What is Confusion: Definition and 1000 Discussions

In medicine, confusion is the quality or state of being bewildered or unclear. The term "acute mental confusion" is often used interchangeably with delirium in the International Statistical Classification of Diseases and Related Health Problems and the Medical Subject Headings publications to describe the pathology. These refer to the loss of orientation, or the ability to place oneself correctly in the world by time, location and personal identity. Mental confusion is sometimes accompanied by disordered consciousness (the loss of linear thinking) and memory loss (the inability to correctly recall previous events or learn new material). The term is from Latin: confusĭo, -ōnis, from confundere: "to pour together", "to mingle together", "to confuse".

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  1. F

    MHB Uniform convergence confusion

    on page 4, example 9 in this link, http://www.personal.psu.edu/auw4/M401-notes1.pdf, they show a sequence of functions is not uniformly convergent. To show this, you need to show that for some epsilon, there is no 'universal' N. But they didn't pick a particular value of $z$, they chose...
  2. D

    Schwartz - Christoffel transformation: point at infinity confusion

    We know that the derivative of the general Schwartz - Christoffel map (function) is: f'(z) = λ(z - x_1)^{a_1}...(z-x_n)^{a_n} Question: In various sources around the web, it is mentioned that x_n can be taken to be the "point at infinity", and the last factor can be removed from the above...
  3. A

    Ohm's Law, Circuits, and Wires confusion

    I can do circuit problems, but conceptually I cannot figure out what is going on from a basic physics perspective, with respect to the following: Say you have a circuit with a battery (emf = V) and a resistor (resistance = R). Then, electrons on one side of the resistor are in a constant...
  4. U

    Sound Doppler shift asymmetry confusion

    I have come to learn that the Doppler shift equation is asymmetric. That is, the Doppler shift is not the same when source is moving towards the observer or when the observer is moving towards the observer (both with same speed). I have looked at the derivation of the Doppler shift equation...
  5. J

    Does Electron Cloud Distribution Affect the Repulsion Between Atoms?

    Why do atoms repel each other when their electrons aren't in any defined region of space? If we think of the electron as completely smeared out over the whole volume of the orbital, is the electric field just distributed evenly and continuously across it? Or do electrons always have a definite...
  6. H

    Wave-particle duality confusion

    Hi, I am a high-school student who recently finished the chapter on QM. I thought I completely understood it, but when I started to look back at what I’ve learnt, then suddenly, nothing really makes sense. And one of the things I find really really hard is the nature of electrons. My...
  7. Entanglement

    A confusion about the conception of work

    I've learned that a force is said to do work when it acts on a body and causes a displacement in the same direction of the force and that W = F.s ( when theta equals zero) But I have a problem understanding the concept. On Pushing a brick wall, carrying a bag heavy brick at a constant height, it...
  8. T

    Confusion about transformer and flux

    Lets consider an ideal transformer in no-load state, i.e. with the primary side connected to a voltage source, and the secondary side in open-circuit. Now, this is what I believe; the voltage Vp in the primary produces a current, which lags the voltage by 90°, as would be in an inductor. This...
  9. Z

    MHB Residues - complex analysis confusion.

    Hi! I am having a hard time with residues. :( I understand the formal definition of a residue, but anything past that and I am struggling. My course lecturer has a very confusing way of organising the course material and it is very hard to comprehend so was wondering if anyone could help with...
  10. J

    Vector Sum of a Standing Wave Confusion

    Hi, I was taught that a standing wave is formed when a progressive wave meets a boundary and is reflected. I was also taught that waves that meet a fixed end, reflect on the opposite side of the axis to the side that they met it at. (I hope that makes sense) If this is true, when the wave is...
  11. P

    Confusion regarding Kelvin-Plank statement of Second Law

    Hello there. New here. I have read and tried to understand the Kelvin Plank statement of the second law. Essentially, it would imply, it is impossible to convert a given quantity of heat completely to work. Why is it so? I mean, what is the justification for this? I am ready to...
  12. G

    Confusion of the electrical conductivity unit in CGS.

