The Physics of a Curveball and a Yo-yo

The Physics of a Curveball

The path of a baseball pitch mainly depends on the spin of the ball. Pitchers work for years to perfect the desired spin of each pitch. One of the most effective pitches in baseball is the curveball. To throw this pitch the pitcher must change their release angle and the movement of their hand. The desired spin on a curveball is achieved by a flick of the wrist, like turning a doorknob. When this spin

is achieved the air resistance takes over control. Because of the ball's spin, the seams gather air as the ball rotates. This causes the velocity to be different on either side of the ball. If the ball is spinning from right to left The velocity on the left side of the ball is much faster than the velocity on the right side of the ball. This air resistance causes the ball to be "pushed" to the batter's right. This movement happens throughout the ball's entire flight. Another term used in describing a good curveball is that it "drops off the table". This is because of the air resistance from the different velocities on the top and bottom of the ball. There is a higher velocity on the bottom side of the ball which causes

more stress underneath the ball. This allows the air flowing on the bottom of the ball to break away form the ball sooner. The opposite happens when at the top of the ball. The velocity is going much slower above the ball which causes the air to "hang onto" the ball for much longer. This causes the ball to do most of its curving in the last quarter of the pitch.

The Physics of a Yo-yo

The yo-yo is one of the most popular toys of all time. Although the yo-yo seems fairly simple, there are all kinds of scientific principles at work when a yo-yo is in action. The way a yo-yo works is dependant on the way the string is fixed to the middle of the yo-yo. The early yo-yos had the string tied to the axel. Newer yo-yos have the string looped around the axel allowing the yo-yo to spin freely when the string is all the way out. Before the yo-yo is released it has two kinds of potential energy. The first is the potential to fall for the point where the yo-yoist holds the toy. The second type of potential energy is from the spin that will be created from the string unwinding.

When the yo-yo is released the potential energy turns into kinetic energy. The first potential energy turns into linear kinetic energy. The second kind turns into rotational or angular momentum. When the yo-yo reaches the end of the string the head piece has relatively a lot of angular momentum. In the older model, the yo-yo will start climbing immediately. This is because of gyroscopic stability. Gyroscopic stability is when an object resists changes to its axis of rotation because an applied force moves along with the object itself. This causes the forces on the head of the yo-yo to balance and cause the yo-yo to start climbing up the string. When the axel is free spinning, in the newer design, a small tug is required to allow the yo-yo to start climbing. The new method allows for less friction giving it more kinetic energy.

One of the most popular skills a yo-yoist must know how to do is make the yo-yo "sleep". This is when the yo-yo keeps spinning at the end of the string. This allows the head to keep kinetic energy while the yo-yoist makes different shapes or does other tricks with the string. To keep a yo-yo asleep the toy must be thrown straight down and the head must have a lot of angular momentum. Yo-yo creators have been working for a long time to allow the yo-yo to sleep better. The easiest way to do this was to redistribute the weight to alter the moment of inertia. The increased moment of inertia means an increase in the yo-yo's resistance to changes in rotation, meaning the yo-yo can sleep for longer. Another approach to allow the yo-yo to sleep better was to reduce friction. This was accomplished by creating the looped string. Another way was to add bearings to the yo-yo. The approached makes it so that the string never touches the actual axis; it is strung along two tracks of bearings. The two tracks of bearings can either work in tandem to bring the yo-yo up or down or work separately to allow the yo-yo to sleep. This is done by a small tilt in the yo-yo changing the bearing's function.

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Vacuum Cleaners

Vacuum cleaners are another household appliance that most people have encountered at some point in their lives. The idea behind how a vacuum cleaner works is pretty simple.

The fan of the vacuum cleaner rotates pushing air particles forward out of the vacuum. This creates an air pressure that is higher outside of the vacuum than inside. Air particles want to move from areas of higher pressure to lower pressure. Becuase the air pressure is higher outside of the vacuum, air is sucked through the bottom of the vacuum. The air moves through the vacuum bag and is pushed back out by the fan.

As air moves through the vacuum the air particles collide with dirt and other debris on the floor or in the carpet. If there is enough friction between the colliding particles the dirt gets carried into the vacuum with the air. Vacuum bags are porous and air is able to pass through but dirt particles are to large and get caught in the bag.

