a face getting hit by a soccer ball in supper slow motion. The cool thing about this is that you can see the inertia that the head holds and its resistance to movement from the soccer ball. The other cool thing that you can see in super slow motion is that the energy the ball has goes from kinetic energy, as its moving, into potential energy, as the air inside is compressed as the ball is mushed against the head.

## Flopotron

A mad scientist over on youtube has made a monstrosity of an instrument, it is made of 2 scanners, 8 hard drives, and 64 floppy drives.... 64... The reason for all of these strange electronic parts is so that the creator can play many different songs. Now how do you get these parts to sing the sweet sound of music. Well first off what is music, it is a bunch of frequencies all put together to create harmonies that sounds good to the ear. This is exactly what the flopotron is doing, each drive bay is set to a specific frequency and the program that he writes detects the frequency in the song and sends a command to the appropriate floppy drive to spin at that frequency. This is why there are so many floppy drives, so that songs can be faithfully recreated. While we covered what the floppy bays do, we have not covered the scanners or the hard drives, well the scanners operate on the same idea, except that they are mapped to the lower tones of the song as a scanner normally operates at a lower frequency than a floppy drive. The hard drives very simply act as the drums in the song, now as to how the creator managed to single out the drums in a song I don't know. My best idea is that if the program detects a a very sharp spike in amplitude then it will trigger a hard drive.

## NFC

In most modern smartphones there is a feature called NFC, which is short for Near Field Communication. This tech uses electromagnetic induction with two loop antennas and the information is transferred on a radio signal in the 13.56 MHz band. If a device approaches another device this is called peer-to-peer sharing and both of the devices generate RF fields to transfer data. But in the case of a NFC tag, the tag does not have its own power supply, therefore it uses inductance from the active device and then transfers a RF signal. There are many applications for this technology that anybody with a phone can do. Currently anybody with a relatively new  iPhone or Android can use NFC to wirelessly pay were it is available. But if you have an Android and some NFC tags around you can program them to carry out simple or complex functions. The tag pictured above, only about 3.5 cm2, has been programmed to give the wi-fi password to anybody that touches their phone to it.  Down below you can see the inside of the tag thanks to it being thin.

## PolyMagnets

In the E&M course we learned that there can never be a mono pole of a magnet. We can tell this because of Gauss's law for B-field. But a company has found a way to print different poles on the same surface, they do this by printing what they call "maxels" onto the surface of a magnet. The different applications for these could be magnets that attract to a certain distance and then repel once closer together. They can also make "short-throw" magnets that are extremely strong but only attract a few centimeters from the surface of the magnet. It is hard to explain everything that these magnets and their designs can do so there is a video below about how they are made and what they do.

## Fly System

The High School recently put on a musical production called The Addams Family, for stage crew we had to build the set which includes something called a fly system. On this production we had many parts of the set on the system in order to fly them in and out. For instance one of the bars held an entire wall that was used as a backdrop that would only let in small spots of light to resemble stars. This was moved often as the scene changed from inside to outside a lot. The way that the fly system works is a set of counter weights that offsets the weight of whatever is on the bar. As you can see above the weights are put on a platform that is connected to a long rope on a pulley system, however this pulley system is 1:1 so there is no mechanical advantage. Each weight weighs about 20 pounds, so on the large stack in the picture it is meant to lift something weighing around 320 pounds. The problem with trying to move something so heavy is that the bar is not going to want to move due to inertia as the mass of the system is double the mass of the object being lifted. Another problem that arises is that if we need to make a quick scene change then the fly needs to go up quickly. The big mass and the large speed give the system a lot of momentum that needs to be stopped carefully or else something may break.

## Boston Dynamics: Sand Flea

Another crazy creation from Boston Dynamics is the Sand Flea. This little robot has the ability to jump, very high. the 11 pound, or 4.99 kg robot has the ability to jump 30 feet in the air, or 9.14 meters. Using potential energy we can calculate the energy needed to launch the robot. Using mgh we can see that the robot outputs 446.96 Joules of energy for a full height launch. Also assuming that no energy is lost the launch velocity of the bot is about 13 m/s. Boston Dynamics say that the robot can launch about 25 times, giving the total energy within the robot to be about 11174 Joules or about 69837500000000000000000 eV.

