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About Cvankerkhove

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  1. Lebron James Flopper?

    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 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, 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.
  2. 007 Physics

    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.
  3. Physics of Dunking

    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.
  4. 8-Ball Pool

    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.
  5. Rotation of a Clock

    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.
  6. Don't worry Mike. That's for next time
  7. I'd say the scariest part of catching a football is the possible change in momentum when a defender hits you from behind in the air!
  8. AP Physics C Q1 overview

    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.
  9. Physics of a Trampoline

    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.
  10. Interesting post. Not to mention the fact that when kicking the ball with your toe hurts more because it is more force over a smaller space
  11. Phootball Physics

    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!
  12. That's good stuff! How much energy would it take to go over the top of the swing and make a loop?
  13. 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.
  14. Ever seen the movie ride along? Kevin heart fires a shot gun and goes flying in the other direction
  15. Driving on the Highway

    Whether you notice it or not, there are fundamental concepts of physics on your way to the grocery store. For one thing, in an average car ride all three types of acceleration happen: acceleration, deceleration, and turning. Another thing, riding fast in a car helps me to understand concepts of inertia. When I was little, we would be traveling 50 mph down the highway, and I would throw a tennis ball in the air. The tennis ball moved with the car. I asked my dad why the ball didn't go flying to the back of the car. That was the moment I learned about the concept of inertia. Lastly, on highway 104, there is a very large round about turn. Every time we make this right turn, I feel as though I will fly to the left side of this car. Knowing physics, I now know that inertia is what makes my body feel that way, and the centripetal force of friction keeps me from doing so. I could even calculate the force felt by f=mv^2/r.