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zlessard

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  1. zlessard

    Tsunamis

    By zlessard,

    Everyone has heard about a tsunami, whether that be the one that hit Japan not too long ago or some other instance. Regardless of how you've heard of these water monsters, I was interested to find out more about the physics behind these.
    Tsunamis are basically a massive scale version of the waves that we've studied throughout our physics experiences. Rather than wavelengths in centimeters and periods measured in seconds, the waves of tsunamis are measured in kilometers and their periods are measured in hours. Their wavelengths have been measured to be as large as 500 km. Interestingly enough, the speed that these waves travel at is dependent only upon the water depth and the force of gravity. In the ocean, water depth can be 5000m, and utilizing the equation that the speed of the wave = sq rt(g·H), that means that waves would travel 221 MPH at a depth of 5000m.
    Tsunamis caused by earthquakes, however, have wavelengths and periods that are determined by the size of the underwater disturbances caused by the earthquake.
    As tsunamis approach land, the water depth decreases, thus causing the speed that the waves are traveling at to decrease. The tsunamis energy flux, which depends on speed and height of the waves, remains almost constant. As the speed decreases and the energy remains constant, this causes the heights of the tsunami waves to become much greater as they approach land. Because of this effect, known as "shoaling", tsunamis can go completely unseen at water but grow rather tall as they approach land. This is why tsunamis are often characterized by their massive waves.
  2. zlessard

    Punting

    By zlessard,

    Like many others, I am watching the AFC Championship featuring the Denver Broncos and the New England Patriots. Something that has caught my eye during this game has been the punting, as Denver's punter is doing quite well and consistently giving the Patriots poor field position. On one punt in particular, the ball bounced and looked like it wasn't going anywhere, but proceeded to have, as they call it in the industry, a "Denver bounce", meaning it was beneficial for Denver. This ball ended up bouncing towards the end zone and pinned the Patriots inside the 5 yard line. I've seen many other punts that have bounced in the other direction, so I wonder how random this occurrence really is and whether or not a punter can control this. 
    Through my research, I've determined that this is basically random. The roll of the ball depends on where on the ball contacts the ground first. If it bounces off the center, more flat part of the football, the ball is more likely to bounce straight up in the air. If it bounces more towards the pointier ends of the football, the angle of the ball at the contact with the ground will make it bounce further horizontally. The ball basically points towards where it is going to bounce in this situation, thus determining which team gets the benefit of the bounce. 
    So punters really can't choose which way the ball is going to bounce. In reality, they're expecting the punt to be caught, so their only real objective in kicking the ball is to have it travel far and have a lot of hang time. Hang time is really dependent on the initial velocity and the launch angle of the ball, as well as the air resistance acting on the ball through it's flight. The ball will have the least effect felt from air resistance if it is not spinning end over end. 
    Punting really is a unique skill, and if any punter could master the art of achieving beneficial bounces on the ends of their kicks, then they would likely be wealthy men. 
  3. zlessard

    Full Court Shot

    By zlessard,

    Yesterday during my CYO game, I attempted, unsuccessfully, a full court heave to end a quarter. The ball bounced off the backboard still traveling at a high speed, so I decided to look into what type of throw I would have to pull off to make this shot.
    First of all, lets assume I took the shot 75 feet away from my target and released the ball about 6 feet above the ground. In order to make the ball travel the required distance, I had the right idea that it needed to have a higher exit velocity than usual, but in the physical analysis I totally went through in my head before shooting, I overestimated the exit velocity that I needed to put on the ball, leading to the ball bouncing off the backboard still traveling at a high speed. Had I gotten this aspect of the shot correct, the next important part of this shot was the launch angle. Ideally, basketball players like to release the ball at about a 45 degree launch angle, however on a full court shot, I simply don't possess the arm strength to pull this off. If I were able to do so, then the area the ball would have to go through the hoop would be greater. Unfortunately, I must make do with what I have. With the ball being released at a lower angle, the best way to make this shot would be to bank it in off the backboard. The force of this collision off the board would slow the ball down a little bit and allow it to go into the hoop from a steeper angle, again increasing the likeliness of the shot going in. 
    Obviously I didn't pull this shot off, but I am confident in my chances of making it next time.
  4. zlessard

    Coin fall

    By zlessard,

    If you've ever been at the top of a large building with a group of people, there's usually that one person that says "what if I spit from here?" or "what if I dropped a coin right now?". Well, people usually warn against these acts for fear of hurting a pedestrian down below. The question is, how badly could dropping a coin hurt somebody if this were to happen?
    In reality, the coin could not hurt somebody very badly. Coins are very light weight, as a penny weighs around 1 gram, and tumble end over end as they fall. Because of this, they don't pick up much speed against air resistance before reaching terminal velocity. The terminal velocity of a penny is only about 40-50 MPH. This means the coin would be traveling at a relatively slow speed as it approaches the ground. If it were to make direct contact with a pedestrians head, it would obviously hurt a bit, but would not cause significant injury, and definitely would not lead to death. All in all, dropping a penny from this height will hurt about as badly as it would if you threw it at someone's head from a short distance away. So the next time some wise guy tries to tell you you'll kill someone if you drop a penny from such a height, whip out some physics knowledge to counter their point. 
     
  5. zlessard
    Like many CYO ballers such as myself, one of the most surprisingly challenging parts about the game of basketball is shooting foul shots. It seems so simple when you see a professional do it: they spin the ball around a couple times, throw it up and it goes through the net. But looking at the physics of the elusive foul shot can possibly help explain why this task can prove to be so difficult for many. 
    For starters, a foul shot is a shot taken standing still 15 feet from the basket. The objective is to take an uncontested shot and put the 9.5" diameter basketball through an 18" diameter hoop. This obviously makes it challenging because these sizes don't leave much room for error. A major factor in the likeliness of a foul shot to go through the hoop is the launch angle of the shot. The ideal launch angle for an average sized player is about 45 degrees. For shorter players, a steeper angle will be required and the opposite for taller players. The problem for many players is that their launch angle on foul shots is too low. If your launch angle deviates 15 degrees or more lower than the ideal launch angle, then your shot will almost certainly hit the back of the rim. This does not mean it won't go in, but the likeliness of it going through is far lower than someone that launches the ball at the ideal angle. Another important factor impacting whether or not you will find success at the charity stripe is the spin put on the ball. A ball with a lot of backspin on it will decrease greatly in velocity once it makes contact with the rim due to the frictional force of contact, making it more likely for the ball to fall through the hoop rather than ricochet off. 
    Hopefully this new found knowledge will translate to your performance at the line. If not, work on perfecting that launch angle and maybe things will turn around for you.

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