Confusion Definition and 1000 Threads

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. D

    Confusion about combining resistors in series.

    Hello, everybody. I'm reading through my EE textbook and I'm having some confusion about when to combine resistors in series. The following figure is in my book: I see that they combine the parallel resistors of 6Ω and 3Ω to make the equivalent circuit shown in 2.42b. What I'm confused...
  2. A

    Confusion on displacement question

    Homework Statement A car moves east at 18 m/s for 5 minutes. What its displacement? It says that the answer to this question from my teacher is: 5400 m. Homework Equations → → X= v *t The Attempt at a Solution → V= 18 m/s [E] t= 5 min. → → → X= v *t =...
  3. D

    Continuous Map to Single Point: Clarifying Confusion

    Hi all, I need help with a paragraph of my book that I don't understand. It says: "the map sending all of ℝ^n into a single point of ℝ^m is an example showing that a continuous map need not send open sets into open sets". My confusion arising because I can't figure out how this map can be...
  4. 5

    Confusion with probability models and intersection of events

    Homework Statement I will use an example to showcase my confusion: Suppose a person watches show A 2/3 of the time, show B 1/2 of the time, and both show A and show B 1/3 of the time. For a randomly selected day, what is the probability that the person watches only show A? For a randomly...
  5. P

    Calculating Center of Mass with Added Particles

    http://examsolutions.co.uk/a-level-maths-papers/Edexcel/Mechanics/Mechanics-M2/2010-June/paper.php Question 3) part a) I got the answer to be 2.5 which is correct part b) I don't really get how to do this, I understand as a new particle is being added which is the same mass of the...
  6. M

    Is 0.27 nN/nm equal to 270N/km in unit conversion?

    Hi everyone, I'm having a little confusion here: I measured a value which is 0.27 nN/nm and I converted it's value as 0.27 N/m. Is this correct or should it be 0.27 nN/nm = 0.27*10^9 N/m Thanks for your help
  7. dexterdev

    Confusion in Power gain and voltage gain in decibels

    Hi all, I have a very basic doubt. If we have an amplifier with voltage gain A = Vo/Vi , where Vo is output and Vi is input voltages and Ap = Po/Pi which is power gain. Ap = Po/Pi = Vo^2/Vi^2 = (Vo/Vi)^2 In decibels powergain = 10 log (Po/Pi) = 20 log (Vo/Vi). In most tech...
  8. J

    Understanding Basic Mechanics: Solving the Confusion on Force and Speed

    Hello, I just started basic mechanics and what seems to mess with me is this: take a 1kg cube in a string, with how much force do you need to push it to give it the even speed of 2M/S, In the book it says F1-F2=0, so 9,8N=F2, so you have to push it upwards with 9,8 Newtons... but how the hell...
  9. N

    Confusion regarding pulldown resistors.

    Hi, I am having some confusion regarding pull down resistors. In the schematic I have a 100k pulldown resistor. P1 is the output port and the nOE(OE bar) is the input to a buffer. What is confusing me is if the P1 input is high impedance then the nOE should go high, but when the P1 pin...
  10. R

    Confusion with units for Power Required Formula

    Hi all, I'm having trouble with the power required formula for steady level flight. Here's the formula: Preq = 4/3*W*sqrt(W/S*2/ρ*sqrt(3*CD0/(π*ε*A))) I'm using this for a small indoor RC fixed wing. The values I'm using are as follows: Weight, W = 0.3924N Wing Area, S = 0.073 m^2 Density, ρ...
  11. K

    What Is the Maximum Safe Depth for the Submarine with a 40cm Window?

