Jump to content

ZZ

Members
 View Profile  See their activity

  • Posts

    34

  • Joined

  • Last visited

  • Days Won

    1

 Content Type 

Blog Entries posted by ZZ

  1. ZZ
    Kobe Bryant just retired after 20 years at the Lakers. As a player straight from high school into the NBA he has set many records and is arguably one of the best basketball players of all time. One thing that him and other basketball players are known for is his jumping (which might not be as good as it was 10 years ago). I figured this would be as good a time as ever to analyze his jumping skills in two videos - one of him jumping a pit of snakes and dunking a ball, and of him jumping over a car (in my next blog post). Many believe that neither were real, so I'd like to discuss the physics of both stunts.
    So the video above is of Kobe jumping a pit of snakes (I'd assume not venomous since other people were in the pit before him). After some statistics were found on this, it was calculated that his vertical acceleration was -9.56m/s^2, which is close enough to an object's acceleration due to gravity (9.81m/s^2). This evidence points to it being real, since air resistance should account for a decreased acceleration in either direction.  After scaling Kobe to the pool it can be concluded that the pool is about 12 feet across. Using various displacement measurements, The horizontal velocity of Kobe can be determined to be a little less that 12 mph - a realistic velocity as well.  Given the two data sets I can only assume that this jump could be realistic, since Kobe Bryant has a crazy amount of athleticism. I think that it could be real, but this one comes down to decision making - and I'm not sure Kobe would risk anything on a stupid (yet interesting) stunt.
  2. ZZ

    Bicycle Kicks

    By ZZ,

    The other day I was watching a soccer game, West Ham United vs Arsenal FC. I know I do blogs on soccer all the time but it's because I am just so fascinated by the things these players are able to do, hence why they are professionals. One of the players, Andy Carroll scored a bicycle kick, where a player flips himself/herself upside down with their foot in the air and kicking it over their head (sometimes referred to as an "overhead kick"). While this one was good, it reminded me of one from several years ago that another professional, Wayne Rooney performed in a game. Here's the video:
    While this goal may still have you in awe (this happens maybe once every several years by the way), I'd like to start talking about the physics. So it all started with the crosser, Nani, who crossed the ball in at about 22 mph (the speed of an average cross). This speed of the ball means the reaction window for Rooney was microscopic, even to just put the ball on target - much less the upper corner of the net. A half second too quick or too slow and this bicycle kick will end up on the blooper section of sportcenter. Upon timing the jump, Rooney is in the air for about 3/4 of a second, meaning the margin for error is quite small. Rooney's foot has also been measured to be 1.80 meters above the ground (5'9") which is about the same height as Rooney. So you might ask, what is the advantage of doing this if he could've headed the ball instead? While this is normally what players do in this scenario, a header simply wouldn't have provided the same force (and thus acceleration) on the ball. This is because of the net torque on the ball. With a header, one really only uses a little less than half of their body to cock back and snap into the header to deliver a net force upon it. However, with a bicycle kick the whole body is involved. Since the body in midair experiences no outside forces, it acts as if it were a rotating object, where both halves of the body contribute to a clockwise motion to allow a well powered kick.
    In addition, you will notice that he kicks one leg first and then the other. This has to do with momentum. as he generates momentum in one direction, this allows him to change the motion with the other leg and allow a greater velocity with his kicking leg before it makes contact with the ball. 
    All in all this stands as one of the best premier league goals of all time, ask anybody. It's really cool now to understand how Rooney did this (I know I never could)
  3. 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!

  4. 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.

     
     
