What is Head: Definition and 411 Discussions

A head is the part of an organism which usually includes the ears, brain, forehead, cheeks, chin, eyes, nose, and mouth, each of which aid in various sensory functions such as sight, hearing, smell, and taste, respectively. Some very simple animals may not have a head, but many bilaterally symmetric forms do, regardless of size.
Heads develop in animals by an evolutionary trend known as cephalization. In bilaterally symmetrical animals, nervous tissues concentrate at the anterior region, forming structures responsible for information processing. Through biological evolution, sense organs and feeding structures also concentrate into the anterior region; these collectively form the head.

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  1. E

    What Are the Equations of Motion for the Print Head Control System?

    Homework Statement Please refer to the image attached for problem statement and diagram. There's an inductor somewhere, but I have no idea where and I don't know how to accommodate for it. I can also see that there's another energy storage device, the spring on the right. I have no idea...
  2. D

    How fast must the astronaut's head be moving

    Homework Statement In this device, an arm 8.84g long rotates about one end in a horizontal plane, and the astronaut is strapped in at the other end. Suppose that he is aligned along the arm with his head at the outermost end. The maximum sustained acceleration to which humans are subjected in...
  3. M

    Draw the vectors head to tail so they make a triangle

    Draw the vectors head to tail so they make a triangle
  4. S

    Calculate Distance to Drop Egg on Physics Professor's Head

    Homework Statement You are on the roof of a physics building, which is 46.0 m above the ground. Your physics professor, who is 1.80 m tall, is walking alongside the building at a constant rate of 1.20 m/s. If you wish to drop an egg on your professor's head, how far from the building...
  5. M

    Epistemic Perspective : Meanings ARE in the head

    Constructive criticism please: In 1975, Hillary Putnam published a paper entitled “The Meaning of ‘Meaning’”, in which he proposed an interesting “thought experiment” (see Putnam, H; “The Meaning of 'Meaning'” In Philosophical Papers, Vol. 2: Mind, Langauge and Reality. Cambridge University...
  6. P

    News Highest gdp per head of population

    Which country has the potential to have the highest GDP per head of population if its economy was run perfectly? Can one country run a perfect economy if its trading partners do not? Is there a country that can get by on its own with internal markets?
  7. L

    Gaining a Head Start with First Year Physics: Resources and Motivation

    I'm about to begin a bachelor of science with a physics major. I've already found some books on electrodynamics and relativity and such, but I can't find the motivation nor resources to intepret some of the more abstract mathematics, especially to do with linear algebra, tensor analysis and...
  8. P

    Liquid static head vs. dynamic head?

    It's been a looooooong time since I delved into fluid properties. I'm trying to predict flow based on a known static head. I have a water column which will result in 6 psig of static head. The height of the water column will not change during the flow. I know the downstream piping will...
  9. Y

    I don't know how to calculate a tennis racquet head size thanks

    Hi everybody, The area of a tennis racquet head size is like an egg shape, not oval shape. how to calculate it? Thank you so much for your help ^_^
  10. Math Jeans

    Which songs are stuck in your head?

    Just asking the PF members out of interest (and because this stupid Dragonforce song won't go away). Which songs always get stuck in your head?
  11. P

    Fluids - Head Loss complicated

    Homework Statement Heated air at 1 atmosphere and 35 deg. Celsius is to be transported in a 150 meter long circular plastic duct (smooth) at a rate of 0.35 cubic meters/sec. If the head loss in the pipe is not to exceed 20 meters, determine the minimum diameter of the duct. Homework...
  12. L

    Probability of 5th Tail Before 10th Head

    "A fair coin is flipped repeatedly. What is the probability that the 5th tail occurs before the tenth head?" What I have so far: So the 5th tail has to come before 10th head. So if we take getting a tails as success and after the 9th head, we MUST have 5 tails --> we can only have 14...
  13. G

    Bug lands on a frictionless sphere. Show that the Bug leaves head when

    Homework Statement A bug lands on top of the frictionless, spherical head of a bald man. It begins to slide down his head. Show that the bug leaves the head when it has dropped a vertical distance 1/3 the radius of the head. Homework Equations Not sure. Maybe: E_f - E_i = 0...
  14. F

    PhD Thesis: Searching for the Right Lab

    So, I've been very busy shopping around for labs to apply to for my Phd thesis. Last week I went to a conference where I heard a talk on a new discovery that really captured me and made me want to to my thesis work there. I looked the guy up and it turns out, he's from one of the top tier...
  15. A

    Coin toss with rule +1 if it is a head and -1 otherwise

    Coin toss with rule "+1 if it is a head and -1 otherwise" 25 < my age < 54. Start from the number of my age and toss a fair coin, plus one if it is a head and minus one otherwise, on average, you need to toss 210 times to hit the bound, i.e. 25 or 54. There are two integers satisfying the...
  16. Saladsamurai

    What Is the Best Way to Solve Integrals Involving Exponential Functions?

    because I keep getting jammed up here, Using u substitution \int \frac{dx}{e^x} I don't see what else to let u equal besides e^x. ...
  17. P

    Head loss due to sudden expansion

    Hi all, I'm sure a lot of you know about the head loss due to sudden expansion: Hl = (1/2g)*(v1-v2)^2 This equation can be derived from Bernoulli, continuity and momentum balans equations. The underlying assumption in deriving this equation is that the pressure just after the expansion...
  18. Ivan Seeking

    Is This the Worst Cologne Ever?

