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Everything posted by pavelow

  1. pavelow

    Two-way mirrors

    "I'll take mirrors for $200, Alex." "This type of mirror is a mirror on one side and a window on the other." "What is a one way mirror?" "You got it."
  2. Light is subject to a quantum theory called wave-particle duality. This theory proposes that matter exhibits both properties of a particle and properties of a wave. The experiment that shows light's wave-like properties is the double slit experiment. when light was shone through two slits close together, and a screen was placed behind the slits, the impact pattern didn't look the way one would expect a particle impact pattern to look like. After going though the slits, the light diffracted, creating a wave diffraction pattern on the screen, showing light's wave-like properties. Light's p
  3. A military application of electromagnetic force is the rail gun. A rail gun is like a regular gun in the sense that it fires a projectile out of a barrel, but it has some major differences. A regular gunpowder gun uses a projectile with a firing pin, which is hit by the gun, pressurizing gunpowder, resulting in an explosion which propels the projectile forward. This is a bit inefficient however, because a lot of recoil occurs in the gun because of conservation of momentum, and a lot of excess heat is produced. The rail gun propels the projectile differently. Instead of using gunpowder
  4. Magnetic Levitation (Maglev) trains are one of the ways electromagnets are used every day. Maglev trains carry passengers at speeds of 310 mph. The trains are able to reach such high speeds without falling apart partially because of their sturdy design but also because of their propulsion system. The trains are held up by magnetic forces when they approach higher speeds.the lack of physical contact with rails reduces friction to only that of air resistance, allowing the train to be more stable at high speeds. The main issue keeping maglev trains from becoming more common is economic
  5. The electrical grid is wired in parallel. Why? The benefit of having your home wired in parallel rather than in series is having a uniform voltage rather than a uniform current. Because your home is wired in parallel, manufacturers of electrical products can set a specific resistance and know the expected current because of ohm's law V=IR, rearranged to I=V/R. The danger of having everything wired in parallel is that increasing the amount of resistors in the circuit decreases the equivalent resistance of the entire circuit. This can lead to a dangerous amount of current travelling tho
  6. "The ocean covers 71 percent of the Earth's surface and contains 97 percent of the planet's water, yet more than 95 percent of the underwater world remains unexplored." Source: http://www.noaa.gov/ocean.html Many obstacles exist keeping widespread ocean exploration from becoming something not extremely difficult. One obstacle is the pressure under water. "The deeper you go under the sea, the greater the pressure of the water pushing down on you. For every 33 feet (10.06 meters) you go down, the pressure increases by 14.5 psi (1 bar)." Source: http://oceanservice.noaa.gov/facts/p
  7. An electromagnet is created when an electric current produces a magnetic field. Electromagnets have multiple applications and are a popular application of magnets. Electromagnets are often used in large metal scrapyards where large amounts of metals need to be distributed quickly and efficiently. A crane with an electromagnet on its arm is perfect for this task because the crane operator can induce a current to magnetize the electromagnet and pick up metal, and then cut the current when he wants to release the metal from the arm. Scientists often use electromagnets for experiments be
  8. Substances are magnetized when their electrons spin in the same direction. What this does is it creates charge differences in a substance. Magnets have north and south poles. These poles dictate the direction in which the magnetic field flows both inside and outside of a magnet. On the outside, field lines flow north to south; inside they flow south to north. Interestingly enough, magnets will always have both a north and a south pole. This can be observed if a magnet is cut in half. Since the poles are the result of the flow of field lines, and the field lines always form loops, there c
  9. There are two often used ways of avoiding RADAR (RAdio Detection And Ranging): Stealth and Jamming. My previous blog post covered stealth. This one will cover jamming. World War Two era planes weren't equipped with stealth technology to avoid radar, because it didn't exist yet. The air forces of the world had to figure out ways to avoid radar, and thus they figured out how to jam radar. World War Two era bombers were easily picked up by radar, so to confuse the towers, the planes released aluminum chaff. From the tower's point of view, all the signals from the chaff looked the same as