     
  5. ZZ

    Pizza Tossing

    By ZZ,

    Pizza tossing is something that looks absurd at first - throwing dough into the air and spinning it around like a basketball on your finger. As it clearly takes a lot of skill, it also possesses several aspects about physics.
    Most obviously the pizza is given a centripetal acceleration of v^2/r and a force of mv^2/r and it can be treated as an object in uniform circular motion. The most  ideal motion for a single toss is a spiral trajectory. When this dough is at rest the tosser must apply a torque to give it an angular acceleration (Aang = Torque/Inertia). The ideal motion of multiple tosses is a semi-elliptical trajectory. In this case the tosser will not have the dough completely flat and it will fly through the air at an angle. This requires a ton of skill and experience on the tossers part.
    Another aspect about pizza tossing is impulse. When the tosser is catching the pizza after finishing the process, he/she obviously doesn't want to rip the pizza and start over. In order to prevent this, they must lower their hand slightly slower than the speed at which the pizza is falling in order to increase the landing time. Since impulse is equal to the Force x Contact Time, this would deliver a smaller change in momentum for the dough and lower the chance of the dough ripping.
    Lastly, the force of friction plays a big role. The addition of flour  in making the dough allows for a lower coefficient of friction and makes it slightly harder, since there must be enough friction for the tosser to thrust the dough into the air and spin it quickly, or it will end up ripping. When making the perfect pizza you must try to increase the amount of friction.
    Even though I have no idea how to toss dough in order to make a pizza, I do thoroughly enjoy consuming pizza, as it is a great bridge between all of the food groups 

  6. ZZ

    Spitballs

    By ZZ,

    So the other day at lunch when a couple of us were spitballing ideas for blogs, I figured what's better topic than spitballing itself. To test the physics of this I took a straw from the lunchroom and a smaller one from a different chocolate milk container of mine, with a similar radius. I blew projectiles (not at anyone) and found that the larger straw sent them further and faster than the shorter one. This is most likely because the longer the force I exerted on the spitball was, the larger the impulse (change in momentum) it would feel. The longer a force is applied on an object, the faster it will go and therefore the farther it will travel. It's amazing how in even the most primal of children behaviors physics can be involved.
  7. ZZ
    Yesterday I was watching soccer on TV and saw Ronaldo notch a hat trick...yet again. However, I rather began to ponder the physics behind being a goalkeeper to stop shots - maybe not as perfect as Cristiano Ronaldo's. Physics can separate the good from the great goalkeepers.
    Here are some factors in being a good goalkeeper:
    1. Momentum- A goalkeeper must have his/her weight shifted forward, standing on their toes. When a shot comes, the goalkeeper will try to save the ball while moving forward. Therefore, due to conservation of momentum, they will deflect rebounds away from the goal as opposed to in the goal.
    2. Vectors- While preparing for a shot, a goalkeeper must analyze vectors to determine a good place to stand - in the most probable path of the ball. If the forward is on the goal line (outside the goal) the goalkeeper should probably stand a step or two off his line, toward the back of the goal, to prepare for a cross (unless they have a crazy ability to curve the ball as seen in my previous blog on curve in soccer).
    3. Impulse- The best goalkeepers always buy the most expensive goalie gloves. This is because not only they can afford this luxury, but the better gloves will increase the time the force of the ball is applied for, thus increasing the impulse. Not only will cheaper gloves be much less effective in helping the ball stick, but they will reduce the amount of impact time and increase the chance of a rebound (which is a major source of goals in the game of soccer).
    I am not the best goalie clearly, seeing as I don't even play goalie, but I believe most keepers with a basis of physics knowledge would agree with me on this!
  8. ZZ

    How to Bowl a 300

    By ZZ,

    Not too long ago, over Christmas/Hannukah break, I decided to go out with a few friends and their significant others to go bowling. I went into this experience with extensive Wii bowling experience, however I hadn't touched an actual alley for about a year - the formula for success. 
    It has come to my attention that I might have been our team's downfall (we played in collective teams of 3). As I gave my ball of inertia (2/5 MR^2) an impulse to send it down a low friction alley for (hopefully) an inelastic collision at the end, I realized there was some physics involved in what I was currently doing. Upon contemplation I can definitely pick out some things I might've been able to improve on that when I go bowling again in the distant future. 
    While I attempted to throw it straight down the middle that simply did not always happen as I fed the gutter better than anyone else could've. I realized that better things seemed to happen when I threw the ball between pins 1 and 3. This is because there is apparently an optimal angle for generating strikes of about 6 degrees with respect to the lane boards. If you hit it straight down the middle, chances are, you'll end up with the deadly 7-10 split (which is nearly impossible to hit if you have next to no background in bowling). If I were to aim for this and use a little bit of curve I might've been able to get more than one lucky strike.
    When the ball is released, it first has rotational as well as translational kinetic energy due to a low coefficient of friction between the alley and the bowling ball. If we call a point at the very bottom of the ball point B, the velocity at that point would be equal to v(trans) -  ωR. Soon, the ball will stop slipping and roll with rotational KE only. I was not able to realize that in order to get the ball to hit the pins at this optimal angle, the best strategy was to give the ball rotational velocity in the x-direction as well to give the ball a curved projectile towards the pins, enough for it to last the entire pathway of 60 ft.
    If I ever go bowling in the near future I will probaby just aim to get my quota of 7 pins per turn, but it's at least cool to think about all the physics behind it.
     

