# ZZ

Members

34

1

## Blog Entries posted 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:
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)
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.
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.
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.
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!
Recently I've had a little bit of a pickle fetish. However, one of the things that is inevitable for us regular pickle-eaters is the difficulty in taking of the lid of the jar.
One tip I have is to run the jar under hot water. This way the lid will become easier to turn. This is because metal has a higher coefficient of expansion than glass does. Thus, as the jar stays under the hot water, the metal expands a tiny bit, and the glass stays the same (I also find it easier to use my left hand because it's easier to turn CCW with your left than your right).
The other tip I have would be to hit the gym and organize a forearm based workout session because without the hot water trick I've got just about nothing.
Good luck in your future pickle jar opening endeavors.

Like many other students, I am looking forward to summer. One activity many people enjoy is water skiing! Water skiing has a lot of physics involved. The basics are essentially based on angles and gravity. When you get up from the start, your ski must be at a certain angle so that the water pushes down on the ski, creating a downward force that enables you to stand up (otherwise you'll just fall flat on your face). Once the forces up from the water and down on the ski are equal, you're set for takeoff!
Tension, a pulling force, is also involved when the skier holds on to be pulled by the boat. Once the tension in the rope becomes constant, you will travel at the same speed as the boat that is pulling you, since there is a constant force with no acceleration. Also, since you are usually moving in a circular path, there is also an inward, or centripetal force, keeping the you in a circular path.
Can't wait to go do it this summer!
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.
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.

Recently while fishing for some blog-worthy material I stumbled upon one of my favorite youtube channels that posts cool videos on all sorts of sciency stuff. Since magnetism is not the most heated of debates amongst us students for some odd reason, I figured a video on magnetism might spice things up a bit for me. I learned about a whole new type of manufactured magnet that I thought would look really interesting to a technology guy like me.
Now we all know about magnets, right? One end is south and the other is north. You can use put your failing grades from physics and calc tests (at least I can) up on the fridge for mom and dad to see. They're fun to play with. However they do have some other more important uses such as the ones in your refrigerator, car brakes, or screen displays.
New magnets, however, are not only beginning to be made with multiple poles on one side, but programmable polarities - meaning a pattern of polarities can be programmed on software and the magnetic field can be "printed" onto a magnet. This means that you could print as many poles in whatever shape you desire. One of the benefits of this is that a very distinct shape could be printed between two magnets and allow them to attract each other only up to a certain point. After that point they will repel and only continue to attract once aligned properly. Although it just seems cool at this point, it could be useful in door and hinge technologies, allowing easier opening and closing.
Magnetism isn't heard about often for a reason, because there's a lot we (especially me) don't know yet. However, I thought the fact that we can create magnets with multiple poles on each side, or "polymagnets," was a pretty cool thing.

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

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.
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.
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.

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.
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)

