Blog Entries posted by zlessard
There are hundreds of ways to sustain an injury like a concussion. (getting hit by an object, falling on the floor, falling off of a tube, etc.) It may be strange to think about, but a concussion is truly caused by a basic physics concept: the law of inertia. Take the example of falling on the floor. When a head makes contact with the floor, the skull will obviously stop traveling in the direction of the floor. The brain, however, will continue moving until acted on by an outside force because it did not make direct contact with the floor. This causes the brain to keep moving until it makes contact with the skull, which causes the concussive energy to flow throughout the brain and ultimately lead to a concussion. So next time you fall off of a tube connected to the back of a speed boat and smack your head against the water at such a force that gives you a concussion, you can blame your misfortune on the fact that your brain is made up of matter and therefore influenced by the law of inertia.
Yesterday I was talking with my friends and we started talking about pitching, as I used to be a pitcher myself prior to this year. We ended up discussing how the way softball pitchers throw does much less damage to your arm than the way a baseball pitcher throws. Because of this, softball pitchers are able to throw every game, while baseball pitchers throw once every 5 days or so, and I definitely understand how much a shoulder can hurt in the days following a pitching outing. It really made me wonder why throwing the ball overhand is so much worse for the body than underhand, so I wanted to look at the physics behind it. What I found actually shows that softball pitchers are at similar risk to shoulder injuries as baseball pitchers, but that is a product of overuse. The pitching motion is definitely safer and more natural for a human body to perform than that of a baseball pitcher.
Softball pitchers are required to throw underhanded in fast-pitch games, so it is important that they do the windmill type motion with their arms in order to apply as much force to the ball as possible before releasing it. The whole time the ball is going around the "windmill", it is gaining acceleration, thus causing a faster pitch to come out of the pitchers hand. Pitchers also tend to rock slightly and lunge forward during their throwing motion, thus applying greater momentum towards the pitch. Applying all of these forward motions gives the greatest force to the ball in the "positive x-direction" and allows the ball to reach a peak velocity upon release.
So much of physics analysis on baseball pitches involves what happens to the ball as it flies through the air. It's a true spectacle to see curveballs and sliders that baffle hitters to no end. But what I'm more interested in here is the motion of the pitcher. As a baseball pitcher throws, they generally have a sort of rock in their motion, similar to a softball pitcher but usually slower. After taking a short step back, pitchers lift their legs up high and then stride towards home. This high leg kick provides a potential energy to the throw, which gets converted to kinetic energy during the stride. During the stride, pitchers begin to bring all of their momentum forward as they come closer to releasing the ball. During the stride, many pitchers use the rubber mound to push off of with their back foot, similar to how a swimmer kicks off the wall in order to shoot forward with greater speed. This push off allows the pitcher to have even greater momentum moving forward as they throw the ball. Then, once they complete the stride, pitchers release the ball towards home plate. Young pitchers are told not to go through a motion with the same force as if you were throwing if you aren't releasing the ball, as this means that their is no force acting back on you as you release, thus causing greater stress on the shoulder. If you even replace the ball with a towel, you get that force acting back on you that allows your shoulder to proceed being healthy. This "equal and opposite" force is what Newton described in his 3rd law.
So, upon analysis, although they look completely different, baseball and softball motions have certain similarities. They both apply as much momentum forward as possible, and release either directly above or below the shoulder. Stress on the shoulder in unavoidable in both situations, however softball pitchers are able to be used in much greater amounts. The thing I miss least about baseball, although I loved pitching, is the pain in your shoulder the days after pitching.
Something that I've been noticing since I was a little kid is that on car commercials, when they are showing the car driving, it often times looks like the wheels are spinning backwards and the car is going forward. It wasn't until recently that this concept was explained to me. What really causes this is the fact that the frames per second of the video camera is slightly greater than the rotations per second of the wheel. This makes it so that in each new frame that is recorded, the spokes on the wheels are a few degrees short of the position that they were in for the prior frame. This causes the illusion that the wheels are spinning in reverse while the car is going forward. This is known as the wagon-wheel effect.
