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. A

    Stress Energy Tensor - Confusion about signs and metrics

    Hi everyone. I'm working on deriving Friedmanns Equations from the Einstein Field Equations. I've got the '00' components worked out but I'm having some trouble with the spatial indices 'ii' of the stress energy tensor ## T_{ii} ##. I'm the FLRW metric with c=1 and signature (-,+,+,+) so that...
  2. X

    Confusion about physics vectors in question

    Homework Statement Engineers perform a crash test with a minivan and a compact car. The mass of the minivan is 800kg and the mass of the compact car is 560kg. The minivan was moving north, and the compact was was moving east. After the collision, the two cars crumpled together and moved at...
  3. C

    Understanding Time Dilation: A Confusing Experiment Explained

    I've seen an experiment with a light clock that explains time dilation. A photon is fired and gets reflected off of 2 parallel mirrors. It keeps bouncing back and forth like that, with each bounce qualifying as one tick of the clock. And it looks like that from a stationary reference frame. Now...
  4. X

    Understanding Taylor Series for Solving Complex Equations

    Homework Statement f(x)=\frac{4x}{(4+x^{2})^{2}}Homework Equations \frac{1}{1-x} = \sum x^{n} The Attempt at a Solution How am I supposed to use that equation to solve the main problem. I have the solution but I don't understand how to do any of it. My professor is horrible, been on...
  5. J

    Cross Sectional Area, Stress and Strain confusion

    Homework Statement For each material calculate the cross sectional area in m². Each sample is of rectangular cross section 20mm by 1mm. Produce Stress and Strain tables for the data. TEST DATA FOR X (N) EXTENSION (mm) 1000 0.48 2000 0.60 3000 0.70 4000 0.80 Homework...
  6. O

    Transformation of Vectors Confusion

    I've just started reading Arfken's book on mathematical methods for physics, and one of the very first sections is really confusing me. He is discussing the rotation of coordinates, and defining a vector as an object whose components transform in the same way as the coordinates do under a...
  7. M

    Gaussian Mixture Model Confusion

    Hi All, I'm trying to implement the Gaussian Mixture Model for background subtraction as described by Chris Stauffer and W.E.L Grimson in their paper "Adaptive background mixture models for real-time tracking." I'm having a little trouble with the logic in the step that updates the mean...
  8. S

    Complex current density of sphere confusion

    Hello, I am a bit confused on how to get this into the proper form, $$ \begin{eqnarray} \vec{J} &=& \vec{v}\rho \\ &=& (\vec{\omega} \times \vec{r}')\rho_o \Theta(R-r') \\ &=& \omega r' \sin(\theta')\rho_o \Theta(R-r')[\cos(\phi')\hat{y} - \sin(\phi')\hat{x}] \\ &=& \vdots \\ J_x + i J_y &=&...
  9. B

    Net torque, electric dipole confusion

    Hello all, I am so confused on why a net torque on a dipole in a uniform electric field would not be equal to zero. Wouldn't one end rotate clockwise, the other counterclockwise and cancel out to zero? Thanks.
  10. ash64449

    Still confusion in relativity of simultaneity and time dilation .

    Still confusion in relativity of simultaneity and time dilation... Hello friend, Still Something in my mind is saying that Relativity of simultaneity is the reason for time dilation even though i had some corrections in my understanding by posting various threads. Well,let me use Einstein's...
  11. O

    How Do Parallel and Orthogonal Orientations Affect Line and Plane Equations?

    I having trouble understanding the difference between parallel and orthogonal in relation to finding the relevant line or plane equations. Example; Determine the vector and Cartesian line if: a) passes through (2,1,-3) and is parallel to v=(1,2,2) What would happen if it was...
  12. E

    Confusion in electric potential energy

    This is an extract from my book ... " We define the potential V at any point in an electric field as the potential energy per unit charge associate with a test charge q0 at that point: V=U/q0." I don't know why did the book bring the test charge q0 now in the frame. Shouldn't the potential be...
  13. H

