I have researched Newton's 3 laws of motion, but I do not understand what they have to do with a headrest in a vehicle and preventing injuries from whiplash. Please help to explain this to me!What is the role of a headrest in preventing injuries from whiplash, using Newton's 3 laws of motion?Then you don't understand the physics.
Actually all three laws can be lumped into one physics characteristic... the change in momentum, dP, which is called impulse. Here's how.
Impulse is dP = m dV = F dt; where m is your head as you sit in the car seat, dV = V1 - V0 is the change in speed of your body as your car gets rear ended with a force F for an impact interval dt seconds. V0 is your head and body moving along at, say, 44 fps (30 mph), as you drive through a residential area. V1 is the new, faster speed V1 %26gt; V0 because your car gets pushed from behind with that force F.
Now here's the deal. Your head is up in the air while your body is snug against the seat pan and back when you get rear ended. So your head, when the crash occurs, wants to continue on at V0 (Newton's First) while your body is pushed faster to V1 (Newton's Second). What happens? Your head slams backward (actually it's your car slamming forward, but it's all realtive).
If there is nothing behind your head (i.e., no headrest), there is nothing to stop it from slamming backward except your neck muscles and bones. Whiplash as your bones are cracked and your muscles are strained while stopping your head from flying off your shoulders.
But with that headrest, your backward flying head is cushioned upon impact and brought to a stop so that the backward force is offset by the reaction force of the headrest. And there you have balanced equal but opposite forces on your head while you try to get the car under control and brought to a stop (Newton's Third).
And there you are... all three laws, using impulse as the central theme and the physics.
Thursday, February 2, 2012
Can someone tell me if a slinky is a reciprocating or oscillating motion?
Also examples of oscillating motion, but please don't say pendulums or swings. Also is a seesaw oscillating?Can someone tell me if a slinky is a reciprocating or oscillating motion?It oscillates if it changes directions between two points repeatedly. Makes no difference what "it" is. If it moves back and forth, side to side, up and down, counter CW and clock wise, nose up and nose down, and/or roll left and roll right repeatedly, it's oscillating in one or more degrees of freedom (there are six degrees). The oscillations can be periodic or aperiodic or, similarly, regular or irregular.
As the teeter totter moves repeatedly nose up/nose down, that's its oscillation. I won't mention the p***s or s***s, but they oscillate nose up nose down as well (i.e., in the vertical plane around an axis of rotation).
A slinky can oscillate if you do it right. For example, if you hold it by one end and move it up and down, the coil will oscillate longitudinally along the length of the coil. In which case, the "two points" are the two ends of the coil.
But in other cases, by definition, it is not oscillating. For example, as it walks down the steps, it repeats the up, over, and down motion to walk its way downward. In other words, once I've defined one cycle, all the other cycles will be similar over time. But each cycle is between different points, different stairs as it descends. In which case, that is cyclical, but not oscillation by definition.
The pistons in a car engine also oscillate: they move up and down repeatedly between the top and bottom of their respective cylinders, their two points. But in that special case, they are claimed to be reciprocating; thus the name reciprocating engine.Can someone tell me if a slinky is a reciprocating or oscillating motion?Reciprocating is a saw motion i.e forward and back, open and close, slinky.
As the teeter totter moves repeatedly nose up/nose down, that's its oscillation. I won't mention the p***s or s***s, but they oscillate nose up nose down as well (i.e., in the vertical plane around an axis of rotation).
A slinky can oscillate if you do it right. For example, if you hold it by one end and move it up and down, the coil will oscillate longitudinally along the length of the coil. In which case, the "two points" are the two ends of the coil.
But in other cases, by definition, it is not oscillating. For example, as it walks down the steps, it repeats the up, over, and down motion to walk its way downward. In other words, once I've defined one cycle, all the other cycles will be similar over time. But each cycle is between different points, different stairs as it descends. In which case, that is cyclical, but not oscillation by definition.
The pistons in a car engine also oscillate: they move up and down repeatedly between the top and bottom of their respective cylinders, their two points. But in that special case, they are claimed to be reciprocating; thus the name reciprocating engine.Can someone tell me if a slinky is a reciprocating or oscillating motion?Reciprocating is a saw motion i.e forward and back, open and close, slinky.
How do I make stop motion videos?