  9. 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!

     
  10. ZZ

    Kobe Jumps a car

    By ZZ,

    In my previous blog I discussed the physics behind Kobe jumping a pit of snakes, which I believe is legitimate (or at least physically possible). Now I'd like to discuss another instance of Kobe's famous athleticism: him jumping over a car moving towards him. This one seems fake to me in theory because the consequences of the stunt are too much to warrant him doing it. However, I still think it'd be cool to think about the physics of it.
    This one is definitely faked. If you were to scale Kobe like in the previous video and analyze the motion. His acceleration was -6.76m/s^2. This is 3 units away from the actual acceleration due to gravity. So something is telling me that there were strings of some sort attached to him allowing him to jump with a longer hang time and avoid the car. Could Kobe do it if he were feeling bold enough? I believe in his prime, with his vertical jump, he could do it. The only problem is that the car would need to be going fast. This would mean that his reaction times would need to be as close as 1/100 of a second or he would get hit or touched in mid-air. This is why I believe it is fake; it is physically possible, but in terms of probability and natural human error (please don't give me a 0 for this blog now!) I believe he wouldn't have done this.
  11. ZZ

    Ping Pong Physics

    By ZZ,

    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
  12. 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)

  13. ZZ

    The Slinky

    By ZZ,

    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.
  14. ZZ

    The Big Race

    By ZZ,

    Just yesterday in class it seemed everyone had a good time racing some cans that they though would go the fastest. However, there were a few unexpected victors in the bracket as we saw the two walk-ons: Orange Gatorade and Mr. Temple's water bottle reach the finals, with the Orange Gatorade getting the dub in 3 matches. Why was this?
    In general, we know that the higher the mass and radius of the can, the faster it will go (i.e. its Moment of Inertia). We know the moment of inertia of a cylinder is MR^2, thus the radius having a much larger impact on the can's inertia that its mass ultimately. If we judged the races by each can's moment of inertia see who would in, chances are that Miss Huppe's German Potato Salad (GPS) would've brought home the gold. However, the Orange Gatorade knocked out the GPS for some reason or another, even though the GPS has a higher moment of inertia as well as an initial potential energy. After some class discussion we realized that there was a direct correlation between the density, or state of matter inside, and the success of the can/cylinder. The proper term for this difference in thickness would be the substance's viscosity. A substance's viscosity is determined by its resistance to flow. For example, maple syrup would have a much larger viscosity than water would. Therefore, if you had two equally filled identical cans - one with maple syrup and one with water - the one with water would go the fastest each time. This is because when a substance is more viscous than another, there will be more residue on the top of the inside of the can than the other. If you were to fill a clear water bottle partially and watch it roll down a ramp, you would see that the water would settle to the lowest point of the water bottle. The Orange Gatorade's traveled faster than the GPS and all its other opponents because of its state of matter inside which allowed it the least resistance and loss in energy during its motion.
    Even when we thought we knew which was going to win, the underdog claimed the victory!

  15. ZZ

    Bicycle Riding

    By ZZ,

    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!
  16. ZZ

    Slingshots

    By ZZ,

    Something I used to love using as a kid was a slingshot. It's so fascinating that a mechanism as simple as one of these can shoot something so fast. I thought I'd go through some of the physics behind this.
    As the elastic band is stretched, the potential energy stored is similar to that of a spring. However, the longer you take to aim the slingshot, the more potential energy you lose due to heat loss (aim fast!). If you happen to be making your own slingshot you would think that using a thicker band would have a higher spring constant and thus a larger exertion of force on whatever object is being flung, right? Against what your initial beliefs might be this is in fact not true, as a tapered band will be faster than a thicker band because it is more efficient when converting the potential energy into kinetic energy for some reason. The other interesting part about a slingshot is that, like we discovered in class with the egg drop, rubber does not obey Hooke's Law that says the Force of a spring system is equal to the product of the spring constant and the displacement. The force required actually increases in a curved, exponential fashion, whereas if you graphed Hooke's law it would be linear. If you wanted to find the force of a non-hookean solid then you could, however there are several other things to consider, such as a shear modulus or a bulk modulus, that just makes it difficult and much more complicated. Using a slingshot is fun, however make sure you use it for good and not evil.
  17. ZZ

