So we are coming to a close of the third quarter in AP physics, and therefore it is time for me to write one last blog about how this quarter went in class.
We continued with the E and M course, and moved rather quickly as the AP exam would be right after the end of the quarter. Electric Potential came directly after statics, and I found this quite interesting, paticulary derivations concerning Gausses Law. Furthermore, we moved on to circuits and personally this was probably my favorite unit of the course. I really enjoyed learning about RC Circuits and how capacitors and resistors interact in a circuit; we did a lab using a bread board and Logger Pro software and this was very interesting in seeing how a capacitor discharges.
Lastly, we got into magnetism, and inductance. The main thing I got out of magnetism in this course is the chicken and egg paradox with electricity and magnetism. They are one in the same as a moving electric field creates a magnetic field, and a magnetic field can induce a current. It's all about moving charges! Furthermore, I enhanced my understanding with the Bio Savart Law and the more simpler Ampers Law.
All in all, this course has been my favorite out of my high school career, and I am ready to kill it on his AP exam in may. I would also like to thank Mr. Fullerton for the extension on the blog assignment.
I watched a video from the YouTube account MinutePhysics and it was very interesting about conservation of energy, and staying warm in a cold climate. This video was similar to the one I wrote about in an earlier blog about it it's better to run or walk in the rain.
Anyway, the video basically explained that when a person is in a very cold situation, the surface area of they're body exerts almost a protective layer of heat around they're body, of course they will still feel cold in freezing temperatures, however they are warming than they should be. When runnning, there is a draft force and therefore air resistance on ones body, and not only does this cool air make a person cold, a person is running away from the layer of heat their body creates. It would seem obvious to stay put then to stay the warmest right? Not exactly.
When humans run, approximately 80% of their energy exerted is converted into heat energy. This heat energy warms a body up, but is it enough to outway the new cold faced by the person, because he faster one runs, the greater he air resistance. Well it turns out in freezing weather a person would have to run about a 6 minute mile to stay warmer than staying put. Moral of he story, wear a parca!
Here is the link to he video I saw this on
I recall an episode of the Simpsons where Homer and Bart go in a "Zero Gravity Ride" on a jet. In the show, the way the ride works is the jet flies very high above the altitude of Earthy, then when it reaches maximum altitude, does a nose dive towards the surface of the Earth. If we analyze the physics behind this, we can understand that because the jet is in free fall, Bart and Homer are in free fall, and therefore its like "0 Gravity." In reality, there is still a gravitational force acting on them, but it feels like there isn't because of free fall, and the jet falls at the same rate as the things inside. This is the exact same concept of a space shuttle in orbit. When astronauts are in orbit, they aren't really in a place with Zero Gravity. They are actually in constant free fall around the Earth.
Furthermore, we can analyze the motion and actions Bart and Homer make when in free fall. one thing they do it float, but in order to move themselves a net force needs to act on them. By pushing their legs off the wall, a normal force is exerted on them and they can thus accelerate in the x direction until hitting the wall across them. Also, at one point they have a race by burping. Because burping releases gas from the system, an equal and opposite force pushes Homer and Bart in the opposite direction. This force is of course exaggerated for the purposes of the show, but the idea behind it is correct, similar to using a fire extinguisher on a rolling chair to move. Now indulge yourself in this comedic video of the scene.
So recently in physics class, we were talking about relativity and theoretical physics, and String Theory came up. Naturally, I was intrigued by this topic, and so I researched the topic a bit. Basically here is the run down:
In physics, particles can be replaced by one dimension things called "Strings." These strings propagate through space and time to interact with each other. A string is basically a quantum particle that carries a gravitational force, and therefore is Quantum gravity. Quantum gravity uses Einstein's theory of gravity using quantum mechanics. Furthermore, I watched a video on string theory where it related the creation and fission of different universes to string theory. the video compared a universe to a bubble, and we are tiny, tiny bugs on this giant bubble. A universe could form in two different ways: through either the collision of two different universes forming a new one, or the fission of one universe into two. The forming of our universe is what we have come to know as the Big Bang. This implies that if there is a multiverse of universes, we could travel to different ones. In order to accomplish this task, theoretically, we would need to use a wormhole to take a shortcut to another universe. A great example of a wormhole is to bend a piece of paper and stick a pencil through it. A wormhole is similar in that it bends space and time to create a shortcut.
