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Momentumous

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  1. Momentumous
    1) The course is HARD-- and it doesn't get easier as you go along. The longer you wait, the harder it gets, and the more you'll have to do.

    2) Deterrence-- as this challenging work gets harder and harder, you're going to be less and less inclined to do it. Think about it, I'd be far more proactive about climbing a 5 foot cliff than a 100 foot cliff, if you do it in chunks it won't seem so bad.

    3) Imagination-block-- if you have ANYTHING creative to do (like blog posts for example), you're going to have to be full of ideas. If you have to sit there and think of 10 different things to talk about in one day rather than over 10 weeks, it's going to be a LOT harder to think of something.

    4) Cognitive function-- when a body is tired or stressed out, decreased cognitive function (you're ability to think at optimum levels) is a common side effect. Like I said, this course is HARD, you're going to want all the cognitive function you can get!

    5) The test date isn't changing-- due dates are the procrastinators worst enemy; and trust me, they don't move because you have a tradgic illness called procrastination. The AP exam is set and in May, regardless of whether you try to cram the stuff in the day before or months before.

    6) Memory retention-- repetition is your friend when you're trying to memorize something. If you don't leave yourself enough time to practice and repeat everything you need to memorize (and there's a LOT of that in any physics class), you're just not going to remember it. And it's pretty common knowledge you're not really going to remember what you crammed an hour ago--you're going to remember what you've practiced so many times it seems stupid to not remember.

    7) You work better in pieces-- alright maybe not literally in pieces, but work in small chunks is a good thing! By taking things in small portions, deterence lowers and cognitive function is at a higher level (wooo big words!) making it optimum to work as the work comes rather than saving it until right before it's due.

    8) The teacher knows what they're doing-- meaning if they give you lots of time to do something, it's PROBABLY because you actually need it. You can never really tell how long something is actually going to take you until you start it--which means you could pretty much s.o.l. if you save something till last minute

    9) Spontaneous fun--let's be real, NO ONE ever makes plans to do fun things anymore. Don't you want to be able to be spontaneous?! No one wants to say "No, I can't go {insert beloved task} because I have physics to do." Get it over with and open up time to enjoy a little spontenaity

    10) Because I said so; no better reason than that
  2. Momentumous
    With a little digging, I was able to figure out how transitions lenses really work on this website:
    http://en-us.transitions.com/Why-Transitions/The-Technology/Photocromic-tech/

    To sum it up, within the lenses are photochromic molecules. These molecules react to UV rays and actually change their structure when exposed, which is what causes the lens to darken.

    And some fundamentals of weather still play into effect. When it's hot, the lenses react more quickly because the heat allows molecules to move faster, which in turn means the photochromic molecules can change their shape more quickly. The reverse is also true for the cold, since molecules move more slowly in cold tempurtures, the lenses will react more slowly in cold temperatures as well.
  3. Momentumous

    Ice skating!

    By Momentumous,

    Ice skating has a lot of obvious physics involved.

    For one, you could easily look at the centripital motion invovled when a figure skater spins. Conservation of angular momentum plays a huge roll in how they control the speed of their spins, but we've all heard that before.

    There's physics involved in the very fundamental movement of iceskates. When you iceskate, you put a lot of pressure on a very small, thin surface area. This force, as well as the friction between the blade and the ice, actually causes the ice just beneath the skate to melt. So in actuality, you're not ice skating--you're water skating. This is why ice skating leaves tracks behind you; because you melted the ice in divets where you're skates were. The friction is also why you can glide to a stop pretty easily-- since there's enough friction to melt the ice, there's plenty of friction to slow the skates to a stop. If you didn't keep propeling yourself and adding force into the equation, you'd never go anywhere.
    Friction plays a HUGE roll in control during the winter!
  4. Momentumous
    1) As seen in the video, though normal tires won't be quite so flexible as the tires shown, tires flex QUITE a bit when you rev your car to a start. With a common knowledge of the fact that materials get harder in the cold, severe cold weather could pretty pheasably cause damage to the integrity of the material should you rev them too fast.