    Sledding

    By ZZ,

    Since we finally have snow and I plan on going out sledding to maintain some sort of sanity through midterm week, I thought I'd go over some of the basic physics involved. 
    In a way it's kind of like those ramp problems that we've seen far too many times with a block sliding down it. I usually enjoy building a jump about 3/4 of the way down the hill, where I will have reached a high velocity. This allows me the greatest X and Y displacement which I could indeed calculate if I measured how far I landed from it and how long I was airborne (if you're lucky you'll get maybe a second or two). Some factors that can affect this speed that you get are essentially the things that reduce drag and friction. If you get low on your chest that will reduce the drag force of air resistance because there is less of a surface area for the air to hit (F = -bAv). Also if you use a longer plastic sled you will probably get more friction than if you used a chest-style sled with a waxed bottom and this will give you a lower velocity. All of these things must be considered when attempting to achieve maximum airtime.  
  18. ZZ

    Mousetrap

    By ZZ,

    The other day I went to do my weekly chores, one of which was picking up and setting new mouse traps if needed. It turns out that today was an unlucky day for a certain rodent. I grabbed myself a new mousetrap after cleaning up the carnage from before, and began to set it. Now that I've set many before it does not seem too hard anymore, but it still requires a lot of care when handling one, since it could seriously injure an appendage if set off accidentally. I thought about it and realized that a mousetrap is really just a balancing act with equal torques on each side (F*r = F*r). The way a mousetrap is made it uses a two-lever system, in such a way that a small force exerted on the bait will trigger the trap and thus kill its worthy victim. The arm lengths have much different lengths, in that L1<<L2 and d1<<d2.  Therefore, even just a tiny extra force at the bait will be able to trigger the trap. This is why it takes so much less work to fix the trap than to set it off.
  19. 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.
  20. 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.
  21. ZZ

    Physics of FIFA

    By ZZ,

    Like Nate Charles, I too enjoy the game of FIFA that Electronic Arts puts out every year. As a soccer player, I'm not quite sure how much of it translates into real life, as many of the players are capable of things they can only wish to do in real life. While fidgeting the other day I managed to score a goal with Cristiano Ronaldo, one of the most famous soccer players, from 42 yards away. If you know anything about soccer, you'd be pretty impressed as most goals are scored inside 18 yards. I decided I'd calculate how accurate this is to his normal free kick.
    After scoring this goal I timed how long the ball was in the air in its path to the goal - about 1.26 seconds. Simply by taking the distance and dividing by time (after converting to m/s) this yields a velocity of 30.5 m/s in the x direction. I thought if anything this was quite fast, however after some research online I realized that this velocity was in fact slower than normal. Ronaldo normally takes free kicks upwards of 130km/hr (36.1 m/s), meaning that if he hit this one in a real game he would've most likely had his shirt off runnning around celebrating about 10 seconds earlier than in FIFA. For the most part I believe the game does as well as anyone could do in making the game realistic, however there are certain aspects that will make me question the laws of physics as well.
  22. ZZ
    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...
  23. ZZ