Also less commonly but maybe a little bit cooler, the wheel can look like it isn't moving at all. This is caused by the same concept, except the spokes of the wheels are in the same position for each new frame, meaning the frames per second of the camera is equal to the rotations per second of the wheel, or that they have a perfect rotational symmetry. This effect is evident in the clip of the helicopter, as the rotor blade spins in a similar way to a wheel on a car. (for more on helicopters, look at my previous blog post)
If you haven't noticed this before, look out for it the next time you're watching a commercial or a movie. There's a good chance that you could notice the wagon-wheel effect, in effect.
The objective of this lab was basically to have the egg touch the paper without cracking. Our group went through many calculations and measurements in order to get a solution to this problem, and during this process we made a big mistake that went unnoticed until the application of our calculation failed miserably. We went through many measurements in order to find the spring constant of the 2 rubber bands put together. We found an experimental spring constant of many different masses hanging on the bands and then put these together on a graph in order to get an equation we could use to find the amount above the paper we needed to allow the egg to fall in order to just touch without cracking. The spring constant was found by integrating the equation given to us by the graph and plugging that value into the equation U=.5kx^2. This got us our final answer that we should give the egg 37 centimeters above the paper in order for this lab to be successful. (we decided to add a small amount to this because we realized that the punishment was greater for going 1 centimeter below, aka cracking the egg, rather than above the paper). This was where our group made a very foolish mistake. In a simple conversion, we multiplied by 1000 rather than 100. So truly through our calculations, our answer should have been about 3.7 rather than 37. When dropped based on that value of 37 cm, the egg didn’t even come close, and I quickly realized where our error came from. On a re-drop just to test if the answer we should have gone with in the actual application of the lab was accurate, the egg performed much more like how we expected to on its drop, with small human errors definitely impacting its overall performance. All in all, my group executed this lab pretty well aside from a major mistake in attention to detail. In this future we will definitely make it a point to check for any silly mistakes like that in order to avoid completely messing up a lab. Not to say our normal answer was completely perfect, but it performed much better than our original, flawed value did. Another error that I believe our group encountered, especially on the second drop, was not accounting for the weight of the tape added to secure the egg to the rubber band. This wasn’t necessarily substantial, but it was by no means negligible. Accounting for this weight wouldn’t have changed the major inaccuracy encountered on the first drop, which is why that is so much of the focus of this explanation. But on the second drop, it certainly would have helped get an even more accurate value.
One of many peoples favorite athletes is NBA MVP Stephen Curry, and for good reason. Personally, I like him for his shooting ability, so I decided to look more into this facet of his game. Curry is one of the best shooters in NBA history, and he does so with a very technically sound shooting form. For starters, his right forearm (his shooting arm) is always nearly vertical, never deviating more then 5 degrees away from vertical. Something I find interesting is that he releases the ball as he is rising, making for a much quicker release. He consistently releases the ball .05 seconds before the peak of his jump. Standing 6'3, the launch angle on his shot is around 50 degrees, sometimes higher, allowing him to avoid getting blocked by taller defenders and still having an arc that goes in at a very effective rate. The higher launch angle can also be an advantage because it turns the 18" diameter hoop into a larger target for the ball to go through, because the ball approaches at a steeper angle. This allows for more area for the ball to go through. The most remarkable part of Curry's shot is how quick his release is, as he releases the ball in about .4 seconds every time, allowing him to get shots off even when defenders are close. All it takes is mastering the basic physics to Curry's jump shot and you'll be able to make a ridiculous amount of three pointers like the man himself.
I Googled "how much force is in a single keystroke" and I'm going to trust a source that says 12.9 N. This will help me in my overall (obviously hypothetical) analysis.