I want to make a lyric video for Youtube with note cards and stuff, using stop motion. And I have NO idea how to. Any tips?How do I make stop motion videos?I did a stop motion video here:
http://www.youtube.com/watch?v=r7peBLoE2uc
To achieve this video I used my digital camera and took picture after picture after picture...
Then in SONY VEGAS 9 I put the shots together with a music track to create a stop motion video.
Please Suscribe to my Filming Company: www.youtube.com/4thdimensionfilming
www.fourthdimensionfilming.comacura tsx google translations
http://www.youtube.com/watch?v=r7peBLoE2uc
To achieve this video I used my digital camera and took picture after picture after picture...
Then in SONY VEGAS 9 I put the shots together with a music track to create a stop motion video.
Please Suscribe to my Filming Company: www.youtube.com/4thdimensionfilming
www.fourthdimensionfilming.com
How come after doing a motion to music, I'll continue doing it long after the music stops?
Like for instance, I was headbanging to some metal earlier, and throughout the day I've caught myself headbanging for no good reason. Same thing happens to me when I listen to ska music. When I listen to it, it sends my entire body in motion. However, when I'm sitting or laying down, my right leg will bounce up and down uncontrollably.How come after doing a motion to music, I'll continue doing it long after the music stops?The repetitive motion programs your muscles. This is called muscle memory. It's how we remember dances, martial art forms, athletic skills, or playing an instrument. Our body naturally wants to repeat this motion that brought us pleasure.
Monday, January 30, 2012
What is the best way to weatherproof the plastic box for a motion sensor originally intended for indoor use?
The motion sensor in question is a cheap Quorum Passive Infrared Detector (RR-150/A-160/G4567) powered by a 9V DC battery that emits 5V for about 1 sec when activated. The trick is that I also want to solder leads to the battery contacts so that I can power it using a wall transformer. It comes in a plastic box that is totally unsealed; so far I have considered either using a glue gun to seal all seams and holes, or putting the whole thing inside another plastic (or plexiglass) box. For the moment I am most concerned about water leakage, but it is possible that temperature is an issue, too, I suppose. The sensor will be used in a temporary outdoor installation for six months this summer.What is the best way to weatherproof the plastic box for a motion sensor originally intended for indoor use?Get a tube of RTV. It's a kind of silicone caulk. Try hardware stores, auto parts stores, or maybe radio shack. Apply a smooth bead to every seam and to the hole where the wiring enters the box...and about 2 inches or so of the wiring. Don't force it in to deep or it may interfere with the sensor. It goes on sort of like caulk. After you apply a bead to the seams smooth it with a wet finger. The smoothing is mostly for cosmetic reasons but will also help make a good waterproof seal. Make certain when you mount it that it is several inches off the ground, to avoid water splashing up on to it, and as much out of the weather as possible.
What horizontal force must be applied by the worker to maintain the motion?
A stockroom worker pushes a box with mass 11.1kg on a horizontal surface with a constant speed of 4.00 . The coefIficient of kinetic friction between the box and the surface is 0.240m/s.What horizontal force must be applied by the worker to maintain the motion?If the force calculated in part (A) is removed, how far does the box slide before coming to rest?Take the free fall acceleration to be = 9.80 m/s^2What horizontal force must be applied by the worker to maintain the motion?Normal force is equal to gravity Fn = m*g. Friction force is Ff = 0.24*Fn = 0.24*m*g. For box to move with constant velocity applied force should be equal friction force: F = Ff = 0.24*m*g.
When force removed, net force is equal to Ff, so acceleration is a = Ff/m = 0.24*g. Sliding would go for D = v^2/2a = v^2/(0.48g)
When force removed, net force is equal to Ff, so acceleration is a = Ff/m = 0.24*g. Sliding would go for D = v^2/2a = v^2/(0.48g)
How does the human mind perceive motion?
Think of a waterfall.
Water, as you probably know, is constantly changing - the spray as the water droplets collide off one another, in the river bed where the water is drawn into the soil and roots of nearby plants, even the sounds of water slapping against rocks suggest motion.
But this can only be translated using a momentary image - i can only communicate these things though a single point at a time, like a photograph taken from a camera.
What would be difficult, would be to describe the vast picture of water, of evaporation and condensation and precipitation and the huge volume of water that takes up two thirds of this planet's surface mass.
Even then, i would fail to describe to you what motion is, or how motion occurs.
