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jrwalther
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Blog Entries posted by jrwalther
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Push ups are probably the most common form of a workout you will see. They are easy and can be done almost everywhere, but how good of a workout are they actually giving people? There are different ways to do a push up but when done correctly, most people will be lifting around 65% of their body weight. This would be when someone is doing the standard position of having their feet kicked out. When a push up is performed on the knees instead of feet extended, we see that the amount of body weight they are lifting goes down by around 15%. These percentages show how push ups can also be conformed around what each person wants. Some can be putting in more of a workout while others can adjust their position in order to suit their needs or put in more reps.
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This week I focused on chapter 5 in Mechanics. This included momentum and impulse, conservation of linear momentum and center of mass.
Areas that went well for me were momentum and impulse and conservation of linear momentum. What helped me to really understand these two topics were first understand the graphs that went along with them. This included Force vs. Time graphs showing the impulse to be the area under it. These graphs gave me a better understanding of what I was solving for when I got to problems.
Center of mass was the topic I had the most difficulty with. However plotting the points on a graph helped me with this as well. The equation Xcm= (m1x1+m2x2).../m1+m2... really helped me understand finding the center of mass of different points. Finding it for other objects such as rods however was still quite challenging.
My major key to success this week was working more with graphs. Once I understood graphs whether it be just plotting point or graphs such as Force vs. Time, they all helped me get a better understanding of the topic I was working on.
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Throughout my life I have heard many rumors of asteroids hitting earth or the moon but I've always wondered what kind of damage an asteroid could really cause. The size of the explosion would be most impacted by the kinetic energy of the object that caused it. This would mean that the mass and the velocity of the asteroid would be the main factors in the damage. The average speed for asteroids approach either the earth or the moon is around 17km/hr. Now that we have the speed, how can we find the mass of an asteroid traveling that fast through outer space? Mass is calculated through the density and diameter of the asteroid. The typical diameter for these objects are around a few hundred miles and the densities range for 3-8g/cm^3. We can then find the kinetic energy and the angle at which the asteroid will strike the surface to determine how much damage any given asteroid will cause.
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Popcorn has lots of physics behind the little pop. Until recently, popcorn had only been studied for it's chemical properties and never the physics behind why it pops the way it does. It comes from the fact that their is water in the kernel. When it is heated above 100 degrees Celsius, the water turns to steam and expands inside the kernel. It continues to expand until the shell can no longer support the pressure and it eventually pops. As soon as it pops, the starch cools it down and ultimately turns it into the white flake of popcorn.
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The physics behind clouds can actually be a whole profession. It turns out clouds are much more complicated then most people may think. At the base of it, clouds are made up of microscopic water droplets and or tiny crystals of ice. These droplets are initially formed from condensation onto the nuclei then the air is supersaturated. This happens when the air exceeds a critical value of condensation known as the Kohler Theory. These condensation nuclei are a big part and are necessary for cloud droplets to form. In warm clouds, larger cloud droplets fall at a higher terminal velocity; because at a given velocity, the drag force per unit of droplet weight on smaller droplets is larger than on large droplets.
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This week I studied chapter 4 which included work, energy and conservative forces, conservation of energy, and power. I found however that I spent the most time learning and working on conservation of energy.
Areas that went well for me included work and power. Work was mainly review and it was good to go back and solidify my knowledge on the topic. This was the same for power as I found I didn’t take many notes. Most of it was review and the questions seemed fairly straight forward.
The topics that were more challenging was energy and conservative forces and conservation of energy. What I struggled with at first was the ability to start a question. I was struggling to understand how the energy of a system was being affected and putting it into an equation. However, once I practiced that more and more and was able to do it, the rest of the question came very easy. I would then just substitute in the formulas and would continue with the question.
My keys to success are very similar to last weeks as I followed my own keys to success and found they worked very well. I paused a lot more during videos to make sure I was keeping up and understanding every that was happening. I also answered the examples on my own first and then would either compare my answer or get help if I was stuck.
