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Everything posted by ZZ

  1. ZZ

    Bicycle Riding

    Recently I turned 18, and with that comes extra driving priveleges for those who did not take drivers ed. Thinking about all the years of being a kid made me ponder a time before I ever drove a car, when I would ride my bicycle. I can remember when I was younger riding my bike almost every day during the summer - wind blowing through my hair ready to go up to the high school's turf. Pondering this thought again now, there are a lot of physics applications in cycling. The bicycle takes power from us and converts it into kinetic energy by turning the wheels with an angular velocity. In addition, the bicycle is very efficient, converting 90% of the mechanical energy applied by the user into kinetic energy. Interestingly enough, automobiles only convert about 25%. Also, when you hit the brakes this kinetic energy is converted into heat energy since the force of friction causes the bicycle to slow down significantly (lower KE), depending on how hard you brake. Of course air resistance comes into play as well, increasing in force as you increase your speed. For a racing bike on a paved road, about 80% of the work done is to overcome air resistance, and the other 20% is to overcome what is called rolling resistance (higher the load, higher the rolling resistance). For very serious bicyclists, handlebars are looked at when considering air resistance. Handlebars that are wider provide more torque to the user (since we know Torque = FLsinθ). This is why bicyclists will have handlebars that are closer together than usual handlebars, to keep their arms in close so there is less resistance. This is also why they tuck their head down and wear aerodynamic helmets. Overall I'm glad that I don't have to ride my bike as much as I did before. If I were to now though, at least I would understand what i'm doing!
  2. ZZ

    The Slinky

    Most people have played with a slinky before, it goes down as one of the most classic yet simple toys of all time probably. My dad told me the other day about it being the 70th anniversary of the slinky being up for public sale. The story goes, the inventor - Richard James - thought of the idea when he was using springs to create instruments to stabilize boats in rough seas. While doing this he accidentally knocked a spring off of a shelf and watched as it fell down the stairs in a graceful manner as opposed to tumbling down. The Slinky demonstrates the effects of friction and inertia, potential and kinetic energy. Since inertia determines how resistant an object is to a change in motion, this clearly has pertinence in the motion of a slinky. This resistance to a change in motion, which is greater in metal slinkies than plastic ones, keeps the object moving down the stairs. Friction plays a role in the motion of the slinky as well because as the slinky falls down the stairs, the bottom of it does not move when it hits the next step, thus containing the object's momentum on the top part of the slinky - propelling it to the next step. There's also a clear transfer between potential and kinetic energy in the slinky's fall. As the slinky starts with an impulse from its rightful owner, it has potential energy in relation to the next step down. Once the slinky makes contact with the next step this is converted to kinetic energy which will propel it to the next step, and so on. All in all, the physics behind the slinky is relatively simple, but no one can deny that it's fun to push one down the stairs and watch it go.
  3. Tonight our CYO basketball team had its first practice and it looks like this year we'll be a force to be reckoned with amongst the other schools in our vicinity. However, I'm not sure if I can claim any part of this team's skill. I may account for 1/100 of our team's entire skill. In order to make myself feel better, I can explain why this is so using some fairly simple physics. Some undesirable facets of my game include: My layups I have a tendency to miss shots that some might consider "impossible to miss." There's an art to this. Normally, coaches tell their players to just aim for the square on the backboard and hope for the best. However this doesn't account for the speed of the basketball player running towards the basket. This speed must be accounted for, since you want the ball to just knick off the backboard and fall in the net. It's all relative motion. Therefore, you're supposed to take into consideration your speed, then add the extra desired speed when you throw the ball up, and only when done correctly will you score. My Jump Shots: Although my mid-range jump shots have signifcantly improved, this does not mean they are high percentage. Let's start with the beginning of the "jump shot." In order to provide the most efficient jump, it's best to keep your feet no further than 6-8 inches apart from each other. Then, the jump. The jump determines how much initial velocity in the Y-direction the ball will have before I launch it at a certain angle (giving it an added speed of vsinθ and vcosθ in the respective y and x directions). The value of θ, the launch angle, determines if the ball will go in or not as well. An angle too high will send the ball off the backboard (or even short), and an angle too small will send the ball under the hoop for a turnover as well. Lastly, you have to account for your momentum before the jump occurs. If you were running forward, even if you stopped, you will tend to be moving forward into your shot and your displacement from the hoop with have changed, as well as the momentum the ball has before an impulse is applied (similar to my layup issues). Jumping: Lastly, although it's quite basic level physics, jumping contains physics. It's all about the force you apply to the ground, which the ground will apply back to you - Newton's Third Law. Playing as one of the team's "Big Men," I have to jump often for rebounds and jump balls, and I often lose out because people who have been able to develop stronger jumping muscles have an advantage in that category (if they aren't taller than I am already). What I good at? I guess I'm on the larger side...
  4. ZZ