    2) The cold air not only makes the rubber more dense, but it makes the air inside the tires more dense as well. That means your tire pressure--should you be the more common not-so-diligent-pressure-inspector--is lower than it should be. This in and of itself causes the amount of surface area of the tire touching the ground to decrease, which will give you less traction to begin with. Traction is good during the winter

    3) By scrambling your tires as fast as they can go, you're causing QUITE a lot of friction, and even cave-men figured out the unavoidable side effect of such is heat. This heat often leads to the snow under the tire getting melted, meaning now you're trying to skid on a water-slush-ice-snow combo. Trust me, snow tires are made for SNOW, you're better off dealing with just that.

    4) It wastes gas! Seems a little obvious that gas is wasted when you're sitting there pedal to the floor but not moving, but whats more you're making your car work pretty hard to go nowhere. It's a bigger waste than you'd probably think, and not so nice for the environment either!
  5. Momentumous

    Transition lenses

    By Momentumous,

    We've all seen transition lenses before, but how do they work?

    This is purely theoretical on my part, I have no idea how they actually work. But my knowledge of physics leads me to some pretty plausible conclusions.

    We all know how excited electrons work, and a lot of things can happen as a result of the expended energy when these electrons return back to their normal place. Light particles can exude quite a bit of energy. If that energy can be harnessed to produce electricity, its pretty easy to see that it could be used to change the color of a lens. Clearly the transition bit has to do with the material the lenses are made out of. Perhaps this material has electrons that react in such a way that they turn black when excited, the brighter the light, the more electrons excited the darker they get. Or perhaps it's not the electrons and is simply the particles themselves within the material.

    If anyone could enlighten me as to how these REALLY work, I'd love to know!
  6. Momentumous

    Physics of skiing!

    By Momentumous,

    Yesterday I went skiing for the first time (and no, I did NOT look that cool). And somehow as I was going down the slopes (very VERY slowly with lots of falling involved), I realized there's a LOT more physics going on that one would think initially.
    For one, there's a LOT of friction problems. Obviously the goal of most skiers is minimal friction, and therefore go faster! However that was NOT my goal, considering speed led to panic which lead to crazy turns which lead to the unavoidable fall. So my goal was to maximize friction.
    The easiest way to do this is to make a wedge and to turn a lot--go across the slope at small angles rather than straight down. This helps for obvious reasons; with the wedge, the edge of your skiis dig into the snow more, causing more friction and removing some of the slick, waxed surface area from the low-friction snow. The turns are a little more complicated, considering you can go QUITE fast if you do them a certain way. However in a sense the concept of using turns to go slow is simple; the ground you cover when you go down a slope in wide turns is less than if you were to go straight down. Energy is expended on turning, and friction is increased by going more sideways (using more of the edge of the ski than the waxed bottom) rather than going strait down.

    There's a lot more physics involved when you look at moguls, jumps, and even the design of the skis themselves. However, considering I've only gone once, I'm going to leave an analysis of that up to the experts.



    Friendly ski tip to beginners: NEVER fall backwards downhill on your skis if you can avoid it, you will NOT stop going down the slope
  7. Momentumous

    Non newtonian fluid

    By Momentumous,

    Sadly I still can't figure out how to embed a video and more likely than not no one will watch it if its a URL so a picture will have to do!

    This odd goop is called non-newtonian fluid. A newtonian fluid has a stress vs strain curve that is linear and passes through the origin, showing it has a constant viscocity. With a non-netonian fluid, it follows no such rules, and it's viscocity can change depending on stress, strain, time, or all of the above.

    A simple example is this oobleck seen above. Its a simple 1-part water 2-parts cornstarch mixture. If you try to make it, eventually the stirring becomes suspiciously more difficult. This is because once it's thoroughly mixed, it is a non-newtonian fluid, and the stress caused by your stirring makes it become temporarily solid.

    Infact, this corn starch mixture becomes pretty easily stressed out. When you place the mixture on a subwoofer, the vibration from the sound waves are enough to stress it out, causing it to move and solidify in strange ways, as you can see in the picture above.