In gym class we are currently in the Floor Hockey unit, and it has me thinking about all the physics behind hockey, both ice and floor hockey. First of all, in ice hockey, skating is an important feature. The coefficient of kinetic friction between skates and the ice is very, very low, it almost acts as a friction less surface. As result, when hockey players exert a force on the ground to accelerate themselves forward, the only way to stop in time is to turn the skates sideways and let the sharp skates dig in the ice to create a strong force of friction. For similar reasons, when a puck is shot, it will not slow down unless acted on by another force (usually another player, or the wall). Finally, why do goalies where so much padding? The reason is because a goalie is expected to save shots fired at them up to 150 mph. If they stop it, it will of coarse result in a very high impulse over a short period of time and therefore deliver a strong force to the goalie. For protection, pads are worn to decrease the change in momentum of the puck.
So i was watching a YouTube video and I came across an interesting concept. This gets into theoretical physics with parallel universes and stuff. So basically the Butterfly Effect states that the smallest action, such as the flap of a butterfly's wings can change the outcome of something in the world thousands of miles away. This implies then that if a person was able to go back in time, and they make one difference, they could change the future in millions of different ways. This leads me to think that there are thousands of parallel universes, some very different from ours and some virtually the same. When a choice is said to be made, both of those choices are made, kinda similar to the Schrodinger's Cat problem. As result, there are trillions upon trillions of different combinations of choices and events, each creating a different universe. Just something to think about.
Recently in our APC physics class we have been doing electricity and magnetism and therefore our labs include creating circuits with wires, resistors, breadboards and batteries. I believe one of the most important things I learned from this lab was that licking a 9-volt battery gives you a shock. I thank Mr. Fullerton for teaching me this trick. When you lick a 9v battery, your tongue acts as a conductor as it is wet and therefore electrons are free to move, both ends are touching your tongue and therefore a mini circuit is created. If you feel a slight shock, that's good: your battery is all charged up!
As basketball season has come to a close, it makes way for tennis for me, and there is plenty of physics in tennis.
First off, the tennis racket itself has engineering to allow the ball to fly with maximum velocity. Many cords are woven in the foundation of the racket, the strings have a strong tension in them and as result the hard tension allows for a ball to bounce of the racket and change direction. The rackets tensions are rated in force, specifically pounds (maybe newtons in Europe).
anyway that's just a little bit on tennis. There is plenty more such as kinematics and momentum, but that's for another blog.
So it has been break, and on a rainy day without school what can you do (other than read the physics textbook)? Go rock climbing. That's what I did recently and there is plenty of physics in it.
For starters, when a person climbs up a wall, they are doing work against the force of gravity, or the gravitational field. Therefore potential energy is gained he higher one goes up. Now energy exerted is of course lost with sound and friction between rocks and hands.
Furthermore, there are plenty of safety measures when rock climbing in a licsensed facility. Many places have people strapped to ropes in case of a fall, and to get down. Simply put, the rope is suspended over a pulley, with a person climbing on one end, and another person on the ground. The pulley helps redistribute the weight of the climbing. Once the person is ready to come down, the rope is pulled tight for the person climbing to be suspended in air. Therefore, the tension in the rope is approximately the weight of the person.
Our latest unit in gym class is archery and it has me thinking quite a bit about the physics behind a bow and arrow.
For example, first of a bow is composed of a frame of some material that can stretch. Next a stein string like material is tied to each end. The tighter the string, the higher the tension. A bow with a higher tension applies a greater force and therefore the impulse delerviered to the arrow is greater, (which of course is change in momentum). Energy is transferred into the arrow which hits a target or deer etc. other factors that come into play include air resistance and the force of gravity.
Lastly, there are bows with pulleys that redistribute the force, making it easier to pull back the arrow, but still have a great force applied. The compound bow was invented by a man with the last name Bear. Thanks Bear!
As midterms approach, quarter two is quickly wrapping up, and this means many things when it comes to Fullerton's APC class at IHS. For one thing, Mechanics is done. We are officially ready to take an APC exam (which will be our midterm, a scary and exciting thought). In this quarter, we got into rotational momentum, oscillations, pendulums and gravity. Personally I felt the gravity unit was pretty tough.
We also got our first taste of E & M, in the Statics unit. The big thing about this unit: Gausses Law. This law helps us to determine the flex and magnetic field due to Gaussian objects. Anyway, it's been quite some work, but I hope everyone is ready for the midterm. Best of luck!
In an earlier episode of what came to be an instant classic, Homer Simpson accidentally attempts to jump over the "Springfield Gorge" (most likely the Simpson's version of the Grand Canyon). Anyway, while this scene is extremely funny, there some inconsistencies to laws of physics. In this blog I am going to point out a few.
