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lindsh23

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Everything posted by lindsh23

  1. Hello friends! As I discussed in my last blog post, I have decided to take a look at the physics that goes on inside our very own bodies! This post will focus on the physics behind the movement of our bodies, mainly involving the muscular system. The muscular system works in close conjunction with the nervous system, which I looked at last time. Neurons transmit their impulses to the muscular system in order for the body to move in the way the brain intended it to. Muscles are made up of myofibrils, which are the smallest muscle fiber. Muscles are attached to the bone by tendons, and this attachment is what enables the muscles to move the bones of the body. When muscles contract, they create a force on the bone they are attached to, doing work in order to the control and move the bone the way the neurotransmission intended it to. Just like all objects in motion, the human body follows Newton's 2nd Law: the human body's rate of change of momentum is proportional to whatever force is applied to it: in this case, the muscles applying force on the bones. Since most body movement happens in the joints, which function as hinges and levers, much of the body's movement is angular movement. Torque is a property of anatomical movement often times investigated. Torque is often observed in the upper and lower parts of the arm surrounding the elbow, since it is such a common rotational joint: Joints act as machines which help the body to perform work more efficiently. Could you imagine walking around with absolutely no joints? A lot of motion would become incredibly difficult! Our joints act as levers by establishing a fulcrum point (again using the elbow as an example). The elbow itself is the fulcrum, and when a load is placed in the hand, the work done by the bicep is made significantly less than if done without the use of such a fulcrum point. Joints not only help with burdens placed by external loads... We can't forget what a heavy burden good ol' gravity can be on our bodies! Basically, without physics, humans would be completely bed ridden with no motion at all... which would make for quite the boring day. Even the human body has immense connections to physics! Until next time, Fizzix Community, until next time.
  2. I enjoy your face in the last picture but this is pretty clever for a blog post
  3. Since I spend so much time at New Visions and my future studies will most likely focus on the medical aspect of science, I have decided to see if I can create some blog posts focusing on the physics that goes on... in our very own bodies! Please excuse my nerdy anatomy obsession This post will focus on the physics behind our nervous system! Our nervous systems, both central and peripheral, focus on the idea of neurotransmission. Our nervous system relays messages from our body to our brain and back again using electrical impulses; this process is known as neurotransmission. Nerves near the surfaces of our bodies pick up stimuli from the environment, such as heat, light, and sound, via receptors. These stimuli cause the chain reaction of neurotransmission to occur. Here is a diagram of a typical neuron, or nerve cell: So what happens after a neuron senses a stimulus? Well, first, let's look at how neurotransmission is performed. At rest, the axon, or the shaft looking thingie, of the neuron is polarized. The outside of the axon contains positive sodium ions, and the inside contains positive potassium ions and negative chloride ions (I know, this seems like chemistry... but chemistry is basically the physics of electrons, so stay with me!). The fluid on the inside is negatively charged, giving it a negative potential of -50 mV. At rest, sodium ions cannot penetrate the axon barrier. A small electrical change caused by a stimuli causes the resting potential to become less negative, and once it breaks a threshold, it becomes permeable to the sodium ions, causing an action potential, where the axon fluid depolarizes. During this depolarization, sodium ions move down a concentration gradient, transmitting an electrical impulse across the neuron to the next neuron, triggering this action potential from neuron to neuron. While a neuron repolarizes (its way of regrouping), it goes through a refractory period, which is the delay between when it can fire its next impulse. This refractory delay prevents nervous system overload (what I picture as some sort of spontaneous nervous combustion!). The speed of neurotransmission is affected by the diameter of the axon (larger diameter=faster transmission time... more area for 'flow') and also by the amount of myelin sheath, or the insulation of the axon of the neuron. The deterioration of myelin is what causes multiple sclerosis, which is why those affected by MS suffer from the deterioration of their nervous function. Well, fizzix friends, I hope I have not bored you too much with my nervous system lecture. More to come on the physics of our bodies! Until next time, Fizzix Community, until next time.
  4. As I was watching Harry Potter, the cloak of invisibility reminded me of something someone in my New Vision's class brought up about the University of Rochester's own cloaking device. I decided to look further into the physics behind it. A cloaking device works by transmitting light rays around an object so that it appears as if nothing is there. The transmitted light waves, in theory, should look as if there is no background interruption. John Howell, physics professor at the U of R, and graduate student Joseph Choi created a cloaking system with minimal distortion of surroundings. It utilizes four different lenses, 2 with one focal length and 2 with another (the U of R did a lot of research on the specific focal lengths of these lenses to prevent distortion, I'm not positive on the ratios). The lenses are arranged F1 F2 F2 F1, and the lenses are then separated so that t1=F1+F2 and t2=2F2(F1+F2)/(F1-F2) (See diagram). The University of Rochester's cloaking device solves previous problems of cloaking in multiple dimensions. Previous cloaking devices worked successfully when the viewer was looking head on, but once their angle changed, the background was distorted, and it was immediately apparent that there was an object being cloaked. This use of light distortion and lensing may not be the cloak of invisibility Potter fans are familiar with, but I think any physics dealing with 'invisibility' is pretty nifty! Until next time, Fizzix Community, until next time.
  5. Remember that time our catapult for AP Physics C worked really well... yeah, me neither. So, the original design was beautiful, modelled to be a trebuchet. The idea is that once a counter weight is dropped at one end of the trebuchet, it causes the launching arm to move in circular motion and launch the projectile out of a sling, of which one end is released by the circular motion of the arm. While we did an excellent job building a frame for the trebuchet (mostly Justin, since I am absolutely not skilled with power tools and saws), our major issues surrounded the construction of the sling: it's shape, the angle of release for the free end of the sling, etc. We started with using a draw string backpack for the sling, but it held the softball too tightly, not allowing for it to be released at all. Then we took the netting of a lacrosse stick head and used that, and while it held the ball nicely, our fatal flaw came with the angle of release. The softball was often released too early, making it launch backwards (an issue which caused the need for a 'fore!' during an launches). What we really needed to do was spend more time testing launches to tweak the sling and find the prime angle that would launch it the furthest. The angle of the sling pin is one of the major factors which determines it's time of release. The more angled the sling pin is, the longer the sling stays attached to the trebuchet, and the longer before the softball is released. We should have messed with the sling pin more to find the best time for release. To be honest, if I had another chance, I would say let's just do a regular catapult. A trebuchet is great idea on paper...but since we didn't have the time and means necessary to do a quality job putting it together... a regular catapult would have sufficed. At least we had something to launch that day! And we did get some negative displacement Until next time, Fizzix Community, until next time.
  6. I love physics! After AP-B, I couldn't get enough. I even want to have a double major with one of my majors being physics. My love for physics has even drawn me to this big undertaking... The task of tackling AP-C by myself. Or rather, with the help of my teacher and the wonderful world-wide web. You see, I was not about to let some scheduling issues get in the way of AP-C; therefore, independent study was my destiny. I'm taking AP-C because I simply could not resist another year of physics before college. I am hoping to get a deeper background in Physics from this year, to better prepare me for my future studies in physics. I am really excited that I have the opportunity to take on such an endeavor, the same thing which also frightens me. But I have faith in myself, I just have to keep on top of things. Further updates to come about my senior year experiment! Only 8 more months until the AP exam
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