    Origionally I was going to make a video on how to do such, but I have no cornstarch and still need to figure out how inserting a video works, so perhaps another blog!
  8. Momentumous

    Physics Jokes

    By Momentumous,

    When a third grader was asked to cite Newton's first law, she said, "Bodies in motion remain in motion, and bodies at rest stay in bed unless their mothers call them to get up."

    Q: What is the name of the first electricity detective?
    A: Sherlock Ohms

    A neutron walked into a bar and asked, "How much for a drink?" The bartender replied, "For you, no charge."

    Have you heard that entropy isn't what it used to be?

    Q: How many theoretical physicists specializing in general relativity does it take to change a light bulb?
    A: Two. One to hold the bulb and one to rotate the universe.

    Does a radioactive cat have 18 half-lives?

    Q: What did Donald Duck say in his graduate physics class?
    A: Quark, quark, quark!
    :glee:




  9. Momentumous
    We've all seen a coffee mug that changes color when you put your warm coffee in it. Most certainly they're pretty cool looking, but I noticed they don't serve the primary job of a coffee mug--to hold your coffee and keep it warm as long as possible.

    At first I thought my coffee might have been going cold so quickly simply because the mug had a larger diameter than my others, making there more exposed surface area for the hot coffee to conduct heat to the cooler surroundings. However, I have a coffee mug that would expose even MORE surface area than my fancy color-changer, and it seems to keep heat even longer.

    So what's really going on here?

    Actually, once it hit me the concept is pretty simple. The only thing that makes the black background turn into vibrant colors on the mug is heat. So clearly that heat is what's being taken to produce the color change. Speculation makes me think it may be like exciting electrons--different excited electrons, when they jump back down to where they're supposed to be, emit different colors. But I have no idea what these mugs are made of and they aren't actually GLOWING, so it could be something entirely different. Whatever the case, it's quite clear that the appearance of the colors are stealing the heat from the coffee too appear. So on top of the normal heat loss to the surrounding atmosphere, the coffee is also losing heat to make the mug look pretty.

    A good bargain? I guess it depends on how fast you drink your coffee.
  10. Momentumous

    Wind turbines

    By Momentumous,

    Essentially wind turbines work to take the rotational energy of the turbine blades, and use a spinning shaft to convert that energy into electricity.

    The blades are curved unevenly to make a change in air pressure, which causes them to spin when wind hits them, just like an airplane wing. These blades are connected to a spinning shaft, which is connected to a series of gears that amp up the rpm's. This is connected to a generator, which translates the rotation into electrical energy.

    A generator works through electromagnetic induction. When a conductor is moving through a magnetic field, a voltage in induced through the conductor. The shaft and gears from the turbine are what move the conductors in the generator, which induce voltage and therefore generate electricity.

    The turbine seems complicated, but by concept, it's pretty easy. We all know that by hand making our tiny "engine" from wire coil magnets is pretty difficult. The generator is a larger scale concept, with the shaft spinning what would be the coil and, combined with the magnetic field, producing electricity. Not too bad.



  11. Momentumous

    Le Catapult

    By Momentumous,

    So lets face it, our catapult was awesome. Even if it didn't shoot 80 yards, the fact that we used garage door springs made up for it.

    But to the physics!

    Whilst reflecting on our design, I remembered that we had taken our current unit--impulse to be more specific--into account when making the catapult. We knew that the force from the springs would be pretty huge, make a pretty big velocity for the arm, so the stopper to make it launch at a 45 degree angle would feel some serious force, and so would the arm. With this in mind, we put a LOT of padding in the way (probably 20 ft worth of crib lining and a good, thick memory foam pillow). By adding the pillow, we decreased the force taken on the stopper as well as the arm.

    Just for kicks, we took off all the padding on our last launch. The result proves that the cushioning lead to an extra impact time, decreasing the impulse and therefore assisting the integrity of the arm and stopper; on the last launch, the arm shattered. Our slugger shall launch no more.
  12. Momentumous

    My internship!