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I watched a cool lab video on a professor giving a visual representation of gravity. The idea of gravity has always been pretty easy for me to understand and easy to use in equations but where I begin to lose that understanding is when we leave earth and look at how it holds everything together. How space is constantly expanding but these planets, moons and stars are constantly effecting each other. In this video you get to see how gravity really makes these things work together to make space what it is. The part I found coolest was when he explained and showed why all the planets are going around the sun the same way. In this case it is clockwise and anything going the opposite way around the sun was or would be eliminated. This was due to collisions and as he says, those going counter clock wise were not heading in the 'preferable direction'.
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When put into its simplest terms, guns are not very complex machines. The goal is to deliver the maximum destructive energy with the minimum amount of energy to go to the shooter. Better more expensive guns will do a better job at accomplishing this task. However, conservation of momentum is true in guns as well. That means that the momentum delivered to the target still has to be equal to the momentum felt by the shooter. This is felt through the recoil of the gun. That is why bigger more powerful guns will have a bigger kickback on the person shooting it. The goal of a firearm is also to use energy efficiently and that is dependent on its construction. The two main factors to this energy efficiency are the caliber of the gun and it's barrel length.
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There is surprising a lot of physics that goes into a simple motorized bike. Even something simple on it like the weight of the tires. They are very important and in many cases can be the difference between you flying or stalling. This is because of leverage on the bike and the wheel is basically just a round lever. That means that the bigger the wheel and the more weight, than much more power is needed to move that wheel. This could be needing a bigger motor as a whole or may just slow the bike down. Another factor is the friction that goes into these bikes. Friction drive can have both advantages and disadvantages such as ease of installation. However it may not be able to be used in rain or wet conditions and the tires may wear done much faster. That is where the designers of all these bikes have to decide the ratios they want or friction between all these factors that come into play.
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Catapults are ancient weapons known for doing lots of damage from a far distance. But how can a simple machine launch such big objects so far? It comes down to the way the machine is built in which it creates large amounts of potential energy by either twisting a rope or flexing wood. This potential energy is then transferred to the object when it is released. One of the most common catapults is the ballista which is basically a giant crossbow. In this the potential energy is stored in both the tension in the rope and the bent arms on the bow. The tension in it acts as a spring so in can be calculated using U=1/2kx^2. This is then converted into kinetic energy when the bow is released and that is where it is able to fire heavy objects very far.
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Mafia 3 is a new open world game on the market and is featuring some pretty cool physics. One of the main focuses for the developers was the driving. It is crazy to see how far video games have come and Mafia 3's driving is a great example of that. The game takes crashes into account when the player is controlling the car. Crashes now have a big affect on the handling of cars. The game also offers two modes of driving, arcade and simulation. Arcade is similar to most video games in which driving is very easy and unrealistic. Simulation however is basically a driving simulation in which players will struggle to keep control over their car. On top of all of this their are four camera options when driving to make it look much better from which ever angle you choose.
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A golf balls dimples are often overlooked as just being a design that someone decided looked good when in fact they play a major role in the flight of the golf ball. Ultimately, the dimples increase the drag of the ball slightly. But another big effect is that they increase "Magnus Lift" which is a lifting force experienced by rotating objects travelling through a certain medium. This lift is present because the ball often has backspin when it is driven with a club. Golf balls flights are very different from most objects as they don't follow an inverted parabolic flight. Their flight can be seen in the diagram below.
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Paper airplanes are something almost everyone has made but most people don't really think about ways to make it better and why some are better than others. The main factor in creating a successful paper airplane is making sure it is as aerodynamic as possible. Limiting the amount of factors to create resistance will result in a more successful trip. This includes making a tail that air will glide right over instead of getting trapped on. The two forces acting against the plane in flight are drag and gravity. Drag has to do with the aerodynamics of the plane as eliminating the factors to trap wind will help it and the way to fight gravity hurting your plane is to make it as light as possible. The two forces helping the plane in flight are thrust and lift. Thrust is the forward movement of the plane. The initial thrust comes from the thrower and after that, it really just becomes a glider. Lift is the air below the plane pushing up harder than the air is pushing down from above. That is why the wings of planes are curved so that air moves more quickly over the top of the wing creating a upward push.
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A lot more work goes into creating a more smart life-like video game each year including Fifa. A major break through in Fifa 14 was that they finally figured out how to make the ball sail smartly through the air. The engineers working on the physics of the game finally found the problem that was making the ball look like it was just shot in a linear path. They found that their drag coefficient was broken. This models air resistance and affects the trajectory and speed of the ball when it is in flight. In previous years the ball was violating the laws of physics by accelerating and decelerating at rates unaffected by the initial kick speed. This fix also fixed the spin of the ball in flight. Previously the ball would be spinning one way but would curve the other way. With this new air resistance fix to the game, the ball now has realistic trajectory when it is kicked, a more realistic acceleration and deceleration, and a more realistic spin on the ball when it is in flight.
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This week I focused on the first three chapters of Mechanics, the introduction, kinematics and dynamics. I focused more on dynamics as I feel that is the area I needed more work on but both were very helpful.
Areas that went well included most of the projectile motion. Describing motion 1 and 2 were also just review as I knew almost everything covered. Circular and relative motion was a little harder but it made more sense the more I sat down with it and compared it to translational motion. It is very similar in how you calculate and derive expressions as well as equations you use such as converting kinematic equations by just replacing certain variables with their angular equivalents.
There were a couple of areas that I found to be more challenging. One being Tension as it was always an area that I struggled with. As I went through however I began to pick up tips on this as well that would help me. One being to establish a positive direction right away. The next being to draw free body diagrams of all of the forces affecting the Tension of an object. After I got these things down it seemed to come a little easier. Calculating friction was also something that I found to be challenging.
My keys to success would include slowing down when I am watching the educator videos. It helped me to slow down and pause here and there in order to catch up and make sure I understand everything that has been said to far. I used this the most during derivations as it helped me understand each step of it.
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- 707 views
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Waves have a surprising amount of physics behind them, and not the waves at football games. The simplest definition of wave motion is that it moves energy from one point to another. Waves are an oscillation of energy that travels through a medium. Their are tow main types of waves, one being mechanical waves. Mechanical waves travel through a medium and are then restored by restoring forces to reverse the work done. The other type of waves is electromagnetic waves in which the main difference is that they do not require a medium. They consist of periodic oscillations of electrical and magnetic fields generated by charged particles,
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People who are new to soccer almost always begin kicking the ball with their toe. It seems like the best way to shoot because of how much power you are able to gain. What people don't realize is the control and accuracy that is lost when this happens. The best way to hit a ball for both power and accuracy is with the inside of your foot because of the major increase in surface area you are hitting the ball with. Kicking a ball with your toe makes it much more open to have spin that may be unwanted. Striking the ball anywhere but the center will cause either top spin, side spin or back spin and you often have little control. When you use more surface area with the inside of your foot you are able to get these same motions but with much more control as it becomes less likely of a miss hit.
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I am a black belt and I always enjoyed the physics behind karate as they are often more complicated than most people first think. When two people line up to fight, they both bring a certain amount of kinetic energy to the fight. This is determined by their weight, height, muscle strength and also their physical health. The main principle behind karate is to use your body to channel this energy and make maximum use of it. It also focuses on how you can take away from your opponents with smart blocking a defense maneuvers. We can often base the power of these punches on F=ma^2. Since our mass is going to be constant it is important to find ways to increase our acceleration of the punch to generate more force. When you combine this with the ability to channel and make most of your kinetic energy, you give yourself a huge advantage in any fighting situation.