From a philosophical perspective, how does the human mind perceive motion?How does the human mind perceive motion?From Vanderbilt University:
The bigger and brighter an object, the harder it is to perceive its motion
Bigger and brighter isn't better, at least not when trying to view moving objects.
That is the counter-intuitive result of a study performed by a team of Vanderbilt psychologists which sheds new light on one of the most sophisticated processes performed by the brain: identifying and tracking moving objects.
"The bigger an object, the easier it is to see. But it is actually harder for people to determine the motion of objects larger than a tennis ball held at arms length than it is to gauge the motion of smaller objects," says Duje Tadin, first author of the paper on the study appearing in the July 17 issue of the journal Nature. Tadin is a graduate student in psychology at Vanderbilt and his co-authors are postdoctoral fellow Lee A. Gilroy and professors Joseph S. Lappin and Randolph Blake.
In the article, the researchers show that this unexpected result is due to the way in which visual signals are processed in the part of the brain known as the medial temporal visual area or MT, one of the 30-plus cortical centers involved in processing visual signals. Their findings support the hypothesis that the neurons in MT employ a mechanism called "center-surround receptive field organization." This same mechanism, which acts to highlight differences, is found in a number of other senses, including touch, hearing and smell.
In the visual system, the center-surround organization is a clever way that nature has developed for filtering out spurious signals caused by shifting patterns of light that fall on the retina that don't have anything to do with the movement of objects in the external world.
One of the most difficult things that the brain does is pick out objects from the visual background. Objects can differ from the background in a number of different ways, including texture, color, brightness, binocular displacement (the difference in image placement in each eye due to the distance between them) and motion. So the brain uses these and a number of other visual clues to pick out individual objects.
Information from the eyes goes first to the primary visual cortex at the very back of the brain. Here the information is separated into different characteristics, such as texture, color, brightnes and motion.
But how does the brain "see" motion? Just detecting shifting light patterns is not enough. Each time you shift your eyes or move your body, for example, the patterns on the retina change in ways that must be ignored. That is where the researchers think that center-surround receptive field organization comes in. Neurons in the primary visual cortex relay motion information to the neurons in MT, an area that Vanderbilt neuroscientist Jon Kaas helped discover. Experiments indicate that in the center of the visual field MT each neuron "monitors" an area that is the size of a tennis ball held at arms length. However, each neuron is not just affected by what happens in this central area. It is also influenced by the responses of the neurons that monitor a surrounding area about the size of a soccer ball (held at arms length).
The central-surround mechanism works as follows. Each neuron has a preferred direction: right, left, up, down, sideways, et cetera. If a neuron that prefers right motion detects a motion to the right while the neurons in its surround area are not registering any motion, then it fires vigorously. If the neurons in its surround area are stimulated by leftward motion, however, then it sometimes fires even more vigorously. But, if the surrounding neurons are also registering motions to the right, the neuron does not fire. This inhibitory effect is the hallmark of the center-surround mechanism.
"This is what causes moving objects to stand out distinctly even against moving backgrounds," Lappin comments, "But when objects are the size of the surround area or larger, then they tend to be treated as background motion and so are less visible."
The researchers discovered this effect when they analyzed the results of a series of psychophysical experiments in which human observers were asked to determine the direction of motion of patterns of varying speed, size and contrast that were flashed briefly on a screen. Not only did these experiments confirm that people have more trouble determining the motion of larger objects, they also showed that this effect was greatest in conditions of high contrast. The influence of surrounding neurons weakens as contrast levels decline.
"This shows that the visual system adapts to the amount of information available. When visual information is plentiful, it uses a differentiation strategy to identify moving objects. As light levels drop, however, it switches to an integration strategy that uses the available information more efficiently," says Lappin.
Once the researchers had successfully documented the odd side-effect of this motion-enhancing mechanism, tHow does the human mind perceive motion?your eyes are like a camera and when you wave pictures ware they look like there moving thats how your eyes do stuffHow does the human mind perceive motion?Actually the motion of an object is perceived by the lower neurological levels of the brain. The mind is that activity that you use to help you coordinate between what your senses perceive and what is needed to be done in order to coordinate with that motion.
Water, as you probably know, is constantly changing - the spray as the water droplets collide off one another, in the river bed where the water is drawn into the soil and roots of nearby plants, even the sounds of water slapping against rocks suggest motion.
But this can only be translated using a momentary image - i can only communicate these things though a single point at a time, like a photograph taken from a camera.
