# Physics in the Real World

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## Mousetrap

A simple snap-back mousetrap is a clever machine. With just a few parts (a wooden base, a spring, a metal bar, and a trigger mechanism) it can do its job quickly and efficiently.  When a mousetrap is set, the spring in the center is compressed, becoming a source full of potential energy. This energy is being stored, not used, but as soon as the trap is released, it is converted to kinetic energy (the energy of motion) that propels the snapper arm forward.  This is a perfect example of conservati

## Speed of Sound

The speed of any wave/the speed of sound depends upon the properties of the medium through which the wave is traveling.  But first if there is no medium for the wave or sound to go through, then there will be no sound.  For example, there is no medium in space so there is no waves/sounds travelling in space.  There are two factors that effect speed of sound.  One of them is the elastic properties of the medium/material.  Elastic properties of an object is how easily the object is able to bend or

## Ferris Wheel

A couple of summers ago, my family and I went to Hersey Park for vacation.  I'm afraid of heights but I love to go on roller coasters and I remember that there was a Ferris wheel that my sisters persuaded me to go on.  It was scary because you could see how high you were from the ground.  But it was also cool because you could see everything.  Anyways, a Ferris wheel can be related to physics because of its shape.  It is related to centripetal force and torque.  So basically, I could calculate t

## Yo-Yos

When I was a kid, my parents bought me a yo-yo. At first I was puzzled and wondered how to play with it. I spent a good amount of time practicing and I could finally make it roll and then come back to me. I thought that was a huge accomplishment, but then I saw on TV a yo-yo contest with these people doing insane tricks with their yo-yo. I never knew how they could do it. So I decided to see the physics behind a yo-yo.  I found that when people do string tricks that makes the yo-yo roll on the s

## Opticall Ilusions

Our brain are set up to receive and interpret messages from the eye. Optics, a branch of physics, studies the interaction of the light and the eye. This interaction plays an important role in optical illusions. Optical illusions use light, colors and other features to trick the mind into thinking of things that are or aren't there. For example the Lilac Chaser Illusion. In this optical illusion, the viewer sees purple blurry dots arranged in a circle around a focal point. As you stare at the plu

## Jenga

Jenga, it's the classic block-stacking, stack-crashing game that everyone played as a kid. You and the person you played with, stacked up pieces of block into a sturdy structure and then you remove these blocks from the bottom or middle and placed them on the top. As you removed a block from the structure you had to be careful of how you removed it because one wrong twist or turn, you could collapse the structure and lose. The reason why it's so hard to remove the block from the structure becaus

## Riding a Bike

Did you know that you transfer about ninety percent of your force upon a pedal of a bike into kinetic energy? Riding a bike is so simple but there is so much physics behind it. As you ride a bike there are multiple forces on you. There is a force of gravity downwards on you, so as you slow down, the force of gravity will push you and the bike down. There is also a drag force and frictional force acting on you and the bike. The drag force is the air resistance you feel when you go downhill. If yo

## Metamaterials

Could you create an invisibility cloak?  I mean if it was possible it would be insane.  But what if there exists a material that scientist created that allows it to bend light or an electromagnetic radiation of an object, giving the appearance that it isn’t there at all.  Light is electromagnetic radiation, made up of vibrations of electric and magnetic fields. Natural materials usually only affect the electric component.  However metamaterials can affect both the electric and magnetic field.

## Hovercraft

The hovercraft hovers by creating a cushion of air with enough pressure to the weight of the craft and the passenger.  The fan constantly blows air molecules into the cushion.  The cushion inflates, and there are a couple of holes in the cushion that allows some air molecules to escape so the cushion doesn't explode from the pressure.  The trick to get the craft to hover is to have the air molecules exert greater pressure or force than the weight of the craft.  The air pressure needed to lift th

## Time Travel

Is time travelling even possible? Maybe, but to time travel a person has to be faster then light which is impossible because no one has enough energy to move faster than that speed.  However, Einstein’s special theory of relativity, developed in 1905, shows that time passes at different rates for people who are moving relative to one another - although the effect only becomes large when you get close to the speed of light.  If anyone has seen the TV show, the "Flash," the Flash is able to run at

## Airplanes

The last time I was on a airplane was when I was traveling to Florida for vacation.  I wondered how almost 200 people and the mass of the plane didn't weigh the plane down.  The forces on the airplane is at equilibrium when the airplane reaches at a certain altitude.  Additional when the airplane reaches at a constant velocity therefore the forces on it all must be balanced.  This means that the lift force (L) generated by the airplane wings must equal the airplane weight (W), and the thrust for

## Dancing

Both of my sisters used to dance and when I was younger I went to their dance recitals.  Every year I went, there was always that one dancer who would spin on her toe for the longest time.  I always notice that when ever the dancer slowed down while spinning, she whipped her legs around in a circle again and then she started to spin faster.  I have always wondered how one leg motion could keep you spinning for the longest time.  Well this simple spinning of a dance can be explained through angul