First off, when Homer first goes off into the air, he stays at the apex of his motion for about 3-4 seconds while only having a horizontal velocity. In fact, it almost seems as if Homer's vertical velocity seems to oscillate up and down. Of course, any physics student will tell you that this is incorrect, force there should be a net force of the force of gravity acting on Homer, and therefore he should have been accelerating downward (not in vertical equilibrium). Furthermore, when we get a wide-shot of Homer, once he realizes he is not going to make the jump, the acceleration due to gravity acting on him seems to increase exponentially; it certainly was not a constant acceleration and while this makes for hilarious television, it does not meet real life physical standards. Lastly, Homer actually falls down the cliff twice, and the force of the gorge and rocks acting on his body would surely be enough to kill him, but of course he is Homer Simpson, and when he wants to, he gets to decide the laws of physics.
A very popular and interesting YouTube channel I watch is minute physics, where a guy does short videos on different concepts of physics. One video I have recently watched is about whether it is better to run in the rain or to walk in the rain. In other words, which choice will get you least wet.
For one thing, the amount of rain that falls on your head is constant, as when you move out of the way of one rain drop, you move into the way of another rain drop. However, if you are the more horizontal distance that you travel, the more rain will hit you from the side. Therefore, the faster you move, the wetter you become. However, when you are trying to get from one point to the next, the amount of rain you run into will be constant (like a snowplow plowing a volume of snow, the speed it plows it does not change the amount). Therefore the answer is simple: Run. The less time spent in the rain, the better.
Credit to minutephysics (at YouTube.com)
In this blog I will write about the internet phenomenon known as the water bottle flip. This action gained popularity in high schools and colleges around the world, and national talk shows, and even in the NBA! It's time to analyze the physics behind the so appealing flip.
First of all, most of the bottles being flipped have a lower amount of water in them. They are certainly not full, about 1/3 to 2/5 full to be exact. This lowers the center of gravity, and therefore makes it easier to land the bottle. A higher center of gravity in a full water bottle would make the bottle want to tip over as the force of gravity is stronger and further from the surface. Secondly, when you flip the water bottle, based on angular momentum, the bottle will continue to rotate as result of inertia. However, the nonuniform water at the bottom of the bottle has a resistive net force down, and therefore a net torque that will cause the bottle to decelerate. As result, the bottle slows down when it reaches its upright position and has a great chance of landing opposed to a full bottle of water where the force of gravity is uniformly distributed.
Finally, I will show you the video that started this whole bottle phenomenon. It is intense.
Stephen Curry, a professional basketball player on the Golden State Warriors, is no doubt one of the greatest shooters of all time. Naturally, there is plenty of physics behind his sweet stroke. In this blog I will analyze different components of physics that relate to his game with the help from ESPN's Sports Science video on him.
First off, Stephen Curry runs down the court at 10 mph (about 4.4 m/s) and can stop on a dime in approximately 1/3 of a second. This the implies that the deceleration of Curry when he gets set for a shot is 13.333 m/s/s. Because Curry has 87 kg of mass, a 1160 N force is required for Curry to make this stop. This means that this force is being applied to Curry's shoes as a force of friction by the ground and onto his legs. Furthermore, Curry shoots the ball, on average, at an angle of 55 degrees. Opposed to an average trajectory of 45 degrees by a taller player, Curry's higher arcing shot allows for him to shoot over taller defenders. Furthermore, his ball has a smaller initial horizontal velocity because it is in the air longer. Lastly, this higher arc increases the area in which the ball can go in by 19%!
Lastly, Curry's release is wicked fast. On average the ball leaves his hand in .4s. This is the same time it takes the ball to undergo one full rotation, which implies the angular speed of the ball is 15.7 rad/s. To give a comparison, the average release time is .54s; Curry's crazy fast release is what makes him great.
On Monday, the defending NBA champions, Cleveland Cavaliers, played the runner up Golden State Warriors for the second time this season. The Cavs were looking for their 5th straight win in a head to head match up against the Warriors, however, the Warriors (with all 4 1/2 of their All-stars) handily defeated the Cavilers in this match up. The controversial play of the game was a Flagrant foul by Draymond Green on Lebron. The question is, did Lebron Flop? We can answer this question using physics and momentum.
