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Showing content with the highest reputation on 04/18/2013 in all areas

  1. 1 point
    there has been a large amount of misconception around this topic, a major contributor being the fact that people mix cornstarch and water and call it a non-newtonian fluid, when in fact it is only a colloid. colloids are not fluids, as they are heterogeneous, consisting of liquid and fine particle mix. they have changing viscosity because the particles cant flow away as fast as the liquid, and are bunched together as a pseudo solid. this is different from a non newtonian fluid because the fluid changes viscosity because it is in a near-crystalline state, and acts like a crystalline solid as pressure is applied. some examples of this are jolly ranchers(corn starch), some types of bullet proof glass, and shampoo
  2. 1 point
    i have a problem. every time i pick up a cat to let it fall to its death, it manages to turn around mid air and land square on its feet, even when im not giving it any initial rotational speed. the law of conservation of angular momentum says that the cat can not start rotating after i have dropped it, assuming it starts with no angular momentum at all. so how they do it? turns out, they actually bend themselves into a v shape in mid air, breaking their rotational axis in two. this lets them turn their front half against their bottom half via muscles in their torso, resulting in both rotational motion along the center of mass, and along each side of the v they created with their body. this allows them to quickly spin around while still conserving their total angular momentum. when theyve turned 180 degrees, the cat simply bends out from the v shape, into what is more or less a line, in which state the cats is not turning at all, because the net angular momentum must be zero, conserved from the beginning. therefore, cats are immortal.
  3. 1 point
    yesterday i opened the window in my room because it was particularly warm outside, and throughout the day as i entered and left my room, i would accidently slam my door, even though i was accelerating it to the same speed to close it as i usually do. as i got used to my now much easier to close door, i thought about possible explainations for this annoying phenomenon. i hypothesized that the culprit was my open window. i figured that when the window was closed, the shutting of my door was harder because while shutting, i was doing work not only on the door, but also on the gasses inside my room because the door acted like a plunger, increasing the volume of my room faster than air could enter and decreasing the pressure inside. with my window open, gas can come in both through the window and through the crack under the door, increasing the speed at which air could enter, therefore decreasing the difference between the rate of incoming air and the rate of increasing volume. with this difference smaller, the door does less work on the air inside because it doesnt need to decrease the pressure to close. with the window closed, i was used to giving more speed to the door to close it, but now that the window is open and less of the energy i give the door is used to change pressure, the speed i usually use is too much, and the door slams.
  4. 1 point
    usually, when shot at, the average person would have neither the reaction time, nor the hair strength to deflect a bullet with a braid of his hair. the mere thought of such an impulse delivered to a bullet without crushing it or harming the hair seems to go against all physics, however for those of you who have seen the movie pootie tang, starring pootie tang, you know that pootie dont need no words, pootie dont need no music, and apparently pootie dont need no physics. https://www.youtube.com/watch?v=9F8ahCk_qhY
  5. 1 point
    one very dull free period today i was wondering if Mr. Fullerton had not gone into physics, what would be his profession? i found prison-hardened hardcore gangster rap artist to be the most probable of options.
  6. 1 point
    last year with Mr. Powlin we made some simple water bottle rockets after the ap exam. as we designed and built, we had a basic understading of what our rockets were supposed to look like, but for the most part were in the dark as far as the technical physics behind it. this is what i hope to explain. the common expression "this isnt rocket science" may have you expecting long equations with foreign symbols, however simple rocketry in its essence is counterintuitively pretty simple. for the type of rockets we made last year, only one condition is required for it to maintain its orientation, being that the center of mass must be higher on the rocket than the center of drag. This is why Mr. Powlin kept telling us its better to have more weight at the tip, the farthest point ahead of the center of drag, the fins. keep in mind that this only accounts for the meathod of stabilization using friction, as there are other ways to keep a projectile oriented, such as the use of gyroscopic forces, as used in bullets. PS, if you want to calculate more complicated aspects of rocketry, you will run into some pretty nasty equations.