Although there are many different models of vacuum cleaners, the same principles apply.

Microwave Ovens

Most people have used a microwave oven before. They're a fairly common household appliance. They can be used to reheat food or even cook some types of food. But how do they work?

Microwave ovens heat food by causing water molecules contained in food to rotate. Water molecules are made up of two hydrogen atoms and one oxygen atom. These atoms share their electrons unevenly so tat it creates a polar molecule, where one side of the molecule is positive and the other negative.

Opposite charges are attracted to each other and similar charges repel. The microwaves emitted by the microwave oven create constantly changing electric fields. As these electric fields change, the water molecules rotate so that the positive end of the molecule is towards the negative end of the field, and the negative end of the molecule is towards the positive.

As the water molecules rotate they bump into other molecules and the kinetic engery or energy of motion is increased. Kinetic energy is proportionally related to temperature. So, as kinetic enrgy increases, the temperature of your food increases and your food becomes hot.

How Does A Bullet Work?

Guns (firearms) are without a doubt some of the most common weapons found on our planet today. They range in size, style, and usage, but they all have one thing in common: bullets.

The bullet is truly an extraordinarily simple concept. By definition, the modern bullet is a steel ‘penetrator’ core surrounded by a heavier metal such as lead. Some bullets are tipped with a harder substance such as tungsten carbide in order to achieve maximum penetration, while others are designed to expand on impact, guaranteeing maximum damage as they pass through a target. Moreover, while there are as many styles of bullets as there are purposes for using them, the physics working behind the scenes remains relatively constant.

Today, most bullets come as part of a cartridge. In a cartridge round, the bullet is usually located atop a brass casing which houses the propellant and a primer/firing cap. The amount of propellant present is usually directly proportional to the size of the bullet, which itself is dependent on the task that the cartridge is designed to perform. Larger bullets generally pack more ‘punch’, but their slower flight time and increased ballistic coefficients limit accuracy. Smaller rounds tend to have higher muzzle velocities, but often lack the penetrating power of their larger cousins. Like many things in life, it is a system of tradeoffs; the trick is striking the right balance for the task at hand.

Cartridges are simple, but the devices used to deliver them to their targets can be less so. Firearms, in general, are manufactured to utilize a specific size and style of cartridge. Although they utilize a variety of loading mechanisms, some more complex than others, once a round is ‘chambered’ the processes involved are universal. When the trigger is pulled, a small firing pin strikes the primer at the base of the cartridge, causing a spark that ignites the primary propellant. The volatile propellant releases massive amounts of energy and superheated gas as it combusts, forcing the projectile at the end of the brass casing forward at immense speeds. As the bullet passes through the barrel of the weapon, grooves etched in the barrel walls cause the projectile to spin as it leaves the muzzle, thereby stabilizing its flight and trajectory.

Once in the air, a bullet immediately begins loosing velocity. However, because the projectile is so small, and is travelling at such high speeds, it maintains massive amounts of kinetic energy all the way to its target. In fact, some specially designed bullets and their firearm counterparts can fire projectiles that retain lethality, if not accuracy, at distances significantly larger than a mile, while handguns are only effective out to a few hundred meters. Nonetheless, no matter how far away a target is, or what type of round is being used, the effects of a bullet strike are often gruesome and nearly instantaneous. Causing immense damage to whatever it happens to strike, the modern cartridge round reinforces a basic tenant that we often seem to forget:

Sometimes the most effective solution is the simplest.

Club Head Speed in a Golf Swing

Swimming

During swimming, a person exerts a force pushing themselves forward in the water.  This can be done through many methods and means, although there are only four competitive strokes: backstroke, butterfly, breaststroke, and freestyle.  In all these, a swimmer's arms and hands are used to physically push the water backwards, assisted through the repetitive kicking of the feet.  The arm is rotated at the shoulder and the hand is held firmly together when pushing backwards, as water going between a swimmers finger's can significantly reduce the force created from each push.  Swimmers can increase their fluidity through the water by decreasing the drag created between their body and the water.  This accomplished through methods ranging from the shaving of all hair to wearing small low drag suits.  Professional low-drag are often thin enough that swimmers can frequently tear the suit with the wrong movement, and have become so low drag, that certain types have become banned due to unfair competition. 