    A Purrfect Landing

    By ZZ,

    Once upon a time, in a school far far away, Mr Muz told us that a cat has a natural ability to be able to land from a building without dying. I figured, "if there's no physics explanation to this phenomenon that would be shocking."
    What confused me the most wasn't the landing, because cats can get injured from the stress put on their legs from extreme distances, but how the cat can maneuver its body in the air so quickly and that it lands on its feet. This is something humans cannot do without defying the laws of angular momentum. Let's say on a trampoline I try a flip; there's no way for me to change the direction of that flip even if I had a 20 foot drop off, unless acted on by an outside force. 
    This makes sense to most people, however you might mention that the cat isn't acted on by an outside force either, so how can it spin? It turns out, the cat has a natural ability to contort its back and legs, much like an ice skater does while spinning, to change the way it spins. To do this they shoot their hind paws out and tuck in their front paws - lowering the moment of inertia in the front and increasing it in the back. This results in a big front twist and a small twist in the back, therefore the torques will be balanced (T = Ia). Once the cat wants to stop the front twist it will push its legs back out to increase its inertia. It will also extend its back legs again to twist them and put them back under their body before impact. From here it is the cat's natural fall-breaking abilities that help it - by having a slight give when hitting the ground it increases the time the force is felt and lowers the change in momentum.
    All in all I think I learned something very valuable, that is if a cat is stuck in a tree it really shouldn't be a big deal. Rather, we should worry more about ourselves getting stuck because  we don't have a prayer of surviving a fall from more than a single story.

  24. ZZ
    There is a video from awhile back that always makes me think about how good some soccer players really are. One skill that I believe exhibits complete mastery is curving or "bending" a soccer ball from a stationary free kick (at rest). Obviously this is not just some weird thing that happens, there must be a reason that physics can explain behind it. Upon further research there is; it is called the "Magnus Effect." This is done when either a clockwise or counter-clockwise spin is imparted on the ball. In the example below, the player hits the ball with a counter-clockwise spin, creating a small air field around it that travels in the same direction. As it goes through the air there is air resistance that is exerted on the front of the ball, slowing it down, and a force on either side of this air around the ball. the air that strikes the right side of the ball is slowed down by the counter-clockwise spin of the ball and it's effect on the ball is decreased in magnitude. The force of air on the left side is tangent to the circular path of air around the ball, so there is an added spin to the ball. This pushes the air off to the right and because Newton's laws say two objects exert equal and opposite forces, the ball will push off to the left, resulting in something like the videos below.
     
     
     
     
  25. ZZ

    Badminton

    By ZZ,

    One sport other than soccer that I feel I have a skill set in is badminton. It may look somewhat easy to a first-timer but there is a lot of strategy involved as well as skill obviously. Badminton is one of the fastest sports there is, faster than soccer, tennis, and even baseball. Usually it is played indoors, if played as an official sport, since the birdie can be very easily manipulated by the weather conditions. There are four basic shots: A smash, clear, drop, or drive - all of which should be used in distinct scenarios.
    This shuttle, or birdie, is very unique because it is designed to slow down after being used by using feathers from a goose/duck; this leads to a more predictable flight path and more control on each shot. If you ever find yourself in a match and want to make it more interesting, try tucking the feathers in slightly in order to achieve a much faster shot due to lesss air resistance. It also will always travel nose first since the center of mass lies there. Badminton players (professionals of course) can hit a birdie, 200 mph or even faster. However this is because they hit it at an optimum angle of about 72 degrees, which they usually jump to obtain. This angle and technique helps to transfer as mechanical energy possible to the shuttle when being hit, and ultimately the most velocity. Usually it is played indoors, if played as an official sport, since the birdie can be very easily manipulated by the weather conditions. There are four basic shots: A smash, clear, drop, or drive - all of which should be used in distinct scenarios. Because of all these reasons, badminton may be one of my favorite sports other than soccer.

Terms of Use

The pages of APlusPhysics.com, Physics in Action podcasts, and other online media at this site are made available as a service to physics students, instructors, and others. Their use is encouraged and is free of charge. Teachers who wish to use materials either in a classroom demonstration format or as part of an interactive activity/lesson are granted permission (and encouraged) to do so. Linking to information on this site is allowed and encouraged, but content from APlusPhysics may not be made available elsewhere on the Internet without the author's written permission.

Copyright Notice

APlusPhysics.com, Silly Beagle Productions and Physics In Action materials are copyright protected and the author restricts their use to online usage through a live internet connection. Any downloading of files to other storage devices (hard drives, web servers, school servers, CDs, etc.) with the exception of Physics In Action podcast episodes is prohibited. The use of images, text and animations in other projects (including non-profit endeavors) is also prohibited. Requests for permission to use such material on other projects may be submitted in writing to info@aplusphysics.com. Licensing of the content of APlusPhysics.com for other uses may be considered in the future.

APlusPhysics Books

APlusPhysics Books

×
×
  • Create New...