Since this is my final blog post of the year I wanted to sort of wrap it up as well as possible and somehow tie in all of my other blogs. Using an online "character counter", I found out that there are a combined 50,015 characters across my 29 other blog posts, which have an array of topics ranging from pole vaulting to doomsday to Monte Alban. Not accounting for any backspacing, 50,015 is an accurate count of all of the characters I've put into these blogs. Utilizing the accepted force of a keystroke as being 12.9 N, that means I applied an accumulative 645,193.5 N to my keyboard for the purpose of these blogs. That's over 145,000 lbs of force, which seems like far too high of a number but I'm going to accept it regardless for the purpose of making this more interesting. I now wonder what type of things I could accomplish utilizing this much force that does not involve analyzing the physics behind a bladeless fan or a Mexican resturaunt.
Break 230 backboards (see blog no. 29)
Throw a football very far
Probably jump pretty high
Write 28 blog posts and have enough left over force to perfectly emulate the biting force of an adult Great White Shark
Push the ground really hard and pretend that the dent was caused by 32 1/4 Ford Explorers being stacked on top of each other.
As you can see, if I could somehow have concentrated all of the force that I put into the creation of these blogs into a single motion, then I could have pulled off some of the most incredible feats in the history of mankind. But alas, the people are left with 30 thoughtful, well crafted and occasionally humorous blog posts that will some day be hanging in a digital art gallery. Oh what could have been...
Like everyone else, this is my first blog post for Physics C. Outside of school, I really enjoy to golf, play CYO basketball, be around my friends or attend sporting events. I love to watch baseball and football, and that's how I spend all of my time that isn't taken up by calc, physics and econ. My biggest strength in school is that I generally understand things pretty quickly, but I could definitely benefit from an improved work ethic. In the future, I plan on attending college like most other kids in my position, but I really have no idea what I want to do once i get there. I am taking AP Physics C because, as I said, I really have no idea what I want to do in the future, so I figured the best way to set myself up for the future was to take the most challenging classes possible. What I do know about my future is that I want to be as successful as possible, and really intend on selecting a major that will best set me up for this. You're always told to major in something that you are passionate about, but I don't think many colleges offer a major in the arts of watching the New York Mets. Through this class, I hope to gain a better work ethic and improve on working in a setting like this where you have to learn a lot of things more independently. I also hope to understand Physics to a greater extent than I do now, because I feel like this topic could definitely be an important one for me going forward. The thing I am most excited for this year is the day I finish my final AP exam, because once that day comes I will have survived senior year. I am very anxious for the decisions I will have to make about my future over the course of this year, especially regarding college. Just saying the word college is enough to make me anxious. I am definitely excited to see what's in store for me in this course, and I look forward to writing many, many more blogs.
Last night, I watched a 30/30 (which is an ESPN documentary series that I would recommend to anybody) about the Orlando Magic, and one of the focal points of the documentary was Shaquille O'Neal, who was my favorite athlete in the world when I was a lad. If you've never heard of Shaq, he is a 7'1, 300+ lb basketball player. He was a force on the basketball court, for opponents and backboards alike. Throughout the documentary, dozens of clips were shown of Shaq shattering the glass on backboards or pulling down the hoop entirely, all of which occurred during games. This feat cannot be performed anymore because basketball hoops have been redesigned entirely in order to prevent this from happening. On the old hoops, the rim was only attached to the glass backboard, so if you could snap this off by applying enough downward force to it, you would shatter the backboard. This is something Shaq accomplished quite a few times. On the new hoops, the rim is actually attached to the beam holding the hoop up, so you would have to apply thousands of pounds of force to cause the rim to snap off and the backboard to shatter. On one dunk in particular, Shaq literally pulled the entire hoop down. The backboard did not shatter, but he pulled the entire hoop down. Shaq applied (estimated) over 1000 lbs of force (4450 N) in order to accomplish this feat. He admits that he did this on purpose in the documentary.