    Homework Statement A research submarine has a 40.0cm -diameter window 8.70cm thick. The manufacturer says the window can withstand forces up to 1.20×10^6N . What is the submarine's maximum safe depth? Homework Equations P= atmosheric pressure + ρg(depth) Pressure = Force/crossectional...
  12. R

    Slight confusion concerning Newton's first law

    Hi, I've very recently begun physics self-teaching as I used to find it boring and thus avoided it as a subject but now find it increasingly interesting. Nevertheless, I'm having some problems regarding questions on Newton's First Law. One of the questions in the book I'm using says the...
  13. J

    Velocity change by force in one and two inertial frame confusion

    Hi, I just finished class and my professor was writing some of Newton's Laws on the board and derived some equations. We ended up with: V(Δt)=FΔt (this is for velocity in first inertial frame V(2Δt)=2FΔt (this is for velocity in second inertial frame Then he went and got the position in...
  14. P

    Confusion regarding continuity equation in electrodynamics

    Suppose I have two charged particles with charge densities ρ1(r,t) and ρ2 (r,t) with corresponding velocity fields V1(r,t) and V2(r,t). Can I write continuity equation for the combined system? Wouldn't charges moving with different velocities would contribute differently to the current which...
  15. N

    Confusion with an inequality involving norms

    Homework Statement Hello, I'm little bit confused about a particular inequality in a proof: | (D_j f_i) (y) - (D_j f_i) (x) | ≤ | [(f'(y) - f'(x)]e_j | ≤ ||f'(y) - f'(x)|| The last part of the inequality confuses me. Is the absolute value (norm on R) less than any other norm on R^n?
  16. L

    Confusion created by notation in E&M

    I just started an E&M class and right from the beginning the notation seems so confusing it has to have been done as a joke. Trying to do a problem I run into about 10 different r's I have to keep track of. Capital R Lower case r Lower case r prime The r in spherical coordinates The "squiggle" r...
  17. H

    Proving the Oddness of 3n-2 Using Direct Proof

    Homework Statement im supposed to use a direct proof to prove that if 1-n^2>0 then 3n-2 is odd for all n∈Z Homework Equations The Attempt at a Solution if you let n∈z then suppose that 1-n^2>0 then 1>n^2 but the only inter n such that 1>n^2 is 0. 3x0-2=-2 as -2=2(-1), -2 is even ...
  18. E

    Moment Of Inertia of broken disk or ring confusion

    We all know that M.I of a Uniform rigid rod about an axis perpendicular to it's length and passing through it's center is MLsquare/12.Where M is mass and L is length of the rod. If it is broken to half such that M becomes M/2 and L becomes L/2,we can't apply ML square /12 formula to it.We have...
  19. C

    Confusion about Wave / Particle Behaviour of X-Rays

    Greetings, I am a Physics instructor teaching a course on Physics for Medical Radiologists and have a question to further my own understanding of wave / particle behaviour of X-Rays as used in x-ray image production. My background is more in climate / geophysics. The textbooks available for...
  20. N

    Confusion about notation regarding compliments/universal sets

    Im not sure how to interpret the notation, specifically the one on the left, the one on the right seems like you just include everything in the universal set? what does it mean when the line goes over everything? what does it even mean when the line is over the and/or symbol
  21. P

    Confusion about the speed of light

    So everyone knows the speed of light is a universal constant. However in many phenomena involving light it is useful to think that light is 'slowing down' like light travels slower in glass/ water then it does in a vacuum. How can this be if it is a universal constant?
  22. B

    How Do You Calculate Time from Velocity and Distance in Physics Problems?

    Homework Statement A baseball pitcher is known to throw a pitch with a speed of 105 miles per hour. In how many seconds will the pitch reach the catcher if the mound is 20 meters away? (assume 1600 m in 1 mile) Homework Equations v=d/t The Attempt at a Solution Idk how to...
  23. C

    Confusion Field Tensor and derivation of Maxwell's equations

    Hi as I'm reading http://www.maths.tcd.ie/~cblair/notes/432.pdf at page 13 I see that he states that the covariant and contravariant field tensors are different. But how can that be? Aren't they related by F_{\mu \nu} = \eta_{\nu \nu'} \eta_{\mu \mu '} F^{\mu ' \nu '} ? and is not the...
  24. A

    Lens Formula Confusion: Convex Lens, Cartesian Sign Conv.