It has come to my attention that the lunches I bring to school each day are fabled to be one of the best around. This however does not simply just happen. It requires an extensive shopping trip to none other than the Irondequoit Wegmans to collect everything I might need to keep me focused during the day. I'm not going to describe all of the food I get because that would be weird and unecessary, however there is one aspect of my journey in getting the food to my house that I had never really pondered and I've done it for years. I'm not sure if I'm the only one who does this, but I do not enjoy going to and from the car several times in order to retrieve the delicacies that lie within. I'm more of a "take a trip once" kinda guy. This comes with a price: loading your arms up with groceries that weigh as much as you do (if you don't feel this sensation you're missing out). Most people just take a few in each hand, which I used to do, until I started putting the groceries higher up on my arm near my shoulder and layered them on til I had every last bag. As a youngster I just thought it was easier (since I've never exactly been a "strong" individual) and never went any further with that observation. However, now I realize that it is quite basic. It is because I am decreasing the radius that the force (weight of the groceries) is being applied to. This would decrease the torque applied by the groceries with respect to my arm significantly. Thankfully this leads to an increased blood circulation and a reduction in the number of trips I must take to bring in the groceries!
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.
Recently my social interactions led me to watching an invigorating game of men strategically sliding stones of inertia 0.5MR^2 on an iced lane with a low coefficient of friction: Curling. It's probably a sport that most of us in New York have not tried since it's not very mainstream. However, I may have to consider making a guest appearance at the most prestigious Rochester Curling Club. Watching this sport on television led me ponder the physics behind it.
Curling may be the only sport where the player(s) are allowed to affect the trajectory of the object after its release. "Curlers" use brooms to brush the ice off in front of the stone to make the surface smoother for the stone to travel on (lower coefficient of friction). I first though that the purpose of the curlers brushing the ice was to make the stone curl in whichever way they needed it to by increasing or decreasing friction on one side of the stone. It turns out that I was completely incorrect. They brush the ice to warm the ice so that the stone actually curls less. However I did figure out that unlike many objects, the curling stone curls in the direction it is spun. If you were to take a simple dinner glass and spin it clockwise while it slides forward, (don't use an expensive glass) it will end up curling off to the right. This is because it is pushing on the table with the leading edge more, delivering a greater force of friction. However, the runnning band (the concave surface of contact on the bottom of a curling stone) enables it to move in the direction it is spun - for what reason I could not conclude from my research.
The most interesting question I had was: why specifically does the curling stone "curl" on the ice? Which is apparently a hot topic amongst some physicists in curling competitive countries.
I found two interesting but not entirely proven theories: The Scratch Theory and the Asymmetric Friction Melting (ASF). The Scratch Theory says that the scratches made by the leading edge of the running band are hit by the rear edge of the band - sending it in the path of its rotation. ASF says that there is more friction on the leading edge which heats the ice more and provides more lubrication for the stone, while the back has more friction. This process would also theoretically send it in its path of rotation.
While I learned a lot more about curling and the apparent uncertainty that lies behind it, I think its a great time this winter to maybe try it out for myself!
(p.s. A "snowman" is a perfect score of 8 because it looks like a snowman. If you want to learn more in depth about it check out this link. It taught me a lot! https://youtu.be/7CUojMQgDpM)
Recently my social interactions led me to watching an invigorating game of men strategically sliding stones of inertia 0.5MR^2 on an iced lane with a low coefficient of friction: Curling. It's probably a sport that most of us in New York have not tried since it's not very mainstream. However, I may have to consider making a guest appearance at the most prestigious Rochester Curling Club. Watching this sport on television led me ponder the physics behind it.
Curling may be the only sport where the player(s) are allowed to affect the trajectory of the object after its release. "Curlers" use brooms to brush the ice off in front of the stone to make the surface smoother for the stone to travel on (lower coefficient of friction). I first though that the purpose of the curlers brushing the ice was to make the stone curl in whichever way they needed it to by increasing or decreasing friction on one side of the stone. It turns out that I was completely incorrect. They brush the ice to warm the ice so that the stone actually curls less. However I did figure out that unlike many objects, the curling stone curls in the direction it is spun. If you were to take a simple dinner glass and spin it clockwise while it slides forward, (don't use an expensive glass) it will end up curling off to the right. This is because it is pushing on the table with the leading edge more, delivering a greater force of friction. However, the runnning band (the concave surface of contact on the bottom of a curling stone) enables it to move in the direction it is spun - for what reason I could not conclude from my research.
The most interesting question I had was: why specifically does the curling stone "curl" on the ice? Which is apparently a hot topic amongst some physicists in curling competitive countries.
I found two interesting but not entirely proven theories: The Scratch Theory and the Asymmetric Friction Melting (ASF). The Scratch Theory says that the scratches made by the leading edge of the running band are hit by the rear edge of the band - sending it in the path of its rotation. ASF says that there is more friction on the leading edge which heats the ice more and provides more lubrication for the stone, while the back has more friction. This process would also theoretically send it in its path of rotation.
While I learned a lot more about curling and the apparent uncertainty that lies behind it, I think its a great time this winter to maybe try it out for myself!
(p.s. A "snowman" is a perfect score of 8 because it looks like a snowman. If you want to learn more in depth about it check out this link. It taught me a lot! https://youtu.be/7CUojMQgDpM)
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.

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!

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!

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!
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.
×
×
• Create New...