This feat is one that will never be replicated by a mortal, but it is fun to look back and see what such a massive individual was able to accomplish during a much simpler time.
Not too long ago, I went to play some tennis against a friend of mine. Long story short, I won 6-2 despite the fact that he's a starter on the tennis team. What truly led me to my commanding victory was my dominant forehand and my supernatural ability to get on top of the ball. I even surprised myself with my ability to get topspin on the ball and still get it to go over the net. This inspired me to look deeper at the physics of the forehand. The spin on the ball is applied by sort of "brushing" the ball rather than hitting it dead on. The racket also must be tilted at an angle in order for the ball to go over the net and have as good of topspin as possible. The rackets themselves are actually of a material that is good for making spin, as they have a low coefficient of friction, allowing them to slip against themselves and generate even greater spin on the ball. Lastly, the force applied to the ball from the acceleration of the racket by my hand are what gives the ball such mind boggling speed along with the spin. All of these factors put together are what lead to my deathly forehand return.
Having already written a piece about this glorious establishment for another class, I figured I might as well do one here. One of the things that has always excited me during my dining experiences at Monte Alban has been when some man brings out all of the plates on his arm using some strange oven mitt/sleeve hybrid. If you've never seen this, just picture plates full of food running up a guys arm. It's always a spectacle when this occurs because everyone wonders, "Who is this man and how is he pulling off such a feat?". Well this feat can be explained to any mere mortal using simple physics. The coefficient of static friction between this glove thing and the bottom of those plates is high enough to keep the plates securely on his arm and off the floor. Thanks to friction my tacos are always delivered safely.
I'd like to take this time to explain a little bit of how helicopters work, because they're really cool. Helicopters basically fly by sucking air from above the big rotor blade on top of the machine and forcing it downward with a thrust greater than the force of gravity acting on the helicopter. This allows the helicopter to get lift off the ground and fly into the air. Not only does the thrust created by the rotor blades have to be stronger than the force of gravity, or the weight, of the helicopter, it also has to be able to overcome the drag force created by the rotors. A thing about the rotor blades is that they continue spinning at the same speed the whole time. They do not slow down or speed up in order to change the height that the helicopter is flying at. The rotor blades do, however, control the amount of "lift" that a helicopter has, or the height at which it is flying, in a different way. Helicopters change their height by altering the angle at which the rotor blades make contact with the air. The pilot of a helicopter can increase or decrease the angle of the blades in order to go up or down. Another thing about helicopters is that they do not fly in straight lines, they are able to move side to side. This is also made possible because of the angles of the rotor blades. By altering the angle of each individual blade, a pilot is able to control the way in which the air contacts the blades in order to fly either to the left or to the right. Nifty stuff.
As many of my peers are likely snapping their fingers trying to find inspiration for blog posts, I'd like to describe what really causes the sound of these snaps.
The sound of a finger snapping really comes from 3 different parts of the snap. First, there is the friction sound between the middle finger and the thumb that occurs at the beginning of the snap. This part is quiet, but noticeable if you put some sort of buffer on your palm that prevents any sound from coming from there. After that comes the sound of the collision of the middle finger and the palm, and this creates sort of a slapping sound. The final and most important aspect of the sound comes from the rapid compression and then decompression of air that comes as a result of the middle finger impacting the palm. This creates the sort of popping sound that snaps are most well known for.
Snap on my physics associates, I believe in you.