As we know, when two objects collide, whether an elastic or inelastic collision, momentum is always conserved. Therefore, if we calculate the momentum of the players before and after the collision, we can decide if Lebron flopped or if it was all from Draymond. According to an article from Wired.com author Rhett Allain calculates the momentum of the players. Based on the players listed masses and video analysis he found that this was the data:
"LeBron before the collision = +548 kg*m/s
LeBron after the collision = -264 kg*m/s
Draymond before the collision = -362 kg*m/s
Draymond after the collision = -290 kg*m/s" (Allain, Wired.com).
Now if we use this data, the momentum before the collision was 186 kg*m/s in the positive direction, while after the total momentum of the system was 554 kg*m/s in the negative direction. Clearly this is not conservation of momentum so an external force was provided. This force was provided by Draymond legs pushing on the ground. So, yes, Lebron may have flung his arms, but Draymond certaintly did provided an extra force to push Lebron down.
Recently I watched the film 007 Casino Royale, the first installment of the James Bond series with the new Bond (Daniel Craig), and while the movie was very good (and equally dense) there were many inconsistencies with the real world, such as the statistical improbability of the cards, but this is a physics blog so I will talk about the physics of a certain action packed chase scene in the beginning.
The parkour scene takes us through a construction site. One thing I noticed is that at one point when the man being chased jumps down an elevator shaft, uses the wall to jump back and forth, and I believe that the force of friction between his shoes and the wall would not be great enough to support his jumps. Also, there is a large explosion that happens very close to the villain, and the blast would have most certainly effected him, the momentum of the explosion would be enough to carry him through the air. Lastly, James Bond makes about a 25 ft jump, rolls and then falls another 10 feet onto a metal crate which he crushes. The impulse delivered to bond would have been enough to kill him, or at least knock him out. But he just shakes it off and the chase continues.
There is plenty of physics when it comes to playing basketball, from shooting a three pointer to dunking. In this blog I will assess the physics behind dunking a basketball.
First off, you probably have to be a decent height, the shorter you are, the more force your legs will need to provide. Having a high vertical is the most important thing, however, for example Michael Jordan, one of the greatest dunkers of all time, had a 40 inch (1m) vertical. Now the initial velocity needed to reach this height (with the acceleration due to gravity at 10 m/s) is 4.47 m/s. Assuming the force your legs provide is over a time of .5 seconds, the acceleration is about 9 m/s. Given that Jordan was 100 kg, the normal force provided by the ground (created by his legs) is approximately 900 N! Clearly, there is some strong force required to jump and dunk, which is why you should never skip leg day, but more physics behind leg day another day.
Recently the iPhone game 8-pool has gained popularity as friends compete back and forth and there iMessage. Basically the game is a virtual version of billiards, and as result there is plenty of physics behind it. For one thing, because this game is virtual, friction of air resistance is non existant. Furthermore, while conservation of momentum is always conserved, in this game energy is also conserved between balls. The energy lost to sound and heat is not a factor, and therefore all energy is transferred into mechanical. Lastly, principles of conservation of linear momentum are present and shown as when you line up to hit a ball, it shows the resulting direction of the ball and the cue ball. These two directions will always form an angle of 90°, illustrating the principle of pool balls conserving momentum in both the x and y directions.
A clock is a very helpful invention and there is plenty of physics behind it. Today I am going to analyze he rotational motion behind a clock.
First off, when any hand completes one revelution, whether it means a minute, an hour, or 12 hours, the angular displacement is 2(pi) radians or 360°. This of course allows us to find the angular velocity (w). If we are talking about an ideal clock that rotates at a constant rate, we can determine that the second hand travels pi/30 rad/s. Next, the minute hand travels pi/1800 rad/s. Lastly, the hour hand travels pi/108000 rad/s. The angular velocity will be the same on every clock, but the linear speed of the outermost part will be greater the larger the clock.
Now this gets a little more complicated if we have a clock that ticks (which a lot do). The second hand does not travel at a constant velocity, rather it accelerates then decelerates, every time it travels one notch (pi/30) rad. On a certain watch I have, it takes about .3s for the hand to move one tick, meaning he acceleration and deceleration are about 9.3 and -9.3 rad/s/s. Clearly clocks are very complex but have some cool physics.
So yes, the first quarter is coming to a close meaning that all who are reading this survived a quarter of AP Physics C. Congrats! In this blog I'm going to give a quick overview of the triumphs this quarter.