    Confusion about tension and pulleys

    Homework Statement I am a little confused about the concept of tension as it relates to pulleys. I am studying torque right now, and it says in the textbook that the tension in the rope around a pulley produces a torque that causes the pulley to turn. I don't fully understand this. I thought...
  14. L

    Time evolution of operators as projectors - confusion

    I have a confusion regarding expressing operators as projectors in Schrodinger and Heisenberg pictures. Please help. Consider a two-state system with |1> and |2> We know that e.g. a raising operator can be expressed as: \hat{\sigma}_+=|2><1| But here's my line of thought: In the...
  15. E

    A confusion in work and potential energy

    This is an abstract of my book " Potential energy is always defined relative to some reference point where U=0. Therefore U represents the work that would be on the test charge q0 by the field of q if q0 moved from an initial distance r to infinity. If q and q0 have the same sign, the...
  16. Sunil Simha

    Confusion Regarding Most Probable Kinetic Energy of an Ideal gas

    Homework Statement Find the most probable kinetic energy of an ideal gas molecule. Homework Equations v=sqrt(2RT/M) where v= most probable velocity k= Boltzmann's constant T= temperature of the system M= molar mass of the gas Maxwell's formula of...
  17. I

    Confusion regarding a proof for an infinite limit property.

    Assume for some real number L and c \displaystyle\lim_{x\rightarrow c} f(x) = ∞ and \displaystyle\lim_{x\rightarrow c} g(x) = L We must prove \displaystyle\lim_{x\rightarrow c} [f(x) + g(x)] = ∞ Let M > 0. We know \displaystyle\lim_{x\rightarrow c} f(x) = ∞. Thus, there exists...
  18. F

    Confusion regarding delta definition of limit

    I don't quite get the significance of the delta limit definition, if n>N and |sn−s|< ϵ , why does the limit converges does this simply means that there exist a number ε such that if n is great enough it will be greater than s by ε? But this doesn't make sense, because s is the value...
  19. H

    Dark Energy Confusion - Unraveling the Mystery

    Hi guys, I'm a bit confused. The initial motivation for including dark energy seems to be: "The Friedmann equation requires a flat universe to have a mass/energy density exactly equal to the critical density. Yet, observationally, including both the baryonic and dark matter, we can only find...
  20. S

    Induced drag confusion - More than one cause?

    Hi, I'm a bit confused by induced drag on an aerofoil and hoping somebody can clear it up for me. I understand that as air slips around the edges of the wing due to the pressure differential between the top and the bottom surfaces, the angle of attack at the ends of the wings is...
  21. I_am_learning

    Confusion regarding SI base units

    What qualifies for being called a fundamental quantity and having its own fundamental unit? For example length is considered fundamental quantity and it has a unit of meter. But Area isn't considered fundamental. Is it because we know area can be CALCULATED by multiplying the length of the two...
  22. A

    Understanding Critical Numbers and Inflection Points in Calculus

    I am a bit confused over something that should be relatively easy to research , however, I am having a hard time finding a direct answer to my question. When finding the extrema of a function , we find at what points the first derivative is 0 or undefined .. with the stipulation , if I am...
  23. nomadreid

    Confusion on application of definition of degrees of freedom

    I am confused about the counting of degrees of freedom. Yes, I know that it is the number of vectors which are free to vary. But that definition gives way to different interpretations: (1) the number of data points minus the number of independent variables. This seems to be the basis of the...
  24. S

    Electric potential reference points confusion

    Hi gang, I am hoping you can clear something up for me. When evaluating the potential of a solid sphere, I find myself confused about the volumes used such that, \phi = Q \int_{\infty}^R \frac{1}{V_1} r^2 \sin(\theta) \, dr \, d\theta \, d\phi + Q \int_R^r \frac{1}{V_2} r^2 \sin(\theta) \...
  25. A

    How can I differentiate between decimal and dot product notation?