For anyone that has followed golf recently, you have likely heard about Jordan Spieth's collapse this weekend at The Master's. Spieth went from having a 5 stroke lead to being 3 strokes behind, all within the course of an hour. The biggest blow came on the par-3 12th hole, in which Spieth shot a 7 and hit the water hazard twice. In watching this, you would notice that on the first stroke that went into the water, Spieth contacted the ball too far below the center of mass, causing it to go further in the air and shorter distance wise, leading to it contacting a slope. After hitting this slope, the ball took a couple bounces and ended up in the water. Then, Spieth was forced to hit his next shot from the drop zone for this hole, which was closer to the hole and the water hazard. On this attempt, Spieth did something that many casual golfers find themselves doing: he hit more grass than he did ball. This can be a beneficial thing if done in a sand trap, but on a lengthy approach shot, this killed him. The ball still went further than your average middle aged man could hit it, however the lost force on the ball from this initial contact with the grass made the ball not travel anywhere near as far as Spieth intended. This is a blunder you don't typically see from someone as talented as Spieth. He was able to salvage a 7 after hitting his next shot in a sand trap, a feat I likely would never be able to accomplish. If Spieth realized the physics implications on his ball prior to taking such a massive divot on his second shot that went into the water, maybe today we would be hearing about the 22 year old's second Master's victory.
Sticking with the theme of natural disasters following my post on tsunamis, I decided to look deeper into the physics of one of the most frightening disasters: a hurricane.
Starting off simply, a severe hurricane can have a power of 1x10^15 watts. To put that in perspective, that is about 3000 times the total electrical power generated in the entire world.
Looking more at what happens physically, a hurricane starts when air rushes in to fill a low pressure system somewhere out over the ocean. As the air rushes in, the moisture in it condenses, which causes a release of energy which in turn warms the air. This warm air then rises and pulls more air in around it. All of this air rushing towards the center of the storm is sort of like a centripetal force, but this apparent force only occurs because of the motion of the earth. All of this moving air eventually picks up a counterclockwise rotation due to this apparent centripetal force. So all of this air rushing towards the center and in a counterclockwise manner is what gives the hurricane it's defining characteristic: the high wind. Hurricanes thrive over bodies of water, but die off once they reach land due to the lack of moisture. These massive storms are still able to destroy a lot on land before dying off.
Hopefully, understanding these natural disasters will help me to remain as safe from them as possible.
Recently I saw a commercial for a phone that said that the screen of this phone could not be cracked. This got me thinking of all the stories that people have told me about their phone cracking and what truly causes this to happen. A few times I have dropped my phone and assumed that when I picked it up it would be completely shattered, but I was wrong. Why is it that a phone can shatter on a short fall, while other times it sounds as if it were hurled at the ground and it ends up without a scratch on it?
That question can simply be answered with luck. The likeliness of a phone to crack is dependent on where on the phone makes initial contact with the ground. If the phone falls directly on the face it is not very likely to crack because the impact is spread throughout the whole surface of the face. If a phone is dropped on its corner, the force of contact with the ground is much more concentrated in one area, making it more likely that the glass screen will not be able to survive the fall. A phone that falls from a short height and lands on its corner is more likely to crack than a phone that falls from a greater height and lands directly on the face.
The strength of a phone screen is dependent upon both the surface compression and inner tension of the phone. This strength determines how many blows the screen can take before shattering. Glass only shatters if the force of an impact is greater than the surface compression. So if a phone is only dropped from a short height, it is not likely that it will contact the ground with enough force to shatter the screen. You can't really measure the exact strength of a piece of glass because that is dependent upon the makeup of the glass, but you can get a pretty good idea of how strong a glass phone screen is.
The likeliness of a phone to shatter is also dependent on the surface that it lands on. It seems obvious, but a phone is more likely to crack on concrete than on a pillow because there is a greater force applied to the phone upon impact when it hits the concrete rather than the pillow.
So if you ever drop your phone and are worried as it falls through the air that it is going to crack, just hope that it falls directly on its face. Or, better yet, buy a good case for your phone. That way you won't have to worry so much about the ability of your phone to take the force of impact with the ground.
Being the big Mets fan that I am, I figured I'd do a blog in honor of the recent signing of the man that pulled off this throw, Yoenis Cespedes.
This throw is so ridiculous it's almost hard to believe that it's real. It is real, so lets look deeper into this.