## Boston Dynamics: Handle

Quite recently Boston Dynamics made another cool looking robot that is built with two legs and runs on wheels. In order for this robot to be able to move around without falling over. The ability to not fall over is helped by inertia and the very complex computers within the robot allowing for many calculations to be made in order to put the robots weight in exactly the right spot. What is the most surprising thing about this robot is it's ability to jump completely autonomously. It is able to detect an object in front of it and make the correct calculations to jump the object and safely land on the other side. The way the robot turns and stops also shows how inertia is used, as the robot is stopping it will lean back as to counter act the inertia wanting to send the top of the robot forward. Again as the robot is turning to either side, it leans the direction it wants to go in order to not tip over. Here is a short video demonstrating all of its sensibilities.

## Pendulums

As we know through kinematics the period of a pendulum is determined by its length, by increasing the length of the pendulum the time it takes for one cycle gets a little longer. If we line up a bunch of pendulums in a row and just make each string a little longer than the last we can make a very cool looking pendulum wave. Eventually these pendulums will become out of sync and it will look like a mess, but they will follow a pattern and will eventually make the very satisfying wave form once again.

## Atlatl

In old times, hunters didn't have guns and cool stuff to help get food. They had to come up with a new and genius way to hunt animals for delicious food. Around 21,000 years ago, some people in the modern day french area came up with the idea of using a lever arm to be able to throw a spear faster, farther, and more accurate. The way in which this device works is that it acts on a lever arm. Since the throwing arm is long more force is applied to the object, effectively multiplying the force put into the spear.

## Kerbal Space Program

A fantastic game that has an incredible physics physics engine is Kerbal Space Program. At the end of Physics C we do get to play with this game, but I own the game and have had many fun times in it. The premise of the game is you own a space agency on the planet Kerbin (earth). You have to design rockets or planes that can power themselves taking into account of lift and mass of the aircraft. You also have to worry about how the atmosphere will effect the craft including the drag due to air resistance. The game also lets you do gravity assists around any planet, probably using the gravitational force formula. It is a fun game to just mess around in and see how many rockets you can strap to a single capsule. But it can also be very difficult because of the real world physics you have to deal with when trying to land a space craft on the Mun.

## Brachistochrone

A recent Youtube video from a channel called Vsauce caught my attention. In the video he mentions this line created by a specific set of geometric events. This line is quite special in its properties, if made into a 3D object it is the fastest path from one point to another. This is due to the perfect balance between distance traveled and velocity. In this video you can see the three different paths that are built, the linear path, the Brachistochrone path, and the 'extreme' path as they call it. The linear path has the least amount of distance traveled, but also at a slower rate then the others. The 'extreme' path has the greatest speed, but also the most distance to travel. And the Brachistochrone path has the perfect mix of speed and distance to travel making it the fastest. Another interesting property of the Brachistochrone curve is that no matter where the ball starts on the path it takes the exact same time to reach the bottom. Here is the link to the full video if you are interested in the geometry part of it too.

## The Grand Tour

In this weeks episode (Episode 11) of The Grand Tour, a motoring show with the old presenters from Top Gear UK, there was a section in the show were physics played quite a big role in getting a shot right. In the shot they fired a car, assumed off of an air cannon, onto a boat. In order to do this somebody needed to calculate using kinematics how far the car would go given a supplied force. Taking what was shown in the show it is quite difficult to try and guess exactly how they did given there is too many unknown values. I can imagine that they also took some air resistance into the calculation as they landed the car almost directly on the boat. Lets try to find how far the boat is from where the car is launched. In the video the car seems to be launched from a fairly low angle, lets say 25°. I can also tell from the video that the time the car enters the frame to the time it comes in contact with the boat is close to 2.5 seconds, taking into account they didn't slow the footage down. With this time we can use the equation to find it's initial velocity using Vf=Voy+a(t/2). With this calculation we find that Vyo is 12.25 m/s. Using some trig we can find Vx=(12.25/tan(25)) which leaves us with a Vx of 26.27 m/s. Then using ΔX=Vot we can find that the distance the car has to travel is around 66.88m.

## Waffles are the best

Awhile ago in class, our table group got in quite a heated discussion on which breakfast food is the best. Now the other side, pancakes, tried their best to convince me of the qualities that make them better than waffles. They brought up point such as fluffiness, and taste, but they failed to ignore that waffles can also have both of these properties. The way to achieve these properties is the cooking time and the temperature. In order to get maximum fluffiness, cooking for a lesser amount of time does not let the batter cook quite as much. Some points that I would like to bring to the table that make waffles way better is the increase in surface area that increases the flavor. Another feature that makes waffles much better is the pockets that holds the butter and the syrup. Lastly waffles are much better because they are much faster to make as both sides get cooked at the same time.