What would be difficult, would be to describe the vast picture of water, of evaporation and condensation and precipitation and the huge volume of water that takes up two thirds of this planet's surface mass.
Even then, i would fail to describe to you what motion is, or how motion occurs.
From a philosophical perspective, how does the human mind perceive motion?How does the human mind perceive motion?From Vanderbilt University:
The bigger and brighter an object, the harder it is to perceive its motion
Bigger and brighter isn't better, at least not when trying to view moving objects.
That is the counter-intuitive result of a study performed by a team of Vanderbilt psychologists which sheds new light on one of the most sophisticated processes performed by the brain: identifying and tracking moving objects.
"The bigger an object, the easier it is to see. But it is actually harder for people to determine the motion of objects larger than a tennis ball held at arms length than it is to gauge the motion of smaller objects," says Duje Tadin, first author of the paper on the study appearing in the July 17 issue of the journal Nature. Tadin is a graduate student in psychology at Vanderbilt and his co-authors are postdoctoral fellow Lee A. Gilroy and professors Joseph S. Lappin and Randolph Blake.
In the article, the researchers show that this unexpected result is due to the way in which visual signals are processed in the part of the brain known as the medial temporal visual area or MT, one of the 30-plus cortical centers involved in processing visual signals. Their findings support the hypothesis that the neurons in MT employ a mechanism called "center-surround receptive field organization." This same mechanism, which acts to highlight differences, is found in a number of other senses, including touch, hearing and smell.
In the visual system, the center-surround organization is a clever way that nature has developed for filtering out spurious signals caused by shifting patterns of light that fall on the retina that don't have anything to do with the movement of objects in the external world.
One of the most difficult things that the brain does is pick out objects from the visual background. Objects can differ from the background in a number of different ways, including texture, color, brightness, binocular displacement (the difference in image placement in each eye due to the distance between them) and motion. So the brain uses these and a number of other visual clues to pick out individual objects.
Information from the eyes goes first to the primary visual cortex at the very back of the brain. Here the information is separated into different characteristics, such as texture, color, brightnes and motion.
But how does the brain "see" motion? Just detecting shifting light patterns is not enough. Each time you shift your eyes or move your body, for example, the patterns on the retina change in ways that must be ignored. That is where the researchers think that center-surround receptive field organization comes in. Neurons in the primary visual cortex relay motion information to the neurons in MT, an area that Vanderbilt neuroscientist Jon Kaas helped discover. Experiments indicate that in the center of the visual field MT each neuron "monitors" an area that is the size of a tennis ball held at arms length. However, each neuron is not just affected by what happens in this central area. It is also influenced by the responses of the neurons that monitor a surrounding area about the size of a soccer ball (held at arms length).
The central-surround mechanism works as follows. Each neuron has a preferred direction: right, left, up, down, sideways, et cetera. If a neuron that prefers right motion detects a motion to the right while the neurons in its surround area are not registering any motion, then it fires vigorously. If the neurons in its surround area are stimulated by leftward motion, however, then it sometimes fires even more vigorously. But, if the surrounding neurons are also registering motions to the right, the neuron does not fire. This inhibitory effect is the hallmark of the center-surround mechanism.
"This is what causes moving objects to stand out distinctly even against moving backgrounds," Lappin comments, "But when objects are the size of the surround area or larger, then they tend to be treated as background motion and so are less visible."
The researchers discovered this effect when they analyzed the results of a series of psychophysical experiments in which human observers were asked to determine the direction of motion of patterns of varying speed, size and contrast that were flashed briefly on a screen. Not only did these experiments confirm that people have more trouble determining the motion of larger objects, they also showed that this effect was greatest in conditions of high contrast. The influence of surrounding neurons weakens as contrast levels decline.
"This shows that the visual system adapts to the amount of information available. When visual information is plentiful, it uses a differentiation strategy to identify moving objects. As light levels drop, however, it switches to an integration strategy that uses the available information more efficiently," says Lappin.
Once the researchers had successfully documented the odd side-effect of this motion-enhancing mechanism, tHow does the human mind perceive motion?your eyes are like a camera and when you wave pictures ware they look like there moving thats how your eyes do stuffHow does the human mind perceive motion?Actually the motion of an object is perceived by the lower neurological levels of the brain. The mind is that activity that you use to help you coordinate between what your senses perceive and what is needed to be done in order to coordinate with that motion.
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