    Hello. Electrical conductivity is written as \frac{n_{e}e^{2}}{m_{e}\nu_{ei}} where n_{e}, e, m_{e} and \nu_{ei} are for electron density, charge, mass and electron-ion collision frequency. According to Wikipedea, http://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity Unit...
  13. nomadreid

    Dimensions of Hilbert Spaces confusion

    If I understand it, Hilbert spaces can be finite (e.g., for spin of a particle), countably infinite (e.g., for a particle moving in space), or uncountably infinite (i.e., non-separable, e.g., QED). I am wondering about variations on this latter. The easiest uncountable to imagine is the...
  14. A

    Confusion about a point and a line

    A point has no dimension and a line, which has dimension, is made from points together. How does something without dimension create something with dimension? I can't really make any sense of it. Could you share your opinions?
  15. A

    How Do Torque and Force Differ in Physics?

    Please look at pictures. What is it that Fv-Mg=-Ma? This does not make sense to me. Fv applies torque while Mg is a translational force. How can a force that is applied perpendicularly at a point of other than the center of mass cause translational motion?
  16. nomadreid

    Confusion over Brownian sample paths

    This question is in this rubric because I figured it belonged to measure theory, but I am ready to move it if I am wrong. In reading "Fractal Geometry" by Falconer, I see (Thm. 16.2 and comment following its proof) that the Hausdorff dimension of a Brownian sample path (a continuous function...
  17. M

    Fortran Fortran branching statement confusion

    Folks: I have a FORTRAN program published in Multivariate Morphometrics (Blackith and Reyment - 1971). In this book they list a FORTRAN program that computes Canonical Correlates. I don't have a FORTRAN compiler and I'm trying to translate this program into PERL. The one FORTRAN book that is...
  18. I

    Boolean Algebra Identities: How do they work?

    C) How did they go from the first red line to the second? f) How did they go from the first green line to the second g) B + B(bar) = 1, so surely the answer should have a +1 ? 2) How did they go from the first purple line to the second? I have a list of the Boolean laws and I have used...
  19. F

    Understanding Brillouin Zones - What do they represent physically?

    Hey all, Quick question about BZ's and it's probably a really dumb one. Solid State isn't my favorite class... What does it physically represent? Like is the area of the BZ divided by the area of a k-state (2π/L) equal to the number of charge carriers in the system? So if there was an...
  20. TheFerruccio

    Confusion over the definition of a Green's function

    This is how I learned about Green's functions: For the 1-D problem with the linear operator L and the inner product, (\cdot,\cdot), Lu(x) = f(x) \rightarrow u=(f(x),G(\xi,x)) if the Green's function G is defined such that L^*G(\xi,x) = \delta(\xi-x) I understand how to arrive at this...
  21. N

    2 dimensional collision confusion

    Homework Statement A 2 kg mass with initial velocity v = (5i + 7j) collides perfectly elastically with a 3 kg mass with initial velocity v = (-1i -3j) After the collision, the 2kg mass has a speed of √50 m/s and the 3 kg mass is traveling at an angle of 329.77Θ as measured from the...
  22. C

    Tangent vector to curve - notational confusion.

    Given a curve ##\gamma: I \to M## where ##I\subset \mathbb{R}## and ##M## is a manifold, the tangent vector to the curve at ##\gamma(0) = p \in M## is defined in some modern differential geomtery texts to be the differential operator $$V_{\gamma(0)}= \gamma_* \left(\frac{d}{dt}\right)_{t=0}.$$...
  23. J

    Confusion with free electrons in metals

    Hi, I'm really confused with how electrons become 'free' in a metal. I have a few questions and would be very grateful if someone could shed some light on them. 1. Are the electrons actually free? In a sense that the atom it is attached would essentially become an ion 2. If you take a copper...
  24. A

    2:4 decoder solution confusion

    Hi. I am confused a bit about the solution for 2:4 decoder in the picture below. Please help me with the question in the figure. Thanks.
  25. M

    Fortran Fortran DO loop sequence confusion

    I am trying to convert a FORTRAN version of a Canonical Correlates program listed in Multivariate Morphology - Blackith and Reyment. I've programed in FORTRAN decades ago and now I have to understand the language to rewrite the program into PERL. a) DO 260 I = 1 , M b) SX( I ) =...
  26. H