This semester is mechanics, and so the course started with kinematics, the "easy" unit. We learned about how to utilize calculus to further the concepts of kinematics, how to take derivatives to find an instannous acceleration, or a integral to find the total displacement and so on. Next was dynamics, applied forces, and C level physics brought about the always ignored (and dreaded) air resistance. Using a differential equation, we learned how to derive an equation for velocity as a function of time (with resistance). Next came work, energy, and power. The major concept learned was that force= - dU/dx because work done over a distance is force x distance. Lastly, the final unit of quarter 1 was momentum and center of mass. Center of mass was not a major unit in Physics 1, however in Physics C we learned to get in depth behind proofs of why the center of mass of a uniform rod is L/2, using integral calculus.
Overall, it's been quite a task, but I'm glad I got my work done and was able to expand my knowledge in the field of physics.
A very fun activity to do on a sunny day is jump on a trampoline. Fun for all ages, a trampoline makes it easy to get major air. What exactly is behind this mechanism of a trampoline flinging a person into the air? Well let's talk physics in terms of energy.
Let's say that our reference level is where one stands on the trampoline. As soon as a person stands on a trampoline the webbing is stretched and sinks down to equilibrium. This is similar to our lab experiment of placing a mass on a vertical hanging spring. Now once a person stretches below equilibrium (by pressing down a force and/or jumping up) the fun begins. A person has a potential energy at the top of their jump, and this is converted into kinetic energy as they move, which is then turned into spring potential energy, when a person stretches below equilibrium level.
This idealogy is the basic physical concept of a trampoline. With this knowledge a person can incorporate cool and crazy tricks to do on a trampoline.
All sports have a lot of physics to them, but one sport in particular I have noticed to demonstrate principles of physics is football. Watching the NFL, the Minnesota Vikings are my favorite team, and though they had a great 5-0 start, ever since the bye week they have been slipping. Here's the physics behind their struggles.
The pass rush defense is weak. Viking blockers apply a force to the pass rushers, however, the pass rushers force is greater and able to overcome the resisting force. This causes a net force in the direction towards QB Sam Bradford, and as result he gets sacked. Furthermore, in the red zone, Bradfords passing has too much of a vertical component of velocity and not enough horizontal component. The ball is lofted and resulting in interceptions instead of scoring. Bradford needs to decrease that angle to score. Hopefully the Vikings read this post and start winning again!
So The Simpsons is one of my favorite shows of all time for it's hilarious characters and plots, and interesting story. Now cartoons are not always known for their strict following of the laws of physics (because sometimes it's just funny how fake it can be), but this particular scene I am about to analyze does a pretty good job of demonstrating a key concept: conservation of angular momentum.
In this scene, a student (Ralph) is in great peril, and so Principle Skinner attempts to save him by sending a message, however, this escalates the situation as it leads to a giant crate at the docks dropping grand piano's. First, lets analyze the physics of these falling pianos. The crate appears to be tilted up at an angle of 45 degrees with the horizontal, meaning that the piano's are accelerating down the crate at about 6 m/s/s (assuming some friction). However, what is comical is that there appears to be an infinite supply of pianos as we see 20 something pianos fall out of the too small crate. Assuming a max amount of 20 pianos, and each piano at 5443 kg, the tension in the rope supporting the crate would have to be 1,100,000 N!!!
Lastly, the Principle demonstrates conservation of angular momentum by running in a circular path around the crate. The crate then reacts and moves in the opposite direction. Because Skinner has an angular momentum in the clockwise direction, by conservation of momentum, the crate moves in a counterclockwise direction. This is also a representation of Newton's third law that for every force there is an equal and opposite reactionary force. Off course, Skinner's mass is so puny compared to the crates, it would not pin nearly as fast, but nonetheless, still hilarious.
The pages of APlusPhysics.com, Physics in Action podcasts, and other online media at this site are made available as a service to physics students, instructors, and others. Their use is encouraged and is free of charge. Teachers who wish to use materials either in a classroom demonstration format or as part of an interactive activity/lesson are granted permission (and encouraged) to do so. Linking to information on this site is allowed and encouraged, but content from APlusPhysics may not be made available elsewhere on the Internet without the author's written permission.
APlusPhysics.com, Silly Beagle Productions and Physics In Action materials are copyright protected and the author restricts their use to online usage through a live internet connection. Any downloading of files to other storage devices (hard drives, web servers, school servers, CDs, etc.) with the exception of Physics In Action podcast episodes is prohibited. The use of images, text and animations in other projects (including non-profit endeavors) is also prohibited. Requests for permission to use such material on other projects may be submitted in writing to firstname.lastname@example.org. Licensing of the content of APlusPhysics.com for other uses may be considered in the future.