## Prince Rupert

There's a YouTube channel that I watch called SmarterEveryDay, in one of his more recent videos he used a slow motion camera to see how a bullet would effect a Prince Rupert drop. Before I talk about the video I will first explain what a PR drop is. How they are made is some molten glass is dropped into some cold water, creating an incredibly strong price of glass. However everything has a weakness, in this case it is the tail of the glass piece which is incredibly fragile. The hardness of the glass comes from the rapid cooling creating a bulb that has a cold exterior that pulls inward on the hot interior which pushes out. These forces equal to something that is bullet proof. And here is another video of his showing the properties of the PR drop.

## SR-71

The SR-71 was developed in the 1960's by Boeing. This was a revolutionary aircraft in that it could travel at Mach 3 speeds, or 3 times the speed of sound. This plane is quite strange because when it is sitting on the ground the plates of the aircraft don't meet up properly and the plane actually leaks fuel. The reason behind this design is since the plane flies so fast and so high up. At an altitude 80,000 ft the pressure on the metal on the outside of the aircraft is so little that the outside begins to expand, the engineers at Boeing had to account for this so they made the panels fit together loosely. Another factor for why the metal would expand in flight is that it would get very hot flying at mach 3 speeds. At such high speed the external body would reach upwards of 500 degrees, and the inside of the windshield would reach temperatures of 250 degrees, this is all caused with how much friction the air has on the plane causing this massive amount of heat. To deal with this massive amount of heat they had to develop a special cooling system that would take the hot air from inside the cockpit and put it in the fuel right before being used.

## Autonomous Landing

Anybody even slightly interested in science and technology will have heard of a relatively new space company called Space-X. They are very close to launching yet another craft into space set currently for Jan 14th. But, one of their most memorable accomplishments, for me at least, is when they had a Falcon 9 rocket land on an autonomous barge that was floating in the Atlantic Ocean. The physics and calculations that had to be done before hand, and during, had to be crazy. The team at Space-X would have had to write programs for the rocket and the ship to be able to talk to each other, they had to have very precise GPS to put the rocket in the same place as the ship. Other things they had to account for is that the ocean is wavy and the barge would be moving all over the place, they had to make the barge be very stable and still, making it move to directly under the rocket. To make sure that the rocket didn't have too much speed as it touched down on the barge they had to program for a very precise 'suicide burn' that would stop any lateral movement and greatly reduce the vertical movement. All of these physics calculations came into a very amazing and groundbreaking landing. Hopefully Space-X will continue to do new and exciting things to make space travel cheaper and safer.

## Surface Tension of Water

In this picture above it can be seen that the gecko is standing on the water, but how? Well, in between the water molecules in this tank there are hydrogen bonds that connect the molecules together. What is surprising is that the gecko is able to stand and walk on the waters surface and not just stand on the surface. You can see that the water is 'bending' under the weight of the gecko and that the bonds in between the molecules have enough force to not break and let the gecko fall through. The way the gecko is able to stand on the water is to maximize its surface area as to not put all of its downward force onto one spot on the water. This works on the same principle that a snow shoe works. The larger the surface area, the more weight can be held by the water. This also works if a leaf is thrown onto some water, the leaf does not float but rather does not even break the surface of the water.

## Ice & Land Sailing

As you know I have written many a blog posts about sailing. Now when it turns cold in the winter, normal sailing has to stop because of the ice. But some persistent people can't let sailing go over the winter. They take to the ice. What is so surprising about ice sailing is that the 'boats' go much faster than they do in water. And I mean a lot faster. The main explanation as to why the boats go faster is because of the drastic reduction in friction that occurs. The boats that are made to sail on the ice only come in contact with the ice on relatively small ice skates. Now compared to the friction that happens with a normal boat pushing through the water, these boats can reach some pretty significant speeds.   When it's not as cold and there is no access to water, people take to the desert for land sailing. People have reached speeds 126 mph, and the name of the game is efficiency and reducing friction.