Freestyle and backstrokes are the simplest strokes and have the fastest time due to their ability to move the water the fastest behind them.  Both strokes take the simplest measure of pushing water directly behind underneath them.  Butterfly strokes do not take advantage of the level created by the human arm, and instead rely solely on the rotational motion of the arm created at the shoulder's pivot point and through straight-legged kicking.  (Straight legged kicks also occur at the start of freestyle races.) Breaststrokes use the elbow and knee joints to create levers to push water around the outside of the swimmer.  This method is usually the least effective, meaning times for breaststroke races are slower than similar length races of other strokes.

There are two other major mechanics to competitive swimming: the start and the flip turn.  During all non-backstroke races, backstrokers start in the water, swimmers begin crouched back trying to create the most force and momentum to get a speed advantage in the water. The entry into the water is crucial, as the less drag one has, the more the swimmer's get translated into the speed of his initial swim.  Along with the pre-start aforementioned methods, this is accomplished by getting the body as straight as possible when entering into the pool, with arms lined up behind the head and toes pointed.  Overall, drag in swimming comparable in basics to aero drag.  The flip turn is necessary in all high school swimming events, as all events are longer than the pools they are held in. To summarize the process, a swimmer inverts his direction by causing his body to somersault forward as he converts his momentum into the opposite direction through the force his legs exerts on the wall.

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TENNIS

 

Tennis is comprised of many specific, yet integrated components, all of which are easily broken down into the basic laws of physics.  One such component is the serve.  The ball, ideally, is thrown directly upward for so that it reaches its velocity reaches zero, one second after it is released and the ball reaches height approximately one foot higher than arm's length.  This would mean that a correct toss would be thrown at an initial velocity of approximately 10 meters per second. Higher tosses create a more favorable angle to send the ball over the net, especially when coupled with persons of height.

The service swing must be exactly as precise in order to have an effective service.  The racket provides both a forward and downward force on a powerful serve.  The racket must accelerate the ball to a minimum forward velocity of 40 m/s, if and only if no downward force is applied except gravity.  Shots must travel a minimum of 39 ft to reach the net, which is approximately two ft. off the ground.  Serves with no downward force are usually undesired during competitive play, as they are not travelling with a high enough velocity to challenge the opponent.  The fastest serve ever recording was by Andy Roddick at 249.5 km/hr (155 mph).  This ball travelled the entire length of the court in 1.12 seconds as a legal serve.

After service, the ball is returned to the server by stroking through the ball with the racket.  Strokes are either forehand or backhand in nature and use the lever created in both the arm and the shoulder to create the momentum needed to counteract the motion of the served ball. Backhand strokes are weaker than forehand strokes, due to the strength of the muscles used during the stroke and the rotational ability of the levers in the opposite direction. The other main shot in tennis is the volley.  Volleys are not a stroke of the racket, but only the use of the racket to block the ball, in a partially elastic collision.  The lightweight racket strings absorb little momentum from the ball, creating the scenario for a semi-elastic collision

Serves and strokes also can travel with a considerable amount of spin.  The ball, when given this added torque, creates a low air pressure and high air pressure zone around it, which gives the ball a curved path instead of instead of a predictable straight line.  The curved path is less noticeable in tennis than in other ball sports, such as baseball and softball, as the ball travels shorter distances and goes at higher velocities.  The spin of the ball is noticeable when in tennis when the ball hits the courts and the spin gives the ball a newer pointed trajectory. 

Three types of spins cause these varying bounces: topspin, backspin, and sidespin.  Sidespin is mostly noticeable while serving, when the spin can be controlled the most, and causes correlating left and right bounces.  Topspin is created when the racket is carried over the ball, which gives the ball a forward rotation. Topspin shots cause low, fast bounces, which are the most difficult to catch up to.  Backspin shots are hit when the racket is slide under the ball, creating a slower shot.  This shot bounces back towards the athlete that hit the ball, and may result in his opponent not being able to reach it in time.

These three shots need are hit with the racket in an angular position.  Backspin shots tend to be more accurate when in the middle of the court, and require a less steep angle for execution.  Topspin shots are better hit from the baseline, and require rotation to the angle while mid-shot. Sidespin shots are hit like upright backspin shots, but work only when the ball is high and overhead.