    The cartesian sign convention for a convex lens is follows: 1. All distances on the principal axis are measured from the optical center. 2. The distances measured in the direction of incident rays are positive and all the distances measured in the direction opposite to that of the incident...
  25. C

    Understanding the Composition Rule and Transformation Law in Weinberg's QFT

    Hello, a confusion has arose during my so far study of the above book. According to the composition rule (2.3.11) it should be: U\left( \Lambda ,a \right)=U\left( \mathbf{1},a \right)U\left( \Lambda \right) and according to transformation law (2.5.3) and the eigenvalue equation which follows...
  26. C

    Understanding the Random Walk: Exploring the Average Distance After N Steps

    I read about the random walk the other day. The simplest 2D form, where you start at zero and move up or down one unit at random, both are as likely. To get an the average distance from zero after N steps, the following argument was used: The distance after one step is 1. If after some steps...
  27. D

    Why Does the Car Move When Pushing a Heavier Bus?

    If a car is pushing a bus (and the two both move in the direction of the car), I understand that the amount of force with which the car pushes against the bus is equal to the force the bus pushes back on the car. What I don't understand is why the car moves. Is it going forward with the same...
  28. D

    Which Approach is Correct for Nodal Analysis in Electricity Books?

    In nodal analysis method, two books use different and contradicting approaches and not sure which one is correct. One books says that currents at each nodes should be treated independently from the other nodes so that the same current can have two opposing directions in the same equations. The...
  29. L

    Confusion about derivative operators

    As far as I understand, the momentum operator is: \hat{p} = -i \hbar \frac{\partial}{\partial \hat{q}} Where I'm not sure at this point if it's mathematically correct to talk about a derivative wrt. the position operator - but the point is, as far as I understand, that this equality is true...
  30. B

    Dirac delta function, change of variable confusion

    The Dirac delta "function" is often given as : δ(x) = ∞ | x = 0 δ(x) = 0 | x \neq 0 and ∫δ(x)f(x)dx = f(0). What about δ(cx)? By u=cx substitution into above integral is, ∫δ(cx)f(x)dx = ∫δ(u)f(u/c)du = 1/c f(0). But intuitively, the graph of δ(cx) is the same as the graph of...
  31. N

    AZING! How does the 3rd law explain the forces acting on a book on a table?

    Confusion on Newton's 3rd law! According to the 3rd law, the equal and opposite forces are acting on two different bodies and therefore cannot cancel each other. They are mutual forces. Why then, so we say the force of gravity on say, a book on a table, and the normal force acting on the book...
  32. C

    Schools Confusion over to leave the college I am going to attend

    Sorry, for I did not know where to put this question. But this subforum's name seemed suitable to me to put my following query, here. I am really in a dilemma these days ( on whether to leave or not). Actually , I was rejected from the university , I liked most and in my list of 5-6...
  33. S

    Cause and effect confusion, BJT

    Lets take a simple BJR transistor having an Rc. The Ic = beta*Ib, of course. But Ic=(Vcc-Vce)/Rc as well right? Now the confusion, does Ib cause Ic or is Ib possible without Ic (and thus no Vcc)? If we have Vcc and thus Vce than we shall have Ic thus we can have Ib=Ic/beta? What causes Vce, is...
  34. M

    Positive/Negative Symbol Confusion

    So since we know that electrons are flowing in a relatively less negative (relative positive) direction why does + indicate source? Surely the electrons are flowing towards the + and not from it.
  35. A

    Confusion about how the momentum is transferred

    I'm thinking of non pyrotechnic ways to make changes in the velocity of a satellite in space and my concepts here might be totally wrong, but i wondered if transfer of momentum might work. That is, as in the first image if i have a small mass compressed by a spring and i release it later by...
  36. R

    Confused by Metric Space Notation: What Does It Mean?

    I have a simple question about the notation. I want to be more correct with notation, I don't understand exactly what the notation is saying. In regards to a Metric space A metric space is an ordered pair (M,d) where M is a set and d is a metric on M, i.e., a function {{\bf{d: M \times...
  37. T

    Can the group velocity be understood intuitively using the dispersion relation?

    While studying the brillouin zone I came across the dispersion relation and the group velocity. The group velocity is given by v=dω/dκ, I understand this in the sense of beats where it is Δω/Δκ and I understand that the group velocity is the propagation speed of the envelope function. However...
  38. S

    Double slit confusion from observed particle dynamics.

