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. AakashPandita

    Confusion regarding the concept of acceleration along a component

    Suppose we have a wedge with angle θ on which there is a block. We are pushing the wedge with the least force required to keep the block stationary. If the acceleration of wedge is A then the acceleration of the block along the inclined plane will be gsinθ+Acosθ=0. That means A is negative. How...
  2. D

    Why are transitions B and C allowed in the Selection Rule confusion?

    The solutions say transitions B and C are allowed. Does anyone know why we can neglect the rule about delta(m_j)=-1,0+1? I don't see any way to deduce the value of m_j values. Also if anyone could clarify what is meant by the small "l" and big "L" rules for the electric dipole that would be...
  3. A

    Confusion about the definition of adjoint representation and roots.

    Hi, I'm getting a bit confused about the adjoint representation. I learned about Lie algrebras using the book by Howard Georgi (i.e. it is very "physics-like" and we did not distinguish between the abstract approach to group theory and the matrix approach to group theory). He defines the...
  4. J

    Confusion over Pascal's Experiment

    I have been trying to understand pascal's barrel experiment in a more qualitative sense but I can't get my head around it at all. Pascal supposedly had a strong wooden barrel which he attached onto it a very thin pipe which was 20m tall. He then poured water into the top of the pipe until both...
  5. R

    Understanding Flyback Transformers: Exploring Voltage Induction and Turn Ratios

    Hey everyone, I'm a bit confused about how exactly the transformer works. What I have gathered from wikipedia is that basically what is happening is a low voltage DC is pulsed through the primary winding via a transistor, causing current build-up. When the pulse is through, the current in the...
  6. Ackbach

    Confusion on Body Definition in Y&F, 9th, 4-49.

    Homework Statement From Young and Freedman's University Physics, 9th Ed., Problem 4-49. Two blocks are connected by a heavy uniform rope with a mass of ##4.00## kg. An upward force of ##200## N is applied to the top block, which has a mass of ##6.00## kg. The lower block has a mass of ##5.00##...
  7. J

    Confusion with product-to-sum trig identities

    I'm having some confusion with a couple trig identities. On wikipedia (http://en.wikipedia.org/wiki/List_of_trigonometric_identities#Product-to-sum_and_sum-to-product_identities), the following two identities are listed: sinθcosβ = (1/2)[sin(θ+β) + sin(θ-β)] and sinβcosθ =...
  8. S

    Extreme Confusion of centripetal acceleration force and normal force

    Hi guys, first off, thanks for answering my previous question... Now here's another one. I got confused by my school's homework a bit...so there's a car that travels over a humpback bridge with a radius of 45m, so basically it's a semicircle bridge, and so I'm supposed to calculate the...
  9. J

    Confusion with Michelson-Morley Experiment

    Please can someone help me as I really don't understand the Michelson-Morley experiment - there seem to be (from what I have read) two different versions on it. Both versions assume the same apparatus where two light beams are sent out perpendicular to one another. One version says that if a...
  10. J

    Energy and conservation of momentum confusion

    If you consider a bullet firing from a gun then you have conservation of momentum and a Newton's third law pair (according to what i have read on the internet anyway). They both experience the same force if they are a third law pair but, generally, what is it that determines which object...
  11. K

    Work against gravity confusion

    Hi I've just started learning work, energy etc and the first question in the book is in the form: An object of mass m is lifted by a tension through a displacement of h. Find the work done on the object. I know that the answer is simply mgh J, there is something that I don't quite get...
  12. Q

    Confusion about the accelerating expansion of the universe and Hubble

    My school textbook says that discovery of the 1a supernova was what led to the understanding that the universe expansion is accelerating but doesn't hubble's equation already suggest that the universe would expand at an accelerating rate? V = Hd (V = velocity, H = hubble's constant, d =...
  13. T

    Word Problem Confusion: Am I Right or Nitpicky?

    I will occasionally get problems wrong because the "right" answer should be y=nx, but I put x=ny, is the program being nitpicky or am I somehow misreading the problem?
  14. AakashPandita

    Confusion regarding notation of instantaneous velocity wrt something.

    I know that v(t)=dx/dt Then what is v(x) and how? Is it also dx/dt or something else?
  15. M

    Confusion about integration constant

    After solving a DE I ended up with (y3)/(3x3) + ln(x) = c and initial conditions y(1) = 2. If I just plug in straight away I get (23) / (3(13)) + ln(1) = c which is c = 8/3 but if I multiply the equation by 3x3 first: (y^3) + (3x3)ln(x) = (3x3)c and the 3 goes into the c and solving for c I...
  16. C

    Current reference direction confusion

    Homework Statement I have two questions. 1) The ends of a length of wire are labeled a and b. If the current i from a to b is negative, are electrons moving toward a or b? 2) We have a circuit element with terminals a and b. The voltage and current from a to b are both positive. If...
  17. X

    Basic physics confusion in my structure

    My physics core is a little bit weak, and this one question confuses me. Homework Statement A 3kg box sits on top of a 7 kg box. The object accelerates at 1 m/s^2. Find the force applied on the bottom block; if there are no forces besides this one. Homework Equations F= ma The...
  18. X

    Confusion; one block on top of another block

    Can anyone help me out with this? Here's the question 1. Homework Statement A 2.2 kg block sits on top of an even bigger 3.2 kg block. The coefficient of kinetic friction between the two blocks is 0.25. The coefficient of static friction between the 3.2kg block and the floor is 0.32 Find the...
  19. D

    Is acceleration related to distance traveled?