    By Momentumous,

    I can't believe I didn't think of this as a subject earlier, I did LOTS of physics in my astronomical imaging internship!

    Okay, well, in reality I more looked at images and programs and readings, I didn't actually DO the physics, but there's a lot of physics behind what I did.

    My internship was focused on assisting with research around the stellar phase called planetary nebula. This is a post-red-giant phase of smaller stars. The majority of the gases within the star have been burned up or converted through fusion to different elements. In the planetary nebula phase, the outer layers of the star are now composed of ionized gasses, and the core becomes visible. Planetary nebula come in many different shapes, and the theories behind why they form some of the more obscure shapes is still hotly debated, though it is widely agree that interstellar winds create the basic shapes.

    I asked one day what an interstellar wind actually was, and received a lecture that resulted in this whiteboard:


    [ATTACH=CONFIG]529[/ATTACH]

    Mind you, many things have been erased and written over on this board to explain, and the lecture took at LEAST an hour as well as numerous pages of notes. So I will not be explaining interstellar winds, mostly because its a lengthy explanation and marginally because I don't remember most of it.

    The most relevant physics to what I was doing had to do with the ionized gases that surround the planetary nebula. As both basic chemistry and physics teaches us, excited atoms emit light. The gas surrounding the stars in the planetary nebular phase indeed emit a LOT of light, though often times this light is not emitted in the visible spectrum nor even in only one spectra. The emitted light comes in various wavelengths and therefore on various areas of the spectrum (visible, infrared, ultraviolet ect).

    To capture images of the emitted light with the most possible information, there are various telescopes and sattelites that take images on different levels of the spectrum (ie Galex sattelite takes xray images). Different spectral images are also useful because different levels of the spectrum correspond to different heats, which help astronomers figure out what is going on in the stars. With all of this in mind, astronomers can use wavelengths to figure out distances, numerous spectral images to deduce shapes, and emissions to figure out the temperature of things happening in space.

    Knowing that different things are emitted in numerous levels of the spectrum, my job was usually to gather images from different wavelengths to either see if there was any emission to begin with or to compare emissions we already knew were there. Physics plays a HUGE part in asrtronomy, since we have to use what we know to figure out things that we can do nothing more than observe from a great distance away. You can't exactly take a sample of a nebular gas (even if you found a way to handle the temperatures), so we have to use our knowledge of physics to figure out the mysteries of space.

    (the attached images are xray farthest left, and 3 different infrared wavelengths next to that)
    [ATTACH=CONFIG]525[/ATTACH][ATTACH=CONFIG]526[/ATTACH][ATTACH=CONFIG]527[/ATTACH][ATTACH=CONFIG]528[/ATTACH]
  13. Momentumous

    Spiderman's webs

    By Momentumous,

    Aside from the snazzy suit, you know who you're looking at is Spiderman as soon as stick webbing starts shooting from his hands.

    So if Spiderman does manage to shoot web through his spandexy-body-suit, this webbing must be seriously strong. For one, it can be shot through the air quick enough to go in relatively straight lines, and then miraculously latch on to some sort of object, and THEN can hold all of Spiderman's bulk!

    Spiderman is a hero, so he's probably around 5'10 and weighs 160 pounds (comprised mostly of muscle of course). This means that this webbing can can hold at LEAST 711.5 Newtons.

    But no, it can hold more than that!
    In one of the Spiderman movies, Spidey shoots out some webbing to catch a falling bus Presuming this is a smaller school bus, empty it weighs around 10,000 pounds. Considering the mixed crowd, its hard to say how much the people weigh, but lets say there were 50 people (comfortable seating) of each 100 pounds. That's another 5000 pounds, making the weight of the bus 15,000 pounds. So this webbing can actually hold up to a force of at LEAST 66678.22 N. That's pretty tough stuff!

    Oh, and spiderman can break it with a flick of his wrist. No big deal.
  14. Momentumous

    Bending a bullet?

    By Momentumous,

    Yes, this has indefinitely been proven impossible, but just how impossible?