  10. There are two often used ways of avoiding RADAR (RAdio Detection And Ranging): Stealth and Jamming. This blog post will cover stealth. Radar can be rendered useless or less useful if the radio waves sent out by radio towers never return to the towers themselves. Airplanes today are equipped with more than one way to hide from radar. One way planes can avoid sending radio waves back to towers is by only allowing radio waves to reflect at one angle. The B2 bomber, as shown in the picture, was engineered to be as flat as possible, this causes radar waves to bounce off the plane as
  11. Radar is used by militaries and civilians of the world for object detection. Radar works when a tower shoots a "beam" of radio waves in a direction. If an object is in this "beam" of radio waves, the waves will bounce back to the tower. The owner of the radar tower receives two very important types of data from the use of radar: Distance and velocity. Distance between the radar tower and object is determined by the time it takes the radio waves to return to the tower after they are initially shot. The radio waves travel at light speed. Therefore, it's pretty easy to determine the dist
  12. Every teenager has stayed up late, woken up early, regretted their decision, end then slept extra long the next night. Can a person really catch up on sleep? Numerous studies have been conducted on the subject, and what is the prevailing hypothesis is that there are two systems dealing with sleep, a circadian process and a sleep homeostatic process. The circadian process is a rhythm of sleepiness and alertness over a twenty four hour period. This clock is related to the amount of light received by the eyes and can change when stimulus to the eyes is removed. This cycle is controlled b
  13. When cars get into a collision, why does it seem like half the car gets turned into debris? The answer is simple, conservation of momentum. In elastic collisions, like car crashes, the projectiles have a lot of momentum. If a head on collision occurred where the cars stayed perfectly rigid, the occupants would have a huge change in momentum. This used to happen before modern safety regulations. Modern cars are designed to "give", absorbing a large amount of momentum and keeping the occupants from experiencing the same change in momentum, saving lives and livelihoods in the process. It
  14. Melting/Freezing points and Boiling/Condensing points aren't just based on temperature; pressure is also involved. This fact can be observed by having a weighted wire go through a block of ice, as witnessed in this video. As shown in the video, pressure is also a major factor in determining the melting point of ice. On a molecular level, the molecules under the wire get increased kinetic energy, causing them to become liquid. once the wire passes through that part of the block of ice, the molecules lose the excess energy and refreeze. The melting/refreezing phenomenon also happens w
  15. There are two types of nuclear reactions that are very prevalent in today's society: fission and fusion. What are these reactions and how are they used? Nuclear fission is a reaction where a molecule splits into smaller molecules and excess subatomic particles, and releases energy. This type of reaction happens in nuclear bombs and in nuclear power plants. In nuclear bombs, this reaction is set off by a neutron hitting a nucleus, making it unstable and causing fission. In a bomb, this happens in the vicinity of an amount of a particle, called critical mass, where the reaction becomes a c
  16. The calculation for escape velocity is a pretty simple conservation of energy problem. K at infinity =.5mv2 = 0 because v at infinity = 0 U at infinity = GMm/r = 0 at infinity because r = infinity K=0 U=0 K=U .5mv2 = GMm/r From there it's simple algebra, and escape velocity is ve = sqrt(2GM/r) This equation's applications are seen in the exploration of space. Spacecraft need to reach escape velocity in order to not eventually crash back into the earth's surface. Some satellites are orbiting earth at just above escape velocity, meaning that they are actually spiraling away from th
  17. This blog was inspired by this fact: The New York City water supply system leaks at a rate of up to 36 million US gallons (140,000 m^3) per day. Source: http://www.nytimes.com/2008/11/23/nyregion/23tunnel.html?pagewanted=2&_r=0 Our water is extensively purified, and is completely safe to drink, but how can it be safe if some of the biggest supply pipes have holes all over? Besides the full -on sanitation of the water, one part of the solution is that our water supply contains some residual chlorine and other chemicals that stop bacteria growth from occurring in tap water. Any pip