    Mmmmmm, tastes like chicken.
  19. A

    Fluid Velocity Head - Get Practical Information for Designing Piping System

    Hi, Does anyone know where does the velocity head (the v2/2g term in the Bernoulli eqn.) fits in when designing a piping system? i.e, what useful practical information can one have by calculating the velocity head? Thks
  20. S

    Medical What is that ringing sound in the head?

    Hey guys, what is that ringing sound we hear in our head? I read in a taoist book that if we concentrate on it, it can finally be silenced and we will hear true silence where every sound will be clear but it won't bother through its clarity in the sense of annoyance but it will be beautiful. I...
  21. H

    Calculate Probability of Winning Head and Tails Game

    I ve got this simple problem and I can can not find the solution. Two men play head and tails. Each man flips the coin n times, every time he has head, he should add one point to his score. At the end, they compare the scores, whose score has more points , the man is the winner. A is the...
  22. B

    Can someone explain head to tail bunch differential acceleration?

    I was given an assignment involving finding the head to tail bunch differential acceleration of a beam of muons loading onto an RF cavity, and it occurred to me that my understanding of the concept might be keeping me from working the problem. Can somone concisely explain it to me?
  23. B

    Head to tail bunch differential acceleration

    Homework Statement Calculate the head to tail bunch differential acceleration from beam loading on an RF cavity. Homework Equations Frequency 201 MHz Stored energy varies as E^2 Acceleration varies as E Use any other variables that might be needed The Attempt at a Solution...
  24. W

    How Does Adding Mass Affect the Angular Speed of a Spinning Disk?

    A horizontal disk of diameter 12.0cm is spinning freely about a vertical axis through its centre at an angular speed of 72 revolutions per minute. A piece of putty of mass 5.0g drops on to and sticks to the disk a distance of 4.0cm from the centre. The angular speed reduces to 60 revolutions per...
  25. S

    What causes equal head loss in 3 pipes of different diameters?

    Hey, If you have 3 pipes of different diameter flowing into another.. what needs to be true for the head loss in the 3 pipes to all be equal? ie Hf1 = Hf2 = Hf3 Cheers. :S
  26. P

    What is the angle at which the neutron rebounds?

    Homework Statement A neutron collides elastically with a helium nucleus (at rest initially) whose mass is four times that of the neutron. The helium nucleus is observed to rebound at an angle Theta2 = 45° from the neutron's initial direction. The neutron's initial speed is 6.6x 10^5 m/s...
  27. K

    Why Do Sparks Occur at the Head of an Electric Train?

    Homework Statement When an electric train runs,we are familiar to the sparks at the end of cable connections.Why does it occur?Is it due to voltage fluctuations? Homework Equations The Attempt at a Solution
  28. edward

    World Record Set: Kicking Oneself in the Head!

    This guy sets the world record for kicking oneself in the head. I don't think I will enter this one.:rofl:
  29. S

    Finding angles quickly in your head

    Here's the free-body diagram of a stupid physics problem I had: http://img211.imageshack.us/img211/5081/triangleey9.png When going over this problem both my book and my lecturer say that \alpha = \theta (they actually don't even mention \alpha; they just write it as \theta to begin with. I...
  30. A

    Tub/Shower Head: Fluid dynamics question

    I installed a shower head in a customer's bath tub last week. The customer was not happy with the flow of water coming from the shower--so I removed the shower head and noted the orfice that leads to the spray area in the shower head was only 3/32" in diameter. I drilled a hole enlarging the...
  31. D

    Doing math in your head - Post Calculus

    Hello, I am finished with Calc III and now am in a Mathmatical Methods course. For the first day we were given a "Prerequisites Inventory", basically problems we should know. But I can't do most of them! If you can help me with any I would appreciate it.Homework Statement #4 If cos(24)...
  32. D

    The Feynman Lectures Over my head?