    Hi this is my first post... May be I am doing something wrong... I was thinking about a unit acceleration of 1ms-2 ,let an object be accelerating 1ms-2 and at rest the object's velocity was 0ms-1 and after 5 seconds its velocity was 5ms-1 ,so it will cover a distance of 15 meters after 5...
  20. thrush

    Confusion about Lorentz Transform

    Hi! I am new here, thought to join as I am trying to learn Relativity, in this case Special Relativity. I have solved a bunch of problems already but ... The Lorentz Transform formulation I am dealing with is a 4x4 matrix. I understand the invariance of the spacetime interval and have...
  21. V

    Engineering Parallel RLC circuit confusion

    Homework Statement Find vL(0+) Homework Equations V=IRThe Attempt at a Solution I have an exam tomorrow and so I'm in a bit of a hurry so please excuse the horrible drawing. The problem I'm having with this question is a conceptual one. I've found vL in this this circuit by first finding...
  22. S

    Understanding Vector Addition in Physics

    I am stuck on this one: According to me, the only correct answers are \vec{r} = \vec{t} - \vec{s} \\ \vec{r} + \vec{s} = \vec{t} But according to the key, these are also correct \vec{r} + \vec{t} = \vec{s} \\ \vec{s} + \vec{t} = \vec{r} I honestly do not see how, can somebody...
  23. D

    Temperature CONFUSION in derivation for Helmholtz Free Energy

    Dear all, I have been spending 12 hours on this and cannot seem to come up with a solution. We derive Helmholtz Free Energy (A) from the second law of thermodynamics. dS(Total) = dS(system) + dS(surrounds) we try to express dS(surrounds) with properties of the system. Assuming...
  24. L

    Confusion with Einstein tensor notation

    Homework Statement I'm confused about writing down the equation: \Lambda \eta \Lambda^{-1} = \eta in the Einstein convention. Homework Equations The answer is: \eta_{\mu\nu}\Lambda^{\mu}{}_{\rho}\Lambda^{\nu}{}_{\sigma} = \eta_{\rho\sigma} However it's strange because there seems...
  25. C

    Confusion between Comp. Eng. and Comp. Science

    I am recently going to undergo my second year in Computer Engineering and my dream job is to work in cyber security. I always thought that I could work in Cyber security with a major in Computer engineering but I have been told that it is Computer Science not engineering, but I heard this from...
  26. S

    Confusion about Noether's theorem

    Hi, I keep running my brain in circles while trying to get a solid grip on Noether's theorem. (In Peskin and Schroeder they present this as a one-liner.) But I'm having trouble seeing the equivalence between "equations of motion are invariant" and "action is invariant (up to boundary term)"...
  27. C

    Motor Sizing for Two Mechanisms: How to Determine Required Torque?

    Hello all, I an trying to size a motor to drive two mechanisms but am having some real trouble getting my head around the required torque. First let me explain what we have. Basically there are two mechanisms where I have plotted the speed and torque requirements on this graph as you...
  28. K

    Solving for Vr and VL in an RLC Circuit

    Homework Statement Hi i got this question ? have to find Vr and VL so can i use this formula : VR = IR VL = I * XL? confuse ?? need help ?? am i on right track?
  29. T

    A bit of confusion on a simple thermodynamics problem.

    Homework Statement A house with floor space of 2000 ft^2 and average height of 9 ft is heated from an average temperature of 50 degrees F to 70 degrees F. Determine the amount of energy transferred in the house assuming: a) The house is air tight. b) Some air escapes through the cracks as...
  30. D

    Magnetic Field Energy Density Confusion

    I am trying to find the approximate force imparted on a piece of iron on the axis of a finite length solenoid. One website said a good approximation was to take the difference of the magnetic field energy from when the piece of iron was directly outside the solenoid and when the piece of iron...
  31. S

    Understanding Electrostatic Induction in Dielectrics

    During electrostatic induction,a posivitiely charged body is brought near to a uncharged body.During this uncharged body gets bound negative change toward the end of the body near to charged body. My question is in reality what happens to the electron and proton of uncharged body.Do the all...
  32. AakashPandita

    Confusion regarding direction of kinetic friction on inclined plane.

    please help! The formula for kinetic friction acting on a sliding body is μkN When the body is sliding with constant velocity down an inclined plane fk=μkN When the body is sliding up the inclined plane(say due to a force acting parallel to the inclined plane) with constant velocity...
  33. E

    Little confusion regarding centripetal force in vertical circle

    consider a pendulum. The mass 'm' is hung and now we are interested in finding the velocity so that it completes one circle. Clearly we can do it easily by conserving energy. Now my problem is with the top most point. Clearly the tension is minimum at this point so that string becomes slack...
  34. Mandelbroth

    Gauss's Law (Notational confusion)

    I'm familiar with the differential form of Gauss's Law, which reads that ##\nabla\cdot\vec{E}=\frac{\rho}{\epsilon_0}##, where E is the electric field, ρ is the charge density, and ##\epsilon_0## is the permittivity of free space. We can take the volume integral of both sides, and then use the...
  35. S

    Drift velocity formula derivation confusion

    In the derivation of drift velocity i have seen two variations and want to know which one's correct. s=ut +\frac{1}{2}at^{2} Assume that the drift velocity of any electron in any conductor is : v_{d}=l/t Due to the electric field the acceleration of electrons in any conductor...
  36. S

    MHