# krdavis18

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1. ## A Review and Conclusion

This year, I really pushed myself with new challenges that were difficult, but also very rewarding. I took on the challenge of a flipped classroom and learned a new way to be a student that will help prepare me for college. While at times it was a struggle to keep up, this course kept helped me prepare for college by forcing me to work on my time management skills. I think that I have a lot more of improvement to do on this, but I have come a long way from the beginning of the year. I think before I go to college, it might be a good idea to review Dr. Chew's videos and brush up on some of the proper learning techniques that he taught. Another new thing that I took on this year was completing blog posts for this class. This activity taught me a lot of new things about how what we are learning in physics applies to the real world and I really appreciate all that I have learned. Going forward, I will have to apply the math and physics of the classroom to the real world, and doing the blog posts gave me a little bit of insight into the connections between the two. Although it may have been a challenge at times to complete the necessary blog post on time, I enjoyed learning new things about the world around me.
2. ## Vortexes and Mushroom Clouds

While doing some exploring on the internet, I stumbled across this video that does a pretty decent job of explaining a crazy pool vortex that forms when you push a plate through pool water. The woman in the video lists some examples of vortexes which include water going down a drain, hurricanes, tornadoes, and air going over a plane. In the example with the plate, the difference in velocity between the water moving with the plate and the stationary water next to it causes a shear force and makes the water spin. The vortexes keep spinning because of angular momentum and minor friction. She also examines what happens when a vortex line is curved or a complete circle like in a smoke ring, bubble ring, or even the plume rising up from an explosion. This seemed interesting to me so I decided to explore more behind what creates a plume after an explosion. The plume formed after an explosion, often called a mushroom cloud, is best known for occurring after nuclear explosions. Below is a picture from WWII of the atomic bomb explosion over Nagasaki, Japan. Some simple physics can explain the phenomenon behind the forming of this cloud. When the explosion occurs, the hot burning gases which are less dense than the surrounding air, rises up fast, creating a vacuum affect that pulls cool air up into the cloud. This is called the Raleigh-Taylor instability which occurs when two different substances of different densities interact. I've included an additional video that better explains this stunning affect. Enjoy!
3. ## Galileo Thermometer

Have you ever seen a Galileo Thermometer? They are a pretty cool way of telling what the temperature is and it also serves as a cool decoration for your home. The thermometer has little glass bubbles with different color liquid inside of them. Each little bubble has a tag on them with a different reading of the temperature. You read a Galileo thermometer by reading the tag on the lowest bubble that is still floating. The way the thermometer works to change to different temperatures involves a bit of physics. An object immersed in fluid experiences two forces, the downward force of gravity and the upward force of buoyancy. In the Galileo thermometer, its the downward force of gravity that makes it work. Each of the tags on the different bubbles has a different calibrated weight, making each one a slightly different weight from the others. The liquid inside the each of the bubbles has the same density, so that when the weighted tags are added, each bubble has a slightly different density then the others due to the ratio of mass to volume. The density of all of the bubbles is very close to the density of the surrounding water. Therefore, as the temperature outside the thermometer changes, the temperature of the water the bubbles are immersed in also changes. When the temperature of the water changes, it either expands or contracts which changes its density. So at any given density, some of the bubbles will float and others will sink. So for example, if the temperature is increasing, the waters density decreases. So the bubble with a tag that says 72 degrees, for example, will have now have a weight per unit volume that is greater than that of the surrounding water rather than lighter, and it will sink to the bottom. Very neat!
4. ## Solar Street Lights

Solar street lights are becoming increasingly popular as a green alternative because they are a better value for their cost, have lower maintenance, and easier installation. But have you ever wondered how these technological advancements function? What powers it and how does it turn on at night? I decided to look into this and examine the circuits behind the lighting of a street lamp. If you look at this picture, you can see the solar panel on top of the light that charges a battery inside the circuit during the day when the sun is shining on the lamp. Then when the sun goes down, the solar panel acts as a photocell and turns the light fixture on. Photocells work by turning light into a form of energy. A better way to describe them is that they are basically a resistor that changes its resistance depending on how much light is being shown on it. As light level increases, resistance goes down and allows the current to increase in a circuit. In reality, you can dive much further into how photocells and CdS cells work, but this basic understanding is simple enough for me for now. Below I have included a picture of a simple photocell. I have also included a picture that describes how a typical circuit in a street light might work to store the energy it converts from sunlight to provide light when the sun goes down at night. For more information on how this circuit works you can visit this website: https://science.howstuffworks.com/environmental/energy/question363.htm This is a very cool concept that I hope to learn more about in the future because I would like to become an electrical or possibly environmental engineer.
5. ## Traffic Light Detection

When you pull up to the intersection to turn onto my street, the traffic light is able to detect that my car has pulled up. Have you ever wondered how this is possible? I thought I'd explore more into this capability. The most common method is the use of an inductive loop which is a simple coil of wire within the surface of the road. https://auto.howstuffworks.com/car-driving-safety/safety-regulatory-devices/question234.htm This website gives a great example of how this process works. With this image as a reference, they write the following: "So... Let's say you take a coil of wire perhaps 5 feet in diameter, containing five or six loops of wire. You cut some grooves in a road and place the coil in the grooves. You attach an inductance meter to the coil and see what the inductance of the coil is. Now you park a car over the coil and check the inductance again. The inductance will be much larger because of the large steel object positioned in the loop's magnetic field. The car parked over the coil is acting like the core of the inductor, and its presence changes the inductance of the coil." For more information you can click on the link above. It's pretty cool to finally understand this process!
6. ## Hair Straightener

As a part of my morning routine, I usually straighten my hair with the Paul Mitchell express ion smooth hair straightener (sounds fancy I know) that can heat up to 410 degrees Fahrenheit in 60 seconds. This is a pretty incredible feat that certainly makes my life easier, but I thought I'd explore a little more behind the straightener's ability. After doing some research, I found that the straightener has a rated wattage of 40W and the voltage of American outlets is 120V. After doing some calculations, I found that the resistance of the straightener to be 360 Ohms. This is a relatively low power rating and high resistance when you consider that the hair dryer that I use has a power rating of 1875W. Pretty interesting stuff that I can't quite understand. Feel free to leave any comments that could help explain this! Thanks.
7. ## Electric Motors

In class we learned about how electric motors work and we talked about a couple examples of things with electric motors such as your air conditioning. To review, moving charges in magnetic fields experience forces. When the charges move perpendicular to the magnetic field, they experience a force which is applied to the wire. With electric motors, moving charges are sent through a loop of wire which creates motion when you examine the forces acting on the wire. There are several everyday household items that use an electric motor. Starting off in the kitchen, the refrigerator, the freezer, the blender, the disposal, and the fan in the microwave all use electric motors. In other areas of the house, the ceiling fan, bathroom fan, the garage door opener, the hair dryer, the washer and dryer, the vacuum cleaner are other examples and the list goes on and on.
8. ## Hard Boiled vs. Raw Eggs

Do you know how to tell the difference between hard boiled eggs and raw eggs without cracking them open? A common method for determining the difference is spinning the eggs on a table. If you do this, you will notice that the hard boiled egg will spin faster and then raw egg will slowly wobble around. This can be explained by simple physics. In a raw egg, their are different substances inside that each have a different inertia. Thus when a torque is applied to the egg, the substances rotate at different speeds resulting in a wobbling motion more than a spinning one. When you spin the hard boiled egg, it spins as one solid unit, thus the hard boiled egg has more inertia and spins easily and longer. Here is an eggcellent video demonstrating this.
9. ## Bowling Ball vs. Trampoline

Have you ever wondered what it would take to break a trampoline? Well in a video from How Ridiculous the YouTubers explored which would prevail a bowling ball or a trampoline. The video is pretty cool to watch and they do some fun shots in slow motion too. However, there is also a lot you can learn from their experiment. You can analyze the velocity of the bowling ball as it hits the trampoline using physics to find that its final velocity is 29.7 m/s. You can also analyze the forces acting on the trampoline using Hooke's Law. Hooke's Law proves why the bowling ball goes so high on the last drop shown in the video in which they added several golf balls and an additional bowling ball to the trampoline. According to Hooke's Law, F=-kx the heavier the force on the trampoline, the longer the springs extend. Thus the dropped bowling ball is propelled back into the air with a greater force and can reach a greater height. In another video, they also dropped watermelons and a large block of ice on the trampoline, and the trampoline still prevailed. However, you can begin to see the springs being stretched to their breaking point when they dropped the ice block from 45m. I think it will be interesting to discover what object will finally cut through the trampoline.
10. ## Bend it like Beckham

As I said in my first blog post, I love playing soccer in my free time, so I thought I would finally explore some of the physics behind a really cool technique in soccer of bending the ball. Players often use this skill when taking free kicks to put a spin on the ball and curve their shot into the goal. This technique is famously used my David Beckham and the video below highlights one of the most famous moments when he used this technique to win a match in the World Cup. It's incredible to see the curved path that the ball takes when you look at the footage of the goal head on. Players like Beckham are able to accomplish this by imparting a spin to the ball. When you kick a soccer ball with the inside of your foot and you hit the ball in its center of gravity, it is going to move off in a straight line. However, if you kick the ball with the front of your foot and kick it slightly off-center and with your ankle bent into an "L" shape, the ball will curve in flight. This is because the applied force on the ball acts as a torque which gives the ball a spin. This spinning in the air then causes the ball to be laterally deflected in flight in what is known as the Magnus effect which causes the "bending" motion of the ball in the air. You can see this represented in the image below: As you can see its pretty neat to learn about the physics behind this cool soccer technique and learn something new about the game!
11. ## End of Second Quarter Reflection

Here I am again, at the end of the quarter, rushing to finish up blog posts. But that's not to say that nothing has changed. When this quarter first started out, for the first four weeks, I managed to keep up with blog posts and do one over each weekend. However, as time went on and I got further away from my disciplined state of mind, I began to fall back into my old habit of neglecting blog posts. That's not to say that I didn't have some roadblocks along the way that prevented me from doing blog posts like finishing up college applications or preparing for midterms, but I could've done a much better job staying up to date with my blog posts. This upcoming week is not only the start of a new quarter, but also a new semester and a new chance for me to improve upon my time management skills and step further away from procrastination. At the start of this year, my bad habit of procrastination was deeply rooted, so I am not surprised that it hasn't exactly been a breeze to overcome. But I am glad that I have made some progress this quarter and I hope to continue to grow and learn and stay ahead of the game in this next quarter.
12. ## Popcorn

Popcorn is probably my favorite snack ever. But how does a small hard kernel turn into this fluffy, buttery treat? Here is what I learned: Popcorn kernels have a hard shell on the outside, but on the inside there is moisture and starch. Thus when you put a bag of popcorn in the microwave, the kernels inside start to heat up and the moisture within the kernels turns into steam. The steam then tries to escape, but is blocked by the hard outer shell. The pressure that builds up from the steam trying to escape causes the kernel to explode and the delicious white fluffy part that you eat is formed during this reaction. You can learn more about this from this video that I watched: But when the kernel pops, it doesn't just go straight up into the air. It does a sort of somersault when the pressure from the water vapor is released. Scientists captured this amazing reaction of the kernels in slow motion and used physics to help them explain the causes for this type of motion. The initial parts that form act as legs that exert a net torque on the popcorn that causes it to rotate when it pops. You can watch what they found in this video below: Thanks for reading! Now I'm gonna go make some popcorn.
13. ## Game of Thrones and Physics (No Spoilers)

I have recently gotten into the tv series Game of Thrones (which is an amazing show that I would highly recommend) and I have picked up on a couple different aspects that relate to the world of physics. While some elements of the story are clearly impossible in our world, like a 700 foot high wall 300 miles long that is made out of solid ice, it is cool to note some other elements of the show that involve basic physics. For example, you often see catapults which involves the use of torque and rotation to launch projectiles into the air. Another aspect of the show that you can analyze the physics behind is archers, which you see a lot of in the show. When soldiers are told to "loose" an arrow, Newton's third law comes into play in the force applied to the bow string and the force applied to the arrow. You can also analyze the impulse given to the arrow and its motion as a projectile. I hope to explore more of the physics behind Game of Thrones in the future once I finish watching the series.
14. ## The Northern Lights

Wow so fascinating!
15. ## Disney Pixar's Up: Exposed

I love Disney Pixar's movie Up for lots of different reasons, especially for its very imaginative and fun story line. But have you ever wondered how many balloons it would actually take to lift Carl's house? Well if you consider that about 1 liter of helium can lift one gram, then the average balloon that holds 14 liters can lift about 14 grams. So if I wanted to buy enough balloons to lift myself off the ground, that would require about 3,715 balloons. If we suppose that it costs one dollar to fill up each balloon, that's a lot of money. Going back to Up, if you consider the weight of the house and the fact that the house detaches from the foundation, Pixar estimated that you would need 20-30 million balloons to accomplish this. Not only is this an insanely ridiculous amount of balloons, but also an insane amount of money. With 30 million dollars, Carl could've flown to Paradise Falls in a private jet and built a mansion right on the falls. But where's the fun in that right?
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