## Music

Music, who doesn't like music?  Music is an universal langue. Music can be heard in any mood or activity.  It's just a thing that everyone does.  Yet how can we listen to music in general? Well sound is produced when a medium is being vibrated.  A medium could be air, water, etc... Vibrations in air are called traveling longitudinal waves, which we can hear.  The reason why sounds can't be heard in space because there is no medium where sounds can vibrate in.  Since sound can't vibrate in a medi

## Eyes

I have horrible eye sight, so that's why I need glasses to see better.  And yet I never really understood how a mirror could make you see better.  Until last year, when we learned in physics of optical glasses.  Our eyes are concave, and the distance between our cornea to our retina is the focal length.  So the light that hits our eyes allows us to see images.  People who have twenty/twenty visions have eyes that aren't small or elongated and the focus is at the retina.  This allows people to se

## High Jumping

Watching the summer Olympics last year was really intriguing because of the High Jump.  I have always wonder how someone with just a pole could jump so high above a bar.  Now I know there's physics behind it.  First of all, before the person jumps above the bar, the person with pole has  to generate speed to the high bar.  This speed generate before the person jump increases the kinetic energy of the person.  Then the person plants the pole down at an angle and jumps, the person is then able to

## Explosions

It's hard to think about a how an explosion has momentum conserved because an explosions blows up everything in little pieces.  However, those infinite amount of pieces all contribute to conserve the momentum of the explosion before it exploded.  The law of conservation has a simple equation of mass times velocity initially equals the mass times velocity final.  An explosion before it happens is equal to zero because it has no velocity at all.  After the explosions, the pieces broken off in the

## Roller Coaster

Roller Coasters, how do they move so fast without any motor pushing them? Energy!  More specifically kinetic and potential energy.  In the beginning of a roller coaster ride, there is an ascension to the top of hill.  The purpose of this is that as the roller coaster gets higher and higher up, it gains potential energy.  You could calculate this by doing mass times gravity times height.  After the the roller coaster reaches to the top and starts fall down, the potential energy is then transferre

## Sledding

Sledding, a fun activity to do over the winter, applies to Newtons laws of motion.  Newton's First Law of Motion, the Law of Inertia, states that an object will not change unless it is acted on by an outside force. This means that an object at rest will stay at rest until a force causes it to move. Additionally, an object in motion will stay in motion until a force stops it.  When you are on top of a hill, there is no force pushing on you therefore you don't move. When you go down the hill, the

## Wi-fi

What is wi-fi? I used it all the time, but never really knew what it was. Wi-fi uses radio waves and sends out these waves to different devices to give them the power of the internet.  They send out around 2.2GHz - 2.4 GHz, These waves have similar frequencies as mircowaves.  These waves travel through the air, undetectable by the blind eye and they send out "information" to other devices.  The reason why people lose connection to their wi-fi after traveling some distance is that waves can only

## Washing Machine

Ten months from now, I have to do my own wash, so my parents are making me practice now.  Anyways, while I was doing my wash, I realized there is physics behind the washing machine rotating the the clothes around.  I realized that someone could calculate the centripetal force of the machine.  A person would have to mass the washing machine, then a person would have to measure the radius of the machine.  Then to find the velocity of you would use kinematics.  First you know the amount of time of

## Cello

Cello, the best string instrument, creates beautiful music.  But how does a cello create sound?  Well, sound is produced by the vibrations of the string, and these sounds resonate inside the cello.  Cello strings are fifths (five notes apart) and each string creates their own frequency when you place your finger down on different parts of the string.  As you place your finger down the fingerboard to the bridge of the cello, it creates a higher frequency.  As you place your fingers up the fingerb

## Laser Surgery

Apparently, I have a mole that has a small chance to become cancerous, so I have to undergo laser surgery to get rid of the mole.  That lead to me to think, how is it possible that a laser could remove skin off a person's body, without hurting the surrounding skin.  So I learned that LASER is an acronym the represents Light Amplification by the Stimulated Emission of Radiation. So basically, lasers emit monochromatic (single color/wavelength) light that are designed to send ultra-pulses of light

## Breaking a Board

I used to practice martial arts and one day in our dojo, my sensei decided that we should have fun by breaking boards.  Although breaking a board seems impossible for a person who doesn't do martial arts, it is quite simple if we look at the physics of breaking a board.  For example, a person needs to generate a certain velocity to impact the board at a certain position.  A person should make the impact/position of where your hands end, up past the board.  Otherwise your hand will have a tendenc

## Hockey Shots

Shooting a puck, wrist or slap shot, requires a player, using their stick to apply a force greater than the frictional forces(very little, due to ice being relatively smooth) resisting the puck's movement.  Players have the ability to generate lift because all stick blades have a certain "tilt" angle.(the face of the blade is turned slightly upwards).  During the shot, the puck slides along the face of the blade and it is the tilt which allows it to be lifted off the ice surface.  Players who ge

## Firing a Gun

Recently I was watching Point of Interest, a TV show, and I was thinking about what kind of physics are behind firing a gun.  I concluded that when the shooter shoots a gun, the force on the bullet is equal to that on the gun-shooter. This is due to Newton's third law of motion (for every action, there is an equal and opposite reaction).  The force of the bullet is equal to the gun-shooter due to the law of conservation of momentum.  A person with a gun have a combined mass M and the bullet has

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