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jcstack6 last won the day on October 1 2016

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About jcstack6

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  1. Dang that's a pretty insane fastball.
  2. Many people think time travel is absolutely ludicrous, but one has to consider what kind of time travel they are referring to. To travel back in time is ludicrous, because if this were ever to become possible, there would have been discovered evidence of time travelers from the future that came to our time. Time travel according to Einstein's theory of Relativity, however, is not only plausible, but true. According to Einstein, as one increases the speed at which they travel, the rate of change of time is less for them than it is for an outside observer. Based on this idea, one can travel in time by going at incredibly high speeds. By traveling at high speeds, a person will age slower than an outside observer, showing the person traveling so quickly will have, in essence, time traveled forward. So time travel backward will, most likely, never exist, but time travel forward, if great enough speeds are attainable, is fairly simple to accomplish.
  3. I feel like all my dreams of jumping the grand canyon on a skateboard have been crushed.
  4. It's all about the coefficient of friction man!
  5. Many people understand that the third pedal on a piano allows the notes to be held out for longer by not allowing the strings to be muffled inside, but the first and second pedals are a mystery. The first pedal is also a mystery to me so I won't discuss that one, but the second pedal makes the notes played softer. There is a fair amount of physics that goes into making this happen in a piano. To reduce the sound, the strings are lightly touched so that they cannot vibrate as vigorously, but not too much so that they are cut out. But why does reducing the amount a string vibrates reduce its volume? It is not because the speed at which the string rotates is reduced, but rather because its amplitude is reduced. The amplitude of a strings vibration is directly proportional to its volume. So as the amplitude is decreased by the mechanisms in the piano, the volume that the piano plays at is decreased. If anyone does know what the first pedal does, I am interested so leave a comment.
  6. In a show I recently stumbled upon, a man was told to walk the plank. This plank was nailed down, but considering a plank that wasn't nailed down, one could find the length at which to extend the plank off the ship so that it wouldn't tip over when a person with a known mass walked across it. To calculate this, one has to think about the torques applied to the plank. The torques applied, assuming the person is at the end of the plank and the plank has a uniform mass, is only the torque applied by the person and the plank. The torque provded by the person is calculated by the person's mass multiplied by the acceleration due to gravity multiplied by the person's distance from the position at which the plank is being pivoted. The torque provided by the plank is the plank's mass multiplied by the acceleration due to gravity and the plank's distance from the pivot to its center of mass. An equation can then be solved by knowing that if the plank doesn't rotate, its net torque is zero, and therefore the torque provided by the person is equal to the torque provided by the plank. By setting up this equation the position at which the plank should be placed can be determined.
  7. When looking at the sport of bowling, one can easily say the velocity at which the ball is thrown and its mass are the factors in whether or not the pins fall down, but which one matters more, or do they have the same amount of importance? When looking at this question, momentum has to be focused on. The momentum of the ball as it is thrown is what causes the pins to fall down. As momentum is conserved as each pin hits another, the initial momentum of the ball is what matters most. But what is momentum? Momentum is defined by an objects mass multiplied by its velocity. Therefore, the balls mass and the velocity at which the ball is thrown have equal amounts of importance in knocking down the pins. Therefore it's best for a bowler to pick a ball that is heavy, but not so heavy that the bowler cannot throw it with a sufficient velocity.
  8. When a skater goes into a spin, they usually start it with their arms out wide, spinning at a slow pace. Then the skater pulls their arms in and the speed at which their rotating increases and finally as the spin comes to an end, their arms extend again and they slow down. Many people understand that physics is incorporated in skating, but they don't understand how much goes into a simple spin in terms of physics. Rotational momentum is defined by the objects moment of inertia multiplied by their angular velocity. An object's moment of inertia is defined by their mass multiplied by their radius squared, multiplied by a constant determined by the shape of the object. Therefore, as a skater pulls in their arms, their radius decreases, decreasing their moment of inertia. Since rotational momentum is conserved during the skaters spin, their rotational velocity increases as their moment of inertia decreases. It is astonishing how simple something so mesmerizing can be after the physics behind it is understood.