  18. Is it just me or does it get quieter outside when a couple of inches of snow are falling? Actually, the answer is a combination of both. First of all, during a big snowfall, there are likely to be less people and other noise making devices outside, so there is less initial sound hitting they eardrums, without regard to any effect the snow has on sound waves. What if the amount of noise made is the same before a snowfall and during/after? Sound waves are absorbed by porous and insulating materials. Freshly fallen snow has plenty of air pockets for sound waves to get trapped in. Regu
  19. What is Pavel time? Pavel time is the time right before a deadline when actual work gets done. How does this relate to physics? It relates specifically to Albert Einstein's theory of relativity. Part of the theory of relativity states that measurements of various quantities are relative to the velocities of observers. In particular, space and time can dilate. So, in real life, as an object approaches the speed of light, it gets squished and time slows down for the object. How does this relate to Pavel time? In my theory of relativity, as more work gets done more quickly, time s
  20. Walking is just controlled falling. Don't believe me? Take a step. The human body has its center of mass high up off the ground, so it requires a continuously acting balance system. When you take a single step, you shift your weight forward in such a way that if you didn't have a balancing system, you would fall flat on your face. At the last second, you swing a leg forward and catch yourself, regaining your balance. Taking a walk is just repeating the same motion over and over again. The reason walking is not thought of very often throughout the day is because it is intuitive. It is
  21. The Nimitz class aircraft carriers currently in service for the US Navy weigh anywhere from 102,000 to 106,000 metric tons. If these gigantic ships weigh so much, why don't they sink? The way a ship floats is not only dependent on its weight. Even though the ship is extemely heavy, it displaces an amount of water which weighs the same amount as the ship. If more of the ship goes under, the weight of the water it would displace would be more than its own weight. This phenomenon causes the water to exert a buoyant force, counteracting the weight of the ship and allowing it to float.
  22. Torque is the tendency of force to rotate something around an axis. Torque helps you turn a doorknob, it makes a car's tires spin, it basically helps a force act in a circle. Applications of torque equations can help solve real world problems. Locations for supports for bridges can be determined by examining the effects of the torque vehicles would cause on a bridge. An engineer looking to efficiently maximize the potential for producing torque in an engine would choose electrical or diesel power over gasoline power to use the fuel effectively. People who would like to easily compare
  23. Veritasium, a channel on YouTube, posted a series of videos showing an experiment where a bullets are shot into blocks, where one time, the bullet is shot into the center of the block, while another time, the bullet is shot off-center. The first video can be watched here: And the second here: The explanation for the result of the experiment has to do with momentum. While the second block has more energy, it has the same momentum as before, because linear and angular momentum are independent of one another. Because kinetic energy is not conserved in inelastic collisions, the syst
  24. What? Gravity is weak? Then how am I not floating right now? This has to be a joke. It's not. Gravity is one of the four fundamental forces in our universe. The others are electromagnetic, strong nuclear, and weak nuclear forces. Gravity is the oddball in this group. It is also preventing the completion of the unification equation. While the other forces, besides E-M, have relatively short ranges, gravity does not. Gravity has infinite range, and has a bigger effect over range than other forces. Gravity is pulling the Milky Way and Andromeda galaxies together at this very moment. G
  25. In our body, we often consciously use our skeletal muscles. Our nervous system sends an electrical signal to our muscles which affects proteins which cause our muscle to contract. Electrical energy is transmitted which begins a process of chemical energy being converted to mechanical energy. Some smooth muscles behave like skeletal muscles, while others have contractions which are regularly and methodically induced by specific cells. The actions of these cells keep systems such as the digestive system working continuously without conscious thought. The heart, the cardiac muscle, is contr
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