Judging by the distance of the fence down to that corner, I can estimate that Cespedes threw this ball about 320 feet (97.5 m), and I'll make the assumption that the ball came out of his hand at about 95 MPH (42.5 m/s). This means that, counting air resistance, the ball left his hand and reached the catchers glove in a little more than 3 seconds. The runner going towards home was about 70 feet from the plate when Cespedes released this ball, and the ball reached the catcher just an instant before the runner got there. This means that had the runner been going at all faster than 7.1 m/s (15.9 MPH), then the throw wouldn't have been on time.
The launch angle of this throw was roughly 13 degrees. A 1 degree change in the vertical trajectory of this throw would have either made the ball sail above the catcher or bounce in front of him, making it much more difficult to tag the runner. Also, had the horizontal angle at the release been changed by a single degree, the ball would have traveled further to the left or right of the catcher, likely making it impossible to tag the runner.
Making a throw that far, at that high of a speed, and that precise of accuracy makes this a pretty incredible throw by Cespedes, and there is a very small amount of people on the planet that could pull this off.
As a fan of the Olympics, I often find myself watching the track and field events whenever the summer Olympics comes around. One event that particularly fascinates me is the pole vault. It seems like such a tremendous skill to pull off and I honestly wonder how people do it. If you haven't seen it, basically a competitor runs at full speed with a large pole in their hands, and once they reach a certain point they stab the pole in the ground and attempt to physics themselves over a bar set high up in the air. In short, the kinetic energy (1/2mv^2) of the individual in sprint is converted to gravitational potential energy (mgh), thus making them go as high as possible into the air. While in the air, a competitor contorts themselves in order to get over the bar without contacting it, which I believe would be a fault. In doing this, they change around their center of mass to points both above and below the bar, at times, in order to get their entire body over the bar. Once over the bar, the pole vaulter lands on a large mattress type thing, that applies an impulse to the vaulter upon landing that is too small to provide any bodily injury to the individual. So thankfully, competitors are able to pull off this feat of physics over and over again for our entertainment.
"What would be a cool blog post idea?"
The only suggestion I received was slap shots, which I decided to change to just hockey in general.
I am not a very big hockey fan, but upon hearing this I definitely felt like this could be a very cool blog. Initially all that popped into my head was the thought that the coefficient of friction of ice obviously makes for a sport not all that similar to any other sport. Diving deeper into the subject, I learned that my initial reaction was very much true, but there's a lot more interesting physics going on in this sport.
One of the most important skills to possess for any hockey player is the ability to shoot the puck, for obvious reasons. For any shot, a player is required to apply a force to the puck that is much larger than the very small frictional force being applied on the puck by the ice. An important aspect to any shot is getting lift on the puck in order to avoid the goalies attempted saves. Players are able to create this lift because the blades on hockey sticks have a small "tilt" angle, similar to that of a driver in golf. Blades also have a curve to them that allows a player to put spin on the puck. The greater the follow through on a shot, the greater the launch angle and more spin will be placed on the puck. Spin on a puck allows for it to be more stable and accurate during its flight. On a slap shot, the force applied to the puck is much greater, allowing for a much faster but less accurate shot attempt.
Once a puck is in the air, it's traveling with a parabolic projectile motion. A player wants the puck to enter the net while it is still going up in its projectile motion (before the velocity vector in the positive, assuming up is positive, y direction reaches 0), because this makes a shot more difficult to save, and also likely means that the x component of its velocity has not decreased by too much due to the force of air resistance acting on it while it flies through the air.
Knowing a lot of the physics of hockey should be helpful for any of my future endeavors in this sport. If only knowing the physics could teach me how to skate.
Something that I am definitely interested in doing in my life is going skydiving. Like many other amateur skydiving enthusiasts, I assume that the best way to start my expedition from 10,000 feet would be to understand the physics behind the fall.