    Ping Pong Physics

    This past Halloweekend, I enjoyed playing a game of ping pong (or table tennis for you nomenclature inclined folks) with one of my fellow compadres, despite the result not ending in my favor. While some might dispute my strategies, claiming them as "unorthodox," I consider them successful for the most part and would definitely employ them to any worthy challenger. However, I will just do a basic overview on the physics that came to mind the other day when I was playing. First and foremost, Newton's First Law: an object in motion stays in motion, has obvious pertinence to the game itself. Once the ball ball is put in play, it will continue to move with a certain velocity, until acted upon by an unbalanced force (i.e. the opponent, air resistance/friction, or the table). Newton's second law gives us the relationship between net force, mass, and acceleration of an object. Since F = ma, we know that when a player exerts a larger force onto the ping pong ball, the ball will have a larger acceleration in its path of travel, and this leads to it being such a fast paced game. The last of Newton's Laws explaining motion - "For every action, there is an equal and opposite reaction" - would seem to apply as well, even though it is not very apparent through observation. Since the player hits the ball with the paddle giving it a force, the ping pong ball exerts the same force back. However, because the player and the paddle have much more mass, they don't experience the same acceleration as the ball. Lastly, Inertia plays its role as well by determining the maneuverability of the ball. Since inertia is a measure of mass, and the ball has a low mass, this allows each player to change the direction of the ball much easier than in most other sports, like tennis. Clearly, although it's nice to know all this physics stuff, it doesn't exactly help you win in ping pong... If you want to see a cool rally check this out https://youtu.be/LOynR3gj8rE
  5. In my last post I discussed the physics of leaf blowing, in the theme of the fall season we are experiencing currently. This weekend, while I continued the struggle of doing leaves at our foliage ridden house, I had to blow off the roof and clean the gutters using the leaf blower. While I'm not afraid of heights like some people are, I do realize the danger of being 20-30ft above the ground on a surface sloped toward my certain demise. In addition to the force I feel down the slope, which we know is mgsinø, I also had to account for the force of the leaf blower which I was using to blow the leaves up and over the roof. While I knew this would not be the safest method to blow leaves off, since I would have the force of the leaf blower and the force due to gravity pushing me toward the end of the roof, I did it anyways so that the leaves would end up in the forest behind the house. However, out of instinct, I made sure to crouch down low to achieve was most refer to as - a lower center of gravity. Center of gravity can be defined as the point at which we can consider the weight of an object to be concentrated. The lower one's center of gravity is, the higher its stability is. To increase my stability, I increased the area of the base supporting me by going down on all four. In addition to increasing the area of my base of support, lowering my center of gravity by crouching makes falling over more difficult. I managed to stay in what they call "stable equilibrium." An object in "stable equilibrium" will tilt and return to its original position, whereas an object in "unstable equilibrium" will tilt and then fall over. An example pertaining to center of gravity that most people can relate to is tipping over a coffee mug vs a tall dinner glass. Assuming the two have roughly the same mass and base area, why is it harder to tip over the coffee mug? It's because the coffee mug has a lower center of gravity. If you were to tip both cups, the tall dinner glass's center of gravity would cross its base before the coffee mug would, hence why it has a higher center of gravity and is easier to tip over. This is why when we want to become more stable, we lower our center of gravity to avoid tumbling over. Luckily I finished the job well, and lived to tell the tale!
  6. ZZ