  9. Many people spend the winter practicing thrilling winter sports such as skiing or snowboarding, but I like to stick with simplicity. Sleding requires very limited skill to still have the thrill of gliding down a hill. There is also a lot of physics behind sleding, specifically how to turn on a sled. People seem to automatically know that they should lean to a side to turn to that side on a sled, but why? It's all about the normal force. The sled glides down the hill because of the force of gravity on the sled and the person in the sled but turning is a different story. Once a person leans to the side they are push by the snow because they have rotated the snows normal force on the sled. Initially the normal force is perpendicular to the sled but once the sled is turned, the normal force is at an angle, causing the sled and the person to be pushed to the side. This is why simply leaning to the slide one wants to turn works in sleding, and the basic concept even holds true in skiing and snowboarding.
  10. Blogmas is my favorite holiday.
  11. That's so cool to think about that energy can't be lost or created even in the scenario of a massive rollercoaster.
  12. Thanks for discussing conservation of angular momentum between the balls as they role, great job.
  13. In my limited time playing tennis for school and ping pong in my free time, I've learned how to properly return a fast serve. I would always see a quick serve coming at me and be tempted to swing hard back at it, but that would always end in the ball soaring off to either side. My coach instead told me to just hold my racket still and steady and let the ball bounce off of it. This technique has a lot of physics behind it that makes sense. Think of a ball being bounced on the floor. The floor does not swing at the ball to propel it back to your hand, rather the ball merely hits the still floor and goes back up. This can be thought of an elastic collision where all of the potential and kinetic energy of the ball is conserved causing the ball to bounce back up to one's hand. Similarly in tennis and ping pong, a fast serve met with a still racket causes the ball to go across the net with the same speed as it was served with but in a controlled manner. Therefore, even though swinging at the ball will cause its speed to increase, to get a fast AND controlled return, one should cause and elastic collision with the ball and the racket by holding the racket steady and still.
  14. I often play pickup basketball with my brothers, the teams usually split up as me and Paul vs Nathan and Dave. Paul is garbage, however his terrible form and his "signature move" has a lot of physics involved with it. Paul believes the greatest shot is one where he dribbles along the three point arc and chucks up a shot one handed while falling backward. He believes the best way to make this shot is by aiming for the white square on the backboard. This is surprisingly not the best tactic however. Even though every coach tells their 5 year old players to aim for the magic white box, in Paul case, they shouldn't. Since Paul is moving sideways with some velocity, the ball is also moving sideways with the same velocity. Therefore, if Paul aims for the white box, he will end up missing it because the ball will not travel straight but slightly sideways due to Paul's velocity in the horizontal direction. Therefore, Paul should aim to one side of the white box so that the ball actually hits the white box and has a chance of going in. However, playing with Paul turns into an hour of pain and frustration.
  15. Biking is one of the most electrifying activities out there. Picking up speed as you approach a jump, wondering how much air you'll get and then being launched into the air. Not many people, however, know all of the physics behind just simply going off a jump. It can be thought of in terms of kinematics by knowing the bikers initial velocity, but then one neglects how the biker obtained that initial velocity. Rather we can consider work and energy to talk about the correlation between the force of the bike, the distance the biker accelerates, their final velocity and the height they get off of the jump. Since work is equal to the bikes force multiplied by the distance the force is acting for, and since work equals the change in kinetic energy, the greater the force or the greater the distance, the greater the bikers kinetic energy. When looking at kinetic energy of the biker, we can look at linear and rotational, but for simplicity we'll just focus on linear. Since linear kinetic energy is a function of speed and mass, the speed of the biker increases, because the bikers kinetic energy increases and the bikers mass is constant. Finally, if the biker has no potential energy before the ramp, and no kinetic energy at his maximum height, we can set kinetic energy equal to potential energy, a function of height, mass and the acceleration due to gravity. Therefore, the height a biker gets is dependent on the bikers speed, but since his speed is dependent on the bikes force and distance that the force acts, the height the biker ultimately attains is dependent on the bikes force and distance that the force acts.