    I have always seen these books in the stores, and such, and they're 100 on amazon (which is a heck of a lot better than B&N) and i want them, but then again they'll probably shoot right over my head. I'm working through my first year of high-school physics. I have read quite a few books on...
  33. J

    Reviving Clogged Print Head Jets: Tips and Tricks for Inkjet Printers

    I know I've been asking a lot of questions lately, but here's another. Does anyone know of a way to unclog the jets on the print head of an inkjet printer? I have the kind of printer where the print head and ink tanks are seperate. I've tried disassembling and soaking them in water, warm water...
  34. Integral

    Exploring the Heceta Head Lighthouse B&B on 1 Dec Birthdy

    1 Dec is \frac {dy} {dx} birthday so we spend the night before at a B&B on the Oregon coast. This was view from our window: http://home.comcast.net/~integral50/hecetaHead/HPIM0326a.JPG here is a bad pic of the B&B. It is in the Heceta Head lighthouse Keepers house...
  35. S

    SONAR and reflection head on

    Two submarines are underwater and approaching each other head-on. Sub A has a speed of 12 m/s and sub B has a speed of 17 m/s. Sub A sends out a 1520 Hz sonar wave that travels at a speed of 1522 m/s. ... I already solved for this question ... ... What is the frequency of the sound detected by...
  36. G

    Why is my eyebrow healthier than my head hair?

    I noticed that my eye brow hair is substantially smoother,softer and healthier overall than my head hair? I know that part of the answer is that we touch and mess with head hair more but there must be another reason - at the molecular level. And is it possible to make my head hair as healthy?
  37. W

    Dice problem that I can't fully get my head around

    There's a probability question I saw on the web that looks innocent enough, unless you pay attention to the wording: I have two dice. If i roll them until i get a double, which is the most likely roll to get a double on? The answer given is below: The first roll is the most likely. Heres...
  38. I

    Medical Depression: It's All In Your Head.

    Medical Explanation for Major Depression An important line of defense in treating Major Depression is realizing depression is a medical disorder. It’s a BRAIN disorder, not a MIND disorder (although depression effects the mind). A depressed brain is not running on all cylinders. Certain...
  39. F

    Web journals may turn peer-review system on its head

    what does everyone think of this? although I've never had anything published nor even submitted anything i think i more or less agree with andrew odlyzko: http://www.cbc.ca/technology/story/2006/10/02/tech-peer.html i think journals like those would enable crackpots to get their...
  40. D

    Head Fall Acceleration Question

    Hello, I'm not particularly looking for the answers in this problem as much as I am looking for the method to the solution. It's been giving me a headache. 1. Traumatic brain injury such as concussion results when the head undergoes a very large acceleration. Generally, an acceleration...
  41. N

    Yet another question that is supposed to turn SR on its head

    This is something that arose out of a section in Richard Mould's Basic Relativity. He begins SR with his so-called "Physical Threorms (PT)," which are gedanken experiments used to show the effects time-dilation, length-contraction, and the concept of simultaneity in relativity, in that order...
  42. B

    Proving gcd(rs , r + s)= 1: I'm in Over My Head!

    I saw this on a website. Prove that if r and s are positive integers with r > s and gcd(r,s)=1, then gcd(rs , r + s)= 1. I can think of two ways to show this. Using the Euclidean algorithm or by showing that 1 can be a linear combination of rs and r + s. Funny thing...I couldn't do either...
  43. D

    Connecting iPod to Car Head Unit: Seeking Pinouts & Reliable Source

    I have a head unit (HU) for my car (Panasonic) with the ability to connect an external CD changer. The HU connection has an 8 pin DIN and a left and right RCA input for the external CD changer. I was hoping I could easily connect the left and right RCAs to my ipod and connect the 12v and...
  44. R

    In what direction should the plane head?

    Question: An airplane, whose air speed is 600km/h is supposed to flyy in a straight path 35 degrees north of east. But a steady 100 km/h wind is blowing from the north. In what direction should the plane head? Here is an answer by someone(is it right?) Vp (vector velocity of the...
  45. S

    Learn the Science Behind Human Hair and Its Unique Properties

    why when you cross the 2 hairs http://img148.imageshack.us/img148/8223/image15dz.png the moment you try to break them up, you would see like they are "somehow connected", is that "static electric" ?
  46. J

    I'll let you know how this turns out. Wish me luck!

    do-it-yourself encryption Really don't know where to put this, so thought I'd ask all the fine folks here and see if I get a response. One of the curses of being widely read is that sometimes you remember the subject but neither content nor location of something you read once and would really...
  47. T

    Head Loss Calculation: Discrepancies?

    I was reading on this page... http://www.cda.org.uk/megab2/build/pub125/sec4.htm#5.1 ...and I tried calculating head loss using both the forumla given, and the nomogram. Aren't these supposed to give the same result? Or am I missing something fundemental? Because they don't equal each...
  48. Danger

    Don't Lose Your Head - Negative Shock

    http://www.negative-shock.net/view-409" That woman must be absolutely boneless. :bugeye:
  49. A

    Head on Collision: Physics of X & Y Spheres

    Hi everyone, I've got a problem with solving this one. Two spheres X and Y (no mentioning about them being identical in mass but drawn in equal sizes) are about to collide head on. Their initial velocities are +5ms^-1 and -5ms^-1 initially, moving towards each other with X being towards...
  50. B

    What is the placement of the spark plug in an L head combustion chamber?

    hey guys , i am studying about the old combustion chambers. i came across the L head combustion chamber and am confused about the exact position of the spark plug.so please help me out of this.
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