    Google appears to have failed me for actual statistics on the infamous gun used in Wanted for the curved bullet, so lets just say this pistol has a muzzle velocity of 250 m/s (810 ft/s). Lets also say the barrel length is 5". So the bullet sits at rest with a velocity of 0 to 250 m/s over 5". That means in .000508 seconds (v=(x/t)=> x/v=t) the bullet got to the end of the barrel. Which also means it had an acceleration of about 500000 m/s^2 (a=(v/t)).

    With this in mind, note that you'd also have to have IMPECCABLE timing so that you change the motion of the muzzle JUST as the bullet is about to leave, nicking the bullet and therefore affecting its direction. So if you're so lucky as to have the timing down, you'd have .000508 seconds to move the muzzle.

    I don't know about you, but when I jerk my hand as fast as possible, I can still SEE the movement, it'd take some sort of crazy robot that can accelerate faster than 500000 m/s^2 to even hope to curve a bullet.
    Plausible? With modern technology, maybe, but certainly not by hand.

    (please note I know very little about guns from prior knowledge, these are theoretical values deduced from numbers I found online with some sort of frequency).
  15. Momentumous
    Hurricane Sandy has projected wind speeds that heighten at about 90 mph.


    So lets say some poor fool decides to go to the beach with this wind but not much rain, and stands observing 1 meter away from where the sand begins. It's pretty plausible that 90 mph winds could get a grain of sand moving, but how dangerous is that grain of sand?

    Well, lets say it takes the whole meter for the sand to get up to speed, and its final velocity is 90 mph just before it hits you. This is a velocity of 40.0 m/s. Using the equation (v)^2=(vo)^2=2ax, you find an accelleration of 808.02 m/(s)^2. If the grain of sand has a mass of .00000067 kg (.67 mg), then the net force felt by the grain of sand is .00054 N.
    The average muzzle velocity of a gun is 120 mph, only 30 mph (13 meters/s) faster. However, not only would a bullet's force be spread over a larger surface area, resulting in a lower pressure, but the force wouldn't be constant, since it would be slowed if only slightly by resistance. Whats more, a bullet lodges itself within a human, and "dangerous" is a standard that's reached WELL before deadly.

    So is a grain of sand dangerous? The grain of sand would generate a pressure of around .0119 psi. Considering the human body can withstand up to 50 psi on sudden impact, I'd say the sand isn't going to do anything traumatic. It might sting, especially if it gets in your eyes or throat, but it's certainly no bullet.
  16. Momentumous

    The physics of Heels

    By Momentumous,

    So lets say you're feeling crazy and want to wear some heels.

    Now you're about 135 pounds, the average weight of a female. That's approximately 61.2 kg. Multiply that by the constant of our friend gravity, and your body exerts a force of about 600N. Granted, this is split up between two feet unless you've had a tragic incident lately, so your foot feels about 300N of force just from standing.

    So lets look at it in terms of pressure, psi, pounds per square inch...or rather kg per square inch.
    Pressure is equivalent to F/A. If you're shoe size is a women's 8-9, your foot is probably around 10x3 inches. We'll shave off a handful of inches with the assumption that your foot is not perfectly rectangular, so lets say the area feeling the force of your weight is 25 inches.
    This means on a normal day with good arch support and nice, flat shoes, each foot feels a pressure of 12 kg/in^2. That's about 23 psi.

    So now you think, hey, let's wear some six inch heels!
    These heels are tall enough to essentially mean you're constantly standing on your toes. We'll attribute a square inch and a half for your arch "support" and heel, just for kicks, and what's left holding the majority of the force is the front pad of your foot and toes. That's about 8 square inches by my measurements. But the force exerted on your now 9.5 in^2 surface area hasn't changed. The force exerted on this surface area is still 300 N, and this area is less than half of the original surface area. 300/(9.5) is 31 kg/in^2 or 68 psi. That's almost triple the pressure your foot normally feels. That's like a full grown grizzly bear stepping on your toe.


    6 inch heels tonight? No thanks, I'll take my nike's.

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