    Confusion over length contraction

    I understand why an object in a moving frame would be longer, but not why one in a stationary frame would be shorter. Wouldn't one in a stationary frame be the same as the object would be in the rest one? I understand the time dilation behind it, it's just that the rest of the reasoning makes no...
  27. nomadreid

    Confusion about basis vectors and matrix tensor

    In "A Student's Guide to Vectors and Tensors" by Daniel Fleisch, I read that the covariant metric tensor gij=ei°ei (I'm leaving out the → s above the e's) where ei and ei are coordinate basis vectors and ° denotes the inner product, and similarly for the contravariant metric tensor using dual...
  28. B

    Average kinetic energy/ temperature confusion

    My mcat book says temperature is a measure of the total kinetic energy of a system. Then later on it says temperature is a measurement of the average kinetic energy of a system. Is this an error? Thank you.
  29. T

    Active and Passive Transformations Confusion

    Hi all, I'm sort of struggling to understand the difference between active and passive transformations. I'm working with two books, and both say that in one case the vectors are transformed (active) and in the other the operators are transformed (passive). That's fine and dandy, but in terms...
  30. U

    Surface charge and volume charge density mathematical confusion

    If you have a charged solid sphere with uniform volume charge density ρ, then the total charge on the sphere is Q = ρ*4/3*∏*R^3 , where R is the radius of the sphere. Now...
  31. R

    Inertia and static friction confusion

    In a recent physics class I took, my teacher explained how friction is not affected by surface area, but by the "bumpiness" of the two objects and the mass, as well as other things, but not the surface area. But this made me wonder how nails get harder to pull out the deeper they are embedded in...
  32. K

    Conservation of Energy confusion

    Homework Statement A dog takes a running horizontal leap off a 10 m cliff and jumps with a speed of 3 m/s onto a ledge 4 m below the height of the cliff. With what speed does he land on the ledge?Homework Equations KEi + PEi = KEf + PEf 1/2mvi2 + mghi = 1/2mvf2 + mghfThe Attempt at a Solution...
  33. K

    Power Loss Confusion: I^2R vs V^2/R

    Power loss doubt: power loss = I^2 R Power loss = V^2 / R But the 2 equations are contradictory ,,, from the first equation , we can say " MORE THE RESISTANCE MORE THE POWER LOSS" from the second equation ,,, it is the other way round... Why does this happen? ( usually the 1st equation is used...
  34. R

    Newton's Third Law and the Conservation of Momentum

    Newton's third law confusion? If A exerts some force on B then it experiences a force of same magnitude and in opposite direction. This didn't seem intuitive to me so I thought of it this way, Let A and B be a single system. Now there is no net external force acting on the system so the...
  35. Z

    Sign confusion when taking gradient (Newton's Method)

    I'm watching a lecture on Newton's method with n-dimensions but I am kind of hung up on why the professor did not use the negative sign while taking the first gradient? Is there a rule that explains this or something that I'm forgetting? The rest makes sense but highlighted in red is the part I...
  36. Z

    Sign confusion when taking gradient (Newton's Method)

    I'm watching a lecture on Newton's method with n-dimensions but I am kind of hung up on why the professor did not use the negative sign while taking the first gradient? Is there a rule that explains this or something that I'm forgetting? The rest makes sense but highlighted in red is the part I...
  37. N

    Cartesian to polar confusion (simple)?

    Homework Statement Convert -2+2√3i to polar coordinates. Homework Equations r = √x2+y2 θ = tan-1(y/x) The Attempt at a Solution I am confused because θ = tan-1(2√3/2) = tan-1(√3) = -π/3 and r = 4, so that would make the polar form 4cis(-π/3), but the calculator gives: 4cis(2π/3). I...
  38. J

    Confusion to the solution of a MIT ocw problem

    Homework Statement My snipping tool is totally broken. So I'm going to leave a link :x It's problem 1.6 http://ocw.mit.edu/courses/physics/8-02-electricity-and-magnetism-spring-2002/assignments/ps1a.pdf Homework Equations E_{sheet}=\frac{σ}{2ε_{0}} E_{slab}=\frac{ρD}{2ε_{0}}...
  39. C