    Tis' the season

    Greetings Comrades, Fall has many seasonal activities that come with it. One of these that I find rather unpleasant is raking/blowing leaves, due to its apparent futile nature. This past weekend, since my dad purchased another leaf blower, we were both able to use one and cut the time in half nearly to do our house's leaves. However, using a leaf blower can be frustrating due to the forces of air resistance and wind, which take away a substantial amount of kinetic energy from the leaves. Even the highest power of leaf blowers only blow at speeds of 120m/s. So theoretically, if the leaf were in the air for 1 second, the leaf should go 120m (neglecting air resistance). In this instance, air resistance causes the leaf to only go maybe 12m. Not only is it frustrating to see more leaves falling where you just cleaned up, but the fact that the leaves only go a short distance makes it even worse. Part of the reason the leaf experiences so much resistance is due to its surface area. Air resistance is largely determined by the amount of air molecules an object collides with in its intended path of travel. For example, if you took a marble and a leaf (of equal mass) and dropped them from a height of 20m, the marble would hit the ground first every time. Why is this? After doing some intense research, I believe it's because the leaf is making more "collisions" with the air molecules which slow it down more than the marble. It would take more of these collisions for the marble to reach its terminal velocity due to a lower area of contact, whereas the leaf reaches its fairly quickly. Th leaf's shape essentially causes it to be displaced less by the impulse from the leaf blower. Looks like I'll have more time to ponder such thoughts in the future, as my lawn is coated in leaves currently.
  7. As we near the end of October where most of the inclement weather begins, I'm starting feel the effects of it during our team's games. Recently, we have had games where wind has been a big factor. Wind, a form of kinetic energy, has a massive influence on the way each team must play the game. For example, if you have the wind at your back, you can take shots from further out, because the ball will experience less of a resistive net force against its path of travel while in the air - thus giving the ball a greater velocity in the x-direction. However, if your team has the wind going against you, you might not that longer shots because the wind increases the net force on the ball against its path of travel. If you had to kick the ball iin the air for some reason, it would be smartest to keep it low and hard, since the longer it is in the air, the larger the impulse felt by the ball is. In addition to the factor of wind, the moisture of the grass/turf from rain (and in a month's time: snow) is another aspect to be aware of. The wetness of the pitch conditions lowers the coefficient of friction on the ball. thus increasing the net force in the direction of travel of the ball when it is hit with a force. For a field player, this means that on a wet day, you must be a half-second on top of things because you will have less time to react to the path of the ball. You also know that you can take advantage of these conditions when shooting, and keep your shots low. If you're lucky, you can skip a shot off the ground and the goalkeeper will not be able to react in time, due to the decrease in the fricitonal force felt by the ball. As sectionals approach, these conditions will most likely play a large role in the flow of the game, since the weather at this time of the year is rarely ideal for such activities.
  8. ZZ

    First Blog Assignment

    Good looks Lessard
  9. ZZ

    Blog Numero Uno

    Alike my compatriots, this blog opens a year-long voyage through real life physics applications. I guess a good place to start my introduction would be what I do other than school (which could begin to exponentially decay in the upcoming weeks =) ). I thoroughly enjoy participating athletic activities, including Soccer, CYO Basketball, and the occasional round of Golf - even though I am utter garbage at it. I enjoy dressing well and have been told my shoe game is fire, however my friends don't like it when I wear a turtleneck. Also, if you can make a Spongebob reference in any given situation, we might be able to make things work as friends. I have several strengths in school but have just as many weaknesses; one of these could be my tendency to procrastinate (this blog post being Exhibit A). I have an older sister, Hannah, who currently is a Junior in college at MIT. I have very little idea pertaining to where I would like to attend for higher learning after high school, however I would like to pursue a career in math and/or science - thus influencing me to undertake Physics C along with BC Calculus and AP Chemistry this year. I'm well aware of the self-induced stress and pain that this means but I'm not one to turn down a challenge. Also, Physics with Mr. Powlin last year was pretty chill, so I really wanted to keep going on this tract. Through this course, not only do I hope to better my questionable time management and organization, but I hope to extend my knowledge of Physics to give me an edge when I get into college. I think the idea that you can determine the pace at which you go through the content is both a perk and a pitfall, and I hope I can learn to use it to my advantage this year, as well as use the online lectures to aid me in my endeavors this year. That is about all that I think anyone should know about me for now, godspeed fellow fizziks nerds. Looking forward to hearing about your futurenanigans and wise words.
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