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ZZ

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  1. ZZ

    Leaf Blowing (Pt. 2 - C.O.G.)

    By ZZ,

    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!

     
  2. ZZ

    Tis' the season

    By ZZ,

    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.

     
     
     
  3. ZZ
    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.
  4. ZZ

    Blog Numero Uno

    By ZZ,

    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.
  5. ZZ

    Rear Ending Someone

    By ZZ,

    I realize that when someone refers to a vague scenario about a "friend" who did something, people often jump to conclusions and assume they are sharing an embarrassing personal anecdote. However that does not apply at all here. Recently, I was in a little fender bender with one of my friends (his/her identity remaining undisclosed) and it was unfortunately a rear end collision. I'm not sure if I could've been in a scenario that screamed momentum any more that this one.
    If we treat this like an inelsatic collision (energy is not conserved since there is definitely energy lost to heat/friction) we know that M1V1 + M2V2 = (M1 + M2)V' assuming that they stick together for a short amount of time before braking. If we assume that the mass of our car was 2 tons (1814.37 kg) and we were traveling at about 15 mph (6.7 m/s) and that the other car weighed about 1.2 tons (1088.62 kg) and was at rest, then as a system the two would have a final velocity of about 4.2 m/s (9.4 mph). 
    When all was said and done the experience of an accident obviously was not fun, however it was a pleasure to blog about.
    (p.s. the collision below was not even close to what happened but I thought it looked pretty dumb)

  6. ZZ

    Breaking Down Doors

    By ZZ,

    Recently I was catching up on watching The Big Bang Theory. While the show rarely actual physics aside from the main character, Sheldon Cooper, I did witness something the other day that I thought might be a good topic to research. In the show, one of the characters, Howard Wolowitz's, mother fainted in the bathroom after receiving some bad news, and he had to break down the door, and he had to break down the door to get her to the hospital. His approach: run at the door full speed, shoulder first, and jump into the middle of the door with every ounce of your being - and consequently dislocate your shoulder. There's got to be a better way doesn't there? You see it in the movies all the time. Well, there so happens to be a better way to bust down a door in desperate times. However it should not be done with your shoulder, as that will only result in the same injury (since your shoulder can't handle the force you exert on the door in return), and you must know what your doing beforehand. Upon researching the proper way to bust down a door, here are the steps that I found are the most successful:
    1) Assess the door:
    Find which way the door swings open. If it is an outward swinging door then you're fresh out of luck with this method - you have a much better chance at breaking your foot. If it is an inward swinging door then try and locate the weak points of the door - the places with the weakest materials (usually near the lock).
    2) Get a stable position:
    Lean forward and place your foot where you want to kick, and where you are leaning forward at a comfortable angle. This lean will provide you an extra force on the door through gravity.
    3) Kick with your heel and hope for the best:
    Similarly to Mr. Lefler's post about board breaking, you must imagine yourself breaking through the door and not stop short while kicking. This will allow the maximum Impulse to be applied to the door, as we know J=FΔt. A greater time increases the impulse applied to the door. Make sure to drive your planted heel into the ground during the kick to provide stability and give yourself a better center of gravity. Avoid jump kicks since they take away power (you have no stability on the ground and will lose power).
    Remember it's not all about how strong you are, it's about your approach. A well placed kick will do then job every time as long as the door isn't outward swinging or made of metal. While I doubt most of us will ever employ this method, it can't hurt to have another emergency skill under your belt!

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