Every great skydiving adventure starts with a voluntary jump into the sky. Once having jumped, a skydiver accelerates downwards until they reach terminal velocity, where the force of air resistance prevents the force of gravity from accelerating the subject any further. A subject falling in a spread eagle position will reach terminal velocity faster than someone falling head or feet first. At a certain point, the falling person must open their parachute in order to decelerate themselves in their descent. A parachute works to decelerate a falling human because it increases the cross-sectional area of the falling person, which in turn leads to an increase in air resistance, which should slow the parachute utilizer to a speed that allows them to make contact with the ground with a force that does not break every bone in their body. This device allows for people everywhere to enjoy the sensation of falling to their death without actually falling to their death. Unless of course your parachute fails to open and you have no back up. In that case you should try to land on your feet and hope the damage is small.
While searching through the internet, I came across and article from the NY Post that claims that "a killer planet is heading rapidly toward Earth". This information sounded like something that should be on every screen in the country right now, but I hadn't heard another word about it. I decided to look more into it.
It turns out that this information was originally published by a retired astrophysicist, stating that this ninth planet in our solar system periodically unleashes comet showers on our planet, roughly every 27 million years. This is pretty frightening information, if true, however it looks as though this is just another click bait article. The astrophysicist himself even said that it is "quite impossible" for any imminent damage to be done on our planet by this planet. Also, looking deeper into the research, one would find that it is a still incomplete project that has been going on for more than 30 years.
What I take away from this is that if you want the best opportunity to cause panic among people with a tabloid headline, become an astrophysicist.
For myself and the thousands of other people that simply golf for fun, one of the most frustrating parts of the game is putting. It seems like it should be so easy to line up a putt and hit it in the hole, but it is truly one of the hardest and most important part of the game. Not only is it important, it's also far different from any other aspect of the game, and this can be seen in the physics of the putt.
For starters, basically any other good shot in golf is hit in a projectile motion. The ball is hit high in the air and comes down much further down the fairway or the green or in the rough, depending on how well the ball is struck. Putting is different because the ball generally doesn't leave the ground, although it could for a split second on much longer putts with more force applied to it. The reason the putter doesn't hit the ball into the air the same way that all the other clubs in golf do is because the putter head is a nearly flat surface where it makes contact with the ball, although they usually have a very slight angle to them, while the heads of any other club are angled a great amount in order to get the necessary loft on the ball.
When the golf ball is rolling, it is a sphere rolling on a flat surface, which means it is impacted by the coefficient of static friction rather than kinetic friction. In golf, there are many different types of greens. On some the ball travels very fast, some it travels very slow, some have many different slopes scattered over it and some are flat. The fast greens obviously have a lower coefficient of friction acting on the ball, and the opposite for a slow green. A majority of putting greens are not completely flat in order to make putting more difficult. This forces a golfer to voluntarily hit the ball up a slope in order to get it to go on the proper path to the hole.
Once the ball reaches the hole, the ball must be traveling at a low enough velocity in order for it to be angled properly once it goes over the hole in order to go in. If the ball is still traveling at a high velocity once it reaches the hole, the ball will likely only slightly go in the hole and hit the back lip and pop into the air, or roll right over the hole as if it wasn't even there. If it is traveling slow enough, it will be angled properly in order to fall into the bottom of the hole.
Even looking at the physics of a putt it doesn't seem too difficult, but this doesn't account for how hard it can be to line up the ball with the right path for the hole, and how challenging it is to apply the proper force to the ball in order get it moving the proper velocity. It's pretty darn hard.
Like many others, I am watching the AFC Championship featuring the Denver Broncos and the New England Patriots. Something that has caught my eye during this game has been the punting, as Denver's punter is doing quite well and consistently giving the Patriots poor field position. On one punt in particular, the ball bounced and looked like it wasn't going anywhere, but proceeded to have, as they call it in the industry, a "Denver bounce", meaning it was beneficial for Denver. This ball ended up bouncing towards the end zone and pinned the Patriots inside the 5 yard line. I've seen many other punts that have bounced in the other direction, so I wonder how random this occurrence really is and whether or not a punter can control this.