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Marcus has been wondering why I always win in our 1 v 1 basketball games and their is lots of physics behind it. The first part of my success is how high I am able to jump. There are horizontal and vertical components to jumps and being able to shoot and or block shots during the top part of the flight plays a major role in winning. I also am able to jump higher giving me the ability to have a longer hang time. This increases the time during the top part of my flight. The equation to calculate my time during the top period of the flight is d = V1t — 0.5g(t)2
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Video games are becoming more and more physics based in order to create a more realistic gaming experience. Battlefield 1 is one of the biggest first person shooter video games out right now and they did not forget about the physics. In call of duty sniping is very different from battlefield. In call of duty their is no bullet drop so if you aim at someone and shoot you kill them. That is not always the case in battlefield. They take into account bullet drop and drag. That means when using a sniper from long range you often have to aim above the person you are shooting at in order to account for this bullet drop. It ultimately creates a much more realistic experience for the sniping element to the game. It will also do this with heavy guns such as tanks and anti-aircraft weapons.
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Humans are clearly not as well suited for the water as we are for land, just look at a human body. We can't hold our breath for very long, and we get very tired very quickly in water. The main reason for this is the difference between the water and the air. The biggest difference between the two is that water is much more dense. When a human walks on land, the main thing your body has to do is work against gravity and then friction between our feet and the floor. Air resistance also becomes a bigger factor as wind increases or we pick up speed. The main force opposing a human in water is drag or water resistance. This can be controlled though by the way we move through the water. The same way a cyclist tries to minimize surface area being presented to the wind, a swimmer wants to minimize the resistance to water they may be facing. This is why many of the different ways of swimming are so efficient. The different strokes used in competitive swimming and just to swim fast, are ways humans have found to effectively cut down on water resistance and drag.
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The purpose of a wind turbine is to turn the kinetic energy of the wind into electrical energy. This is the idea of most machines as energy can only be converted, it cannot be created or destroyed. Like any moving mass, the kinetic energy is calculated through the equation K=1/2mv^2. For calculating the kinetic energy in a wind turbine we would use the wind speed for velocity. The mass would be the particular volume of air. You can also find the power in the wind a turbine is using to generate its electrical energy. To find the power you would use the equation P=1/2 x air density x area x wind speed^3 x time.This shows us that the power of wind is dependent on 3 variables. We see that the area affects the power showing us that location of these wind turbines will actually play a role in how much power is generated while the others cannot be controlled.
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I think that everyone knows how a hot air balloon works in theory but what are the basic physics behind it? The basic concept of it is that it blows hot air into the large balloon at the top to create buoyancy which eventually causes the balloon to lift. The air inside of the balloon is ultimately less dense than the air outside and this difference in density is also what causes the balloon to lift. The principle behind this lift is called Archimedes principle. This states that the upward buoyant force exerted on a body is equal to the weight of the fluid that the body displaces and acts in the upward direction. This is the same principle that describes how boats stay afloat in the water.
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The brain goes through lots of weird stages and experiences while sleeping that are very different from when you are awake. For one, the brain waves slow down dramatically. When awake the brains frequency is around 30hz and that drops to less than 3.5hz when the person falls asleep. There are around 5 stages of sleep every time you go to bed at night. The first stage includes a very light sleep while the second becomes slightly deeper. The third and fourth stages are the deepest part of it and the fifth stage is where dreaming occurs and their is an increase in heart rate and eye movements. Gravity also plays a role during sleep and is the force that pulls you to the bed and is the reason that sleep would be much different in zero gravity. It would be much more comfortable as you would never have overlapping body parts and may be a way to a better nights sleep!
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The are two main factors that affect a Frisbee during flight. Gravity accelerates the object downward at 9.8 m/s. In the air, lift and angular momentum act on it. Lift is created because of its shaped surfaces while it travels through the air. The reason a Frisbee flows so clean and far through the air is because the air flowing over the top of a Frisbee is much faster than the air flowing beneath it. The Bernoulli Principle also describes why is maintains this flight. It says how their is lower air pressure on top of the Frisbee than beneath it causing it to rise. This principle is also the reason that planes take off, fly and land. So ultimately their are similarities between an airplane and a Frisbee. While it may just look like a simple disk to have fun throwing, their is actually a lot of physics behind the creation and design of it.
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