    I was helping my cousin with his homework when i came aacross this problem... I can easily differentiate b/w 3.5 ( three point five) and 3.5 ( three dot product five) when they come in different situations.. but there was this equation written which had the term 3.5. I interpreted it as decimal...
  26. K

    Confusion about curved manifolds

    Hello fellow mathematicians! I am currently confused about the mathematics of curved manifolds. When introducing the affine connection on our bundle it seems to be an object totally determined by our coordinate chart. But since we can compute objects describing the curvature from the...
  27. E

    Amperes Law conceptual confusion.

    For amperes law it is stated that: ∫Bdl=μIenc My confusion is that B is that for example here now on Earth if I have a compass. It interacts with a the magnetic field of the Earth and points north. There is no I-enclosed yet there is still a magnetic field? Also another Amperes Law...
  28. M

    Where Should I Place the Gaussian Surface When Applying Gauss's Law?

    In calculating the electric field bw two parallel plate i.e a capacitor I encountered a problem :where to take the Guassian surface..When I consider the Guassian surface.a cube bw the two plates Electric intensity becomes 0..But when I take the Guassian surface with a portion of capictor inside...
  29. G

    Notation confusion; |\pi N; I, I_3> states

    Notation confusion; ## |\pi N; I, I_3 \rangle ## states In my book it says for the ##\pi N ## state: ##|\pi N; \frac{3}{2},\frac{3}{2}\rangle =|\pi ;1,1\rangle | N; \frac{1}{2},\frac{1}{2}\rangle## firstly, does this mean: ##|\pi N; \frac{3}{2},\frac{3}{2}\rangle =|\pi ;1,1\rangle...
  30. V

    Some confusion about balanced forces

    Hi, My question is: 1)When an object falls to the ground, shouldn't the ground exert a force greater than the weight of the object to stop its motion altogether? Because if the forces experienced by the object the moment it strikes the ground are equal and opposite in direction, then that...
  31. I_am_learning

    Confusion regarding encapsulation

    I am reading on Object Oriented Programming and I feel a bit uncomfortable with the concept of Encapsulation. And I keep wondering, how can someone 'accidentally' COMPOSE code (to change data) ? We far more frequently accidentally mistype and misspell than accidentally compose code. If a...
  32. E

    Solar Power - Photovoltiac cell confusion

    I have been trying to understand how PV cells work in solar panels and have become a bit confused, here is what I have read so far: The PV cell is basically a PN junction diode with a conductive connection on the P and N material between this connection there is a load, a lamp for example...
  33. P

    Algebra step confusion and unnatural completing the square

    Let f(x) = ax - \dfrac{x^3}{1+x^2} where a is a constant Show that, if a ≥ 9/8 then f'(x) ≥ 0 first problem when taking the derivative in the solution they seem to have jumped a step which I don't see how: f'(x) = a - \dfrac{3x^2(1+x^2) - 2x(x^3)}{(1+x^2)^2} = \dfrac{a + (2a - 3)x^2 + (a...
  34. O

    MHB Confusion in proof involving lim and liminf

    In a proof showing that the vector space of all functions from a metric space X to the complex numbers C is complete under the supremum norm, there was a line near the end that i was confused about. starting here: \(sup|f - fn| \leq liminf_{m \to +\infty} ||f_n - f_m|| \) the next step then is...
  35. E

    Engineering What are the Unknowns in a KVL Circuit Loop?

    1.http://imgur.com/d2lf8sa 2. V=IR 3. I feel like the answer should just be .012 because 1.2/100. Apparently that is wrong. If that is truly wrong. I also found I3 to be 3.25mA because 3.9 volts in parallel and V=IR
  36. A

    Understanding formula F=GmM/r^2 confusion help

    Homework Statement Scientists want to place a 2900.0 kg satellite in orbit around Mars. They plan to have the satellite orbit a distance equal to 1.6 times the radius of Mars above the surface of the planet. Here is some information that will help solve this problem: mmars = 6.4191 x...
  37. I like Serena

    MHB The Geometry of Complex Numbers and the Confusion of $e^{i\pi} + 1 = 0$

    I was looking at the header of MHB and I suddenly thought... wait! What does it mean?! I mean, it says:$e^{i \pi} + 1 = 0$ Now, I understand that if you calculate $e^{i \pi} + 1$ that you get 0. But you can also rewrite it as:$-1 = e^{i \pi}$ But how is that correct? Isn't $-1$ multivalued...
  38. Q