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iPhone Touchscreen

Since its debut in 2007, the iPhone has become the one of the most well known smartphones in the world. One of the features that was unique to the iPhone when it was first released was ability to interpret touches from multiple locations on the touchscreen, also known as multi-touch. To explain how this type of touchscreen works, one first has to understand how touchscreens work in general.

In its most basic form, the iPhone touchscreen works by measuring changes in current. The screen is composed of the LCD display, a transparent conductive layer, a grid of nonconductive dots, a second conductive layer, and a protective transparent surface. When one touches the touchscreen, the upper conductive layer comes into contact with the lower layer at the location of the touch, causing a change in current in the area of the touch. By measuring the current on the screen, it can be the determined where the touch is occurring.

The difference between this type of screen and the iPhone is that the iPhone is able to detect multiple touches simultaneously. Typical touchscreens are unable to do this because they detect touches along specific axis’s or average screen wide touches. The iPhone works differently in that there is only one layer of conductive electrodes. Each of these electrodes is independent of the others, so that the system can identify multiple independent touches. This one layer of electrodes is the reason why one has to touch the screen with either their finger or another conductive surface. Your finger generates a current from the capacitative material, allowing the iPhone to determine where it has been touched.

Once a touch or touches have been detected by the iPhone, they are sent to the processing software which determines the features of each touch. This includes the size of the touch, whether movement was involved, number of touches, and location of the touch(es). Based on this information, the iPhone determines what kind of gesture was made. It sends this information to the running application which interprets it into an action in the program.

How Exactly Do Airplanes Fly?

How exactly do airplanes fly? You’d be surprised at how many people don’t know the answer to that question. The truth of the matter is that air travel has had a profound effect on our society over the last few decades, and has influenced the development of our civilization in ways that are sometimes difficult to comprehend, or even imagine. Every day, thousands upon thousands of people embark on long distance flights, while many more utilize aircraft for shorter journeys, or simply for pleasure. It is astounding, then, that so few of us question just how an airplane works. At first glance it seems like magic, and perhaps that should bother us, but the principles involved are so basic, so foolproof, that in practice we rarely find ourselves worrying about the actual mechanics of flight.

There are four principle forces that act upon an aircraft: lift, gravity, thrust, and drag. These forces tend to work in counterpart; for example, thrust is the opposite force of drag, while lift is the opposite force of gravity. Lift and thrust can be described as positive forces, driving the aircraft up and forward, although these actual directions can change with the design, purpose, and usage of the aircraft. Meanwhile, drag and gravity are considered negative forces, pulling the aircraft down and back. Similar to the two positive forces, the actual direction of these 'negative' force vectors could very well change based on whatever particular situation may arise during the process of flight.

In most cases, lift is provided by the wings, while thrust is provided by a jet engine and/or prop. Drag is a natural force occurring due to wind and air resistance on the wing, while gravity is a naturally occurring force that is common everywhere on our planet (e.g., things fall down).
Although these principles seem simple at first glance, do we really understand how they work? We do have a pretty good working knowledge of gravity, and it’s rather apparent how engines propel an aircraft through the air. But to examine and fully understand the principles of lift and drag, we must take a closer look at an airplane wing, and the airfoil design in general.

At first glance, airplane wings appear to be fairly straightforward, but once again first appearances can be deceiving. In truth, airplane wings are specifically designed and engineered to cause a difference in the air pressure above and below the wing. The principle that is utilized in this situation is otherwise known as Bernoulli’s Principle, and can be summed up as thus:
The faster that a fluid moves (our fluid in this case being air), the less pressure it generates. Airplane wings are designed so that air travels faster over the top of the wing than the bottom of the wing, creating more pressure on the bottom than on the top. This difference in pressure creates a partial vacuum over the top of the wing, causing the wing to be lifted into the low pressure area located directly above it. There’s even a nice fancy picture there for you too look at in order to better grasp the process involved.

Drag is the other principle that we may not completely understand. Believe it or not, everything has a certain mass, even the air around us. When an aircraft is propelled forward, air is forced out and around the nose of the aircraft, creating friction. It is this friction that we call drag, and it works in the opposite direction of the aircraft’s motion.

That’s it. Mostly. Four fundamental process, four basic forces, and although the principles involved are far more complicated than I make them out to be, the basic elements of flight really are that simple.