    Engineering Transformers open circuit and short circuit test confusion

    Homework Statement A 50 KVA,6360 V/230 V transformer is tested on open and short-circuit to obtain its efficiency,the results being as follows: O.C.: Primary Voltage-6360 V, Primary Current-1 A, Power Input - 2 kW S.C: Voltage across primary winding-180 V Current in secondary...
  40. X

    Exploring Coherent States in Quantum Mechanics: From Lasers to Photons

    So a coherent state in quantum mechanics is "the most classical" quantum state (A Gaussian wave packet), which satisfies the Heisenberg uncertainty relation with an equality. This allows the wave packet to travel in space in a more localized fashion (like a classical particle) because its...
  41. AbhiFromXtraZ

    Confusion On Electric Field Inside Capacitors

    When deriving capacity of a parallel plate capacitor, we consider the electric field (sigma/epsilon), i.e. the field due to one of the plates while both the plates are charged with Q and -Q respectively...so should not be the field due to both the plates, i.e. (2sigma/epsilon) since the...
  42. J

    What is the difference between unit vectors v and r?

    Follow the 1st ideia: \\ d\vec{r} = dr \hat{r} + r d\theta \hat{\theta} \\ \\ \frac{d\vec{r}}{dr} = \frac{dr}{dr} \hat{r} + r \frac{d\theta}{dr}\hat{\theta} \\ \\ \frac{d\vec{r}}{dr} = \hat{r} and now: \\ \frac{d\vec{r}}{dr} = \frac{d\vec{r}}{dt} \frac{dt}{dr} = \frac{d\vec{r}}{dt}...
  43. KingCrimson

    A little confusion with parallel circuits

    suppose that you have to wires connected in parallel, one double the length of the other now that means that the longer wire has double resistance . according to kirchhof's law , the current going in the two wires is the same as the current coming out , but if one is double the length of the...
  44. S

    Confusion about time dilation and length contraction

    Hi all, I tried searching for this but failed to find an answer to my question. I am having an issue with properly interpreting the equations for time dilation and length contraction. Let's assume that I am standing still and a train is passing by next to me (moving with uniform velocity). Let...
  45. S

    The direction of moments (no specific problem, just a confusion)

    Hi. For whatever reason I'm really struggling with figuring out the direction of a moment in two dimensional statics problems. How can I tell if it's CW or CCW? The right hand rule just confuses me even more and I cannot find any explanation that breaks it down simply enough for me to...
  46. Chronos

    Contracting Confusion: black holes and event horizons

    This paper, http://arxiv.org/abs/1402.3055 Black Holes, Firewalls and Chaos from Gravitational Collapse, reminds me why it is risky to get too close to a black hole. The authors suggest some the paradoxes posed by black holes may be a consequence of the cosmic censorship hypothesis. I may have...
  47. P

    Nodal analysis voltage confusion

    So the voltage across the R2 resistor is given as vT-0 = vT But then the voltage across the R1 resistor is given as "vT-Vs1" I'm not sure which two nodes the voltage across R2 involves. Is it the same as R1? Also, I am not sure of the voltage source vs1. Across which two points does it apply?
  48. V

    Solve MOSFET Confusion: Establish 0.8mA & 1.5V with Parameters VT, μpCox, L, λ

    Homework Statement The diagram: http://images.fr1ckfr4ck.fastmail.fm/probC.jpg This MOSFET has the following parameters: |VT| = 0.6V μpCox = 100 (μa/V2) L = 0.25μm λ = 0 Establish a drain current of 0.8 mA and a voltage VD of 1.5V. Determine the transistor width W, and the...
  49. ThomasMagnus

    Confusion over angle between vectors

    Homework Statement I have been doing dot and cross product recently. I get how to calculate everything; however, I am confused about which angle to use when asked to find the angle between two vectors. When you use the cross product, you always end up with 2 answers, for example 120° and...
  50. Solarmew

    Anti-reflective coating confusion

    My professor confused me today :( I'm trying to figure out the thickness of an anti reflection coating and it looks like from the equation 2ndcos(Θ) = mλ that for a given λ the thickness of the film should increase for incidence slightly away from normal. But he said that intuitively it...
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