    Proper time: confusion over what it means

    Can anyone explain proper time with a simple example analogous to real life please? I am having a problem understanding it. Thank you
  39. G

    Solve Gas Laws Confusion - P, V, T & n

    Hey guys ! I am confused when textbooks say that P (pressure), V (volume), T (temperature), n (moles) or any combinations of these be CONSTANTS. Especially when it comes down to the three gas laws. I don't understand what some variable being a constant means :( and hence the immense confusion...
  40. C

    Confusion on wording of a dimension problem

    the speed v of sound waves in a gas can be express in terms of the pressure p and the density q (mass per unit volume) of the gas, as v=ap^bq^c, where a, b, and c are dimensionless constants. The dimensions of pressure are m/((LT)^2). What must be the values of b and c. I am confused on...
  41. V

    Born-Oppenheimer approximation confusion

    Hi, I'm reading about the Born-Oppenheimer approximation for a solid and they're doing the formalism of it. They say that we can basically consider the ions stationary with respect to the electrons because they move so little and so slowly in comparison to them. They say that ##R_i## are the...
  42. M

    Confusion between Attenuation and Intesity change

    Dear All, I am basically from Bio background and doing research in Insect Physiology as Phd. Currently I am given a task to generate artificial insect songs using a software. I did it with 3 v Noise stimuli(1.5 peak to peak) and fed it to amplifier and I heard it on Amplifier. So now the...
  43. DiracPool

    What is the relationship between angular momentum and energy in electrons?

    I'm a little fuzzy on the meaning of the angular momenta in electrons. From my understanding, the orbital angular momentum of an electron can have integer values of h-bar and the intrinsic "spin" can be 1/2 (and both can be positive or negative). How does this relate to the energy of the...
  44. T

    Understanding the Cosine Rule: Deriving the Other Two Formulas

    So here is my question, I understand how to derive the cosine rule from, both triangles acute and obtuse. My problem is the 3 formula you get from this equation. When I derive from a triangle I get the formula: c^2=a^2+b^2-2abcos∅ so how do you derive the other two formula, I read that...
  45. K

    Where Does the Coordinate Basis Approach to Lie Groups Break Down?

    Hello! I am currently trying to get things straight about Lie group from two different perspectives. I have encountered Lie groups before in math and QM, but now I´m reading GR where we are talking about coordinate and non-coordinate bases and it seems that we should be able to find commuting...
  46. V

    Schools Confusion about physics grad school.

    Hi I am currently studying at university of melbourne (Australia) major in mathematical physics and I just finished my second year. I plan to continue my graduate study in physics in US because i think the reputation of universities there are better. According to what i read from Caltech...
  47. D

    Complex operations, bra-ket notation, confusion

    Sorry for disregarding the template; I'm not really working out a homework problem as much as just trying to follow the reasoning in the text. I'm working through the first chapter of Quantum Mechanics, McIntyre, and I'm a little bit confused by the following. The text introduces bra-ket...
  48. L

    Solving 6/(2[1+2]), 3(3)=1 Confusion

    Of course the answer is 9. But my question is, some sources say this is written ambiguously. as in, 6/(2[1+2])=1 or 3(3)=1 Why do some people say one needs to evaluate what is effecting the parenthesis before dividing from left to right? I don't see anything in order of operations that...
  49. D

    Confusion with Friction and mechanical energy

    Homework Statement A sphere rolls from rest down a slope without slipping. Show using energy considerations that the speed of the sphere once it reaches the bottom is V = \sqrt{\frac{10gh}{7}} Homework Equations mgh = \frac{1}{2}mv^{2} + \frac{1}{2}Iw^{2} The Attempt at a Solution...
  50. P

    Confusion about light exerting a force

    Hello everyone! I've been thinking about this for a little while and haven't been able to come up with a satisfying answer yet, so I'm asking you guys. I've heard about things like solar sails, where the light from the sun would be used to push something to somewhere. I also heard...
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