  7. 1 point
    if you were to ask an average physics student about graphene, he would probably tell you about its potential to be used for its structural properties, more specifically its unsurpassed strength to thickness ratio. However, graphene also has many unique and desireable electrical traits. Because graphene is extremely thin, relatively strong, and conductive, you can use sheets of it as plates for a capacitor. the advantageous thing about a graphene capacitor is that you can fit a lot of plate surface area into a small space, giving the capacitor a much higher energy density than conventional batteries. With this technology inside a common electronic device such as an ipod, for the same storage space one could theoretically charge it to full capacity in as little as three seconds, the charge lasting several weeks. although this technology is still far off, one can imagine how mch it would change our lives.
  8. 1 point
    so the other day i let my rabbit have free range of my room for a few hours as i was doing my webassign, and after a while the mouse i was using for my computer stopped working. i checked the plug, and to my confusion it was still plugged in. as i attempted to diagnose the problem i looked below my desk for a moment, finding my rabbit with a mouthful of copper and plastic. tasty. unfortunately he had not only chewed through my mouse cable, but also that of my webcam, among others. i got out my soldering iron and strippers, and as i removed the insulating tubing from each wire i found something interesting. on the mouse wire i removed the insulation to find only the four wires typical of a usb cord, however as i peeled back the insulation on the webcam wire, there was a second layer of braided wire and foil around the center four wires. at first i thought this may be an other data-carrying wire, or possibly a ground, which wouldnt make sense since usb uses very low voltage. i then realized it was just a conducting shell there to block interference with the webcams image quality from outside radio noise using the faraday cage effect. i hypothesized that my mouse didnt have this extra layer because the location of a mouse pointer is somewhat arbitrary on the small scale, so blocking this small ammount of interference would not be cost effective for the company that made it. moral of the story: faraday cages can be pretty useful.
  9. 1 point
    due to my procrastinativity, i now have to due all ten posts in one night. its getting quite bland. i feel like talking about computer screens, as it is what i have been staring at for the last hour. so i shall. most screens are lcd, or liquid crystal display. i dont really know why crystals are involved, but it makes me sound like i know what im talking about. in an lcd screen, there are hundreds and sometimes thousands of small boxes called pixels that make up an image. Typically, each pixel is composed of three sections, each for one of three of the primary colors. as you probably know, the primary colors are all you need to make any color out there, however there are two different sets of primary colors, to be used with different applications. why? one set is the additive primarys and the other is the subtractive primarys. in second grade art class, the primary colors were red, blue, and yellow; the subtractive primarys. these were used because paints and inks and such use subtractive color blending, meaning they absorb, or subtract out some wavelengths of light that hit them, the rest reflecting into your eyes as a specific color. each color subtracts a different wavelength from the original white and reflects only one wavelength, and by blending them you can subtract just the right amount of each from white for your desired color. for computer screens, however, (also projectors, ipods, anything that emits light to create colors), the additive primaries are used, being red, blue, and green, one for each section of pixel in an lcd screen. these are different because with a pixel, colors are created additively, or shining just the right ammount of each wavelength from the different color sections, adding just the right ammount of each for your intended color. for example, you see yellow on a screen because red and green light is hitting your retina, activating some green receptors and some red receptors, which your brain recognises as yellow because it is close to the middle of these two wavelengths. also, white light can only be made with additive primaries, as you add all the wavelengths while black light can only be made by subtractive primaries, when you subtract all the wavelenghts from the original white. doesnt this mean computer screens cant create black? they do so by not adding any color, relying on the background of the screen to absorb light that hits it, so actually, every pixel displaying this text is actually every pixel thats not displaying this text. mind. blown.
  10. 1 point
    This being my first blog post, i feel obligated to comply with the requests of Mr. Fullerton, and share with my loyal readers some things about myself and my outlook toward physics c. To describe my background, i would say that i have a wide range of interests, a large portion of which are science related, including microelectronics, circuitry, optics, botany, and laser physics, and a small amount of computer sciences, though i am not very good at it. the main reason i am taking physics c is because my brother tells me calculus is helpful for things, and simply because i am fond of the subject. last year, Mr. Powlin told us that c is more focused on electricity and magnetism than b, which is something i would like to learn more about. the bulk of my anxiety for this class stems from the fact that there is a lot of work to be done, something i am not looking forward to. overall, i think this year will be a valuable experience. thus concludes my first transmission.


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