    Hey Guys, I continue to get mixed messages about the nature of electron behaviour during the double slit experiment. I have heard the term observation used to describe an interaction with the electron (Obviously necessitating a change in it's behaviour to facilitate the ballistic outcome)...
  39. Z

    Confusion of circle and sphere for physics problems

    Homework Statement The problem is attached Homework Equations P=F/A The Attempt at a Solution I did the question like this (got wrong answer though): Surface area of sphere=4∏r2=4×∏×0.252 Atmospheric pressure=1.01×105 Force=1.01×105×4×∏×0.252≈80000N Actual answer 20000N...
  40. J

    Do Generators Run Out of Electrons?

    So, when you generate electricity, you spin a magnet pushing the electrons in the surrounding wires and creating a stream of electrons, now the confusion... If you do this for some time, wouldn't the electrons in the wires run out? I mean there is only a certain number of loose electrons on the...
  41. E

    Inductor/coil/choke design confusion

    Hello all, i have an equation for flux density taking the inductor chrecteristics into account as Bmax= (Vrms * 10^8)/(4.44*A*N*f) but the company i work for has given it at Bmax=(Vl * 10^4)/(4.44*A*N*Vss) where Vl = voltage across inductor. i am finding a lot of variation for...
  42. S

    Quantum Confusion - Does not exist until it's observed and age of universe

    Quantum Confusion -- "Does not exist until it's observed" and age of universe Hi. I ran across this: http://physics.jamesbaugh.com/quanta.html QUOTE: "It is a problem of assuming values of properties are "out there" independently of the acts by which the values are determined. The...
  43. Z

    [C] Circular-linked list ; finding a value ; pointer confusion

    Hi, So I have a circular linked list; each element of the list has a int value and a next pointer to the next element. BUT. When I try to compare rather the NEXT element has a certain value, I always get a true return; how do I properly compare the structure values with an int? I'm doing...
  44. R

    Confusion about vertical polarization and horizontal polarization

    Could you please help me to understand some basic concepts about antenna polarization. The books I have are really confusing and do not have examples that I can learn from. Please look at the attached E plane radiation pattern image I attached (figure 13). The books image (figure 13)...
  45. C

    Bit of confusion with coils and electromagnetic induction

    Apparently for emf to be induced in a coil, the magnetic field (or part of it) has to act along the normal to the coil face. So does this mean that the coil moves side-ways through the magnetic field? where instead of moving through its length (its longer side), it moves through the coil face...
  46. M

    Confusion about squeeze theorem example; plugging 0 into x when x ≠ 0.

    This is from a textbook but it is not a homework problem, it's an example following the introduction of the "Sandwich Theorem". It says "for all x ≠ 0", but then it appears to assume that x = 0 when it finds the limits of g(x) and h(x). Clearly 1 ≤ u(x) ≤ 1 means u(x) = 1, I don't dispute...
  47. S

    How do you simplify summation expressions?

    I understand that they have done \displaystyle\sum_{r=k-1}^{2k} r =\sum_{r=1}^{2k}r - \sum_{r=1}^{k-1-1}r But where did r = 1 come from as r = k-1 before is what I don't understand. Also this question: Show that \displaystyle\sum_{p=3}^{n}(4p+5) = (2n+11)(n-2) \displaystyle4\sum_{p=1}^{n}p...
  48. E

    Quantum Physics Confusion: Black Bodies & Spectrums

    Well, am an Alevel student... Edexcel.. I just find quantum physics a really really confusing topic.. My question is particularly in black bodies. If we consider the sun as a black body, where did the radiations of the sun initially come from. I don't mean the emitted radiation we see, i mean...
  49. J

    Confusion on Farad calculation

    Hi, Please apologize the ignorant question, but I am confused on applying the discharge capacity of a capacitor. If Farads = Coulombs/Volt, then a hypothetical 1 Farad capacitor could generate 1 volt at 1 amp for one second. But by the same formula, a .00005 Farad capacitor could generate...
  50. J

    Transition in LS-coupling confusion

    Transition in LS-coupling confusion ! :) Hello :) Lets take for example a 2 electron system with l1,s1 and l2,s2. One electron changes energy due to electric dipole. I understand the rules for electrons in electric dipole transitions: 1) Δl = +/- 1 (parity flips) 2)...
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