Through my research, I've determined that this is basically random. The roll of the ball depends on where on the ball contacts the ground first. If it bounces off the center, more flat part of the football, the ball is more likely to bounce straight up in the air. If it bounces more towards the pointier ends of the football, the angle of the ball at the contact with the ground will make it bounce further horizontally. The ball basically points towards where it is going to bounce in this situation, thus determining which team gets the benefit of the bounce.
So punters really can't choose which way the ball is going to bounce. In reality, they're expecting the punt to be caught, so their only real objective in kicking the ball is to have it travel far and have a lot of hang time. Hang time is really dependent on the initial velocity and the launch angle of the ball, as well as the air resistance acting on the ball through it's flight. The ball will have the least effect felt from air resistance if it is not spinning end over end.
Punting really is a unique skill, and if any punter could master the art of achieving beneficial bounces on the ends of their kicks, then they would likely be wealthy men.
In my room I have a blue exercise ball that I like to sit on or put my feet up on or basically do anything but exercise with. While looking at this ball, I remembered a video I had seen a little while ago of a child getting hit very hard with an exercise ball. The video is below if you haven't seen it.
Basically, this is one of the dumber things I've seen, but the kids obviously weren't well versed in the concept of momentum. The smaller child was gonna absorb most of the force from the collision as the larger boy was traveling much faster and I assume has greater mass. As a result of this, the child would travel in a relatively high velocity in the direction that the exercise ball boy was running. They had the right idea that the child would act like an angled projectile after the collision as they had safety bean bags set up to break his fall, however they overestimated how quickly the boy would be accelerated downwards, and I don't think they realized how close the wall was. As a result of this, we have this video.
For anyone that has watched or played baseball, hitting a homerun has to be one of the most exciting plays that can happen. Looking at this play deeper, the physics of hitting a baseball over a fence is very fascinating. One of the things that makes this play so difficult for major league hitters is how quickly the ball is traveling, and how small the area of the bat you have to hit the ball with is in order to make it travel so far. The "sweet spot" on a bat where you will likely have to contact the ball is very small, around 4-6 inches long on the bat. Hitting the ball in this spot will minimize vibrations of the bat and possibly maximize the transfer of energy between the bat and the ball. For a baseball traveling in excess of 90 miles per hour towards the batter, contacting the ball with the sweet spot of a 32-inch bat can allow the ball to leave the bat at speeds exceeding 110 miles per hour, which can cause the ball to travel as far as 475 feet, not accounting for wind and various other factors acting on the ball in flight.
Major League Baseball has begun to realize how fascinating the physics of the sport can be for fans, and has recently started to track many more of the physical measurements that occur during a baseball game, on top of just pitch speed. The league now broadcasts the distance the ball travels, the speed it travels initially after contact, and the apex height of the ball in its flight. They've also started to measure the speed that fielders and base runners run with, and the efficiency of the route that they take to the ball. All of these measurements add to the intrigue of the sport, even for people who do not understand anything about physics. This revelation in baseball shows how fascinating the physics of sports can be, for any sport.
A product that has definitely grabbed my attention lately has been the Dyson bladeless fan. I'm not only interested due to the fact that they are $300 fans, they are just really cool. The fan is made up of a hollow tube on top, with a base below that. The air that comes out of the fan is actually pulled through this base, and runs up into the tube of the fan. This tube acts like a ramp, and the air runs along this ramp and eventually is pulled to the front of the fan where the air is pushed out like any standard fan. One would expect these fans to be very noisy, which they were at first, but the second generation of these fans were made to be much more quiet. They added Helmhortz cavities in the newer designs, which allowed them to be more able to control the noise coming from these fans. These cavities are used in the engines of some cars in order to quiet the exhaust of the car. They effectively muted certain sounds that would come from the fan. Overall, these fans are something I'd be very interested in owning, if only they weren't $300 for a small desk fan.