## The Serenity of Snow

If you live anywhere remotely cold, you have experienced one thing snow. With snow comes many things, terrible driving, ice, shoveling driveways, all not fun things. But if you have ever taken a walk through the woods on a snowy day, you will recognize one thing, or rather a lack of one thing, sound. The reason why it becomes so quiet when there is snow on the ground is due to the physical shape of a snow flake. Because there are so many snowflakes on the ground, there is a lot of empty space between them. This large amount of space causes the snow on the ground to be a very good sound insulator. To test this out next time there is snow on the ground, grab a friend, go outside and stick your head under the snow and yell. Your friend can then observe how muffled your sound becomes.

## Maglev Trains

In my previous blog post I talked about how the Hyper Loop worked, the maglev train works in a very similar manner just in a less efficient way. As seen above the train actually wraps around the track and 'floats' on the track by using magnets to pull the train up into the air to reduce any friction of the track. There is also a 'guidance' magnet to make sure that the train stays centered on the track and that it won't crash into the sides. As mentioned in my Hyper Loop blog air resistance can be a huge factor as to how fast these trains can go. Because these trains are not in a sealed tube they have to deal with the problem of air resistance, this is solved by giving the train a very pointy front as to cut through the air more efficiently. (Personally I think they look a little like a platypus)

## Hyperloop

Some of you may know about the new development from the amazing person that is Elon Musk, the hyper loop, The new radical form of transportation could make trips from NYC to LA take under 4 hours. The ways this is possible is how the system will be operated in tubes that air will be sucked out of drastically reducing the air pressure and therefore reducing the air resistance the pod has to counteract. Another technology that the system will use is magnetic levitation, which is currently used in high-speed trains. When the pod floats in the air it will reduce the drag on the ground because it will not be touching anything. This dirastic reduction of friction from the air and from the ground allows this pod to go close to 800 mph will very little energy lost to friction. Predictions on when this new form of transportation will be ready is around 2018, here's hoping.

## The Deathroll

In small boat sailing there is a type of capsize called the deathroll, and from the name you can probably tell that it is not the most fun thing to do. Let me start off with a picture of this looks and it will help with the of how this happens. Here we can see that is quite windy and that the boat is also on its side, not good. This can happen when one sails in a direction called "by the lee", this is when the flow of wind on the sail becomes reversed from the normal direction. On the right, called downwind, the wind is following across the sail from left to right, or from the mast (the big dot) to the end of the sail (the leech). This is how normal sail flow works, but when we go to "by the lee" the direction of the wind across the sail changes from leech to luff (end of the sail to the mast) as shown by the green arrow. When this type of flow exists on the sail the direction of the force of the sail also changes direction. On the left of the diagram the boat will tend towards leaning to the right, this is the same direction the force of the sail is in. On the right of the diagram the force of the sail is towards the left causing the boat to want to capsize like the first picture.   This can be explained by this diagram. Now imagine the direction of the arrows reversed.  (My terrible paint rendition)
The big arrow represents the force of the sail and we can see that it is pointed to the side of the boat that the sail is not on, this leads to our dreaded deathroll.

## The Physics of Hiking

In dinghy sailing a persons weight becomes a much bigger deal in sailing the boat and keeping it upright. As it gets windier out on the water more force is applied to the sail, and the boat is tipped, or heeled, over more. This is were the weight of the sailor becomes more important. In order to counteract the tipping force of the sail, the sailor needs to move their weight out of the boat to create a stable system.   In the picture above we can see that the sailor has to "hike" out of the boat to counteract the force of the sail pushing the boat towards a capsize. Since the wind is always changing the sailor needs to constantly be moving around and shifting their weight in and out of the boat. This is very similar to how torque work in that the farther a mass is out of the center the more force it applies in the direction of gravity. If the system of the boat is not in equilibrium, caused by lack of hiking or a strong gust of wind, the boat can end up on it's side, this is called a capsize.

## Physics of a Sail

Most people think that a sail works only in one direction, thanks in part to the tall ships of the past.  (these things) What appears to be happening here is the wind is just pushing the sails and then in turn pushing the boat forward. But what actually is happening here is a vacuum. As the wind fills in the sail it creates a high pressure system on the inside, the lack of wind on the front side of the sail creates a low pressure zone, and since systems move towards a lower pressure the boat gets pulled forward. This also applies to modern boats and this lets boats go into the wind . You can see that the resultant force pulls the boat forwards, and so the boat would naturally get pulled sideways. This is solved with a board that is put directly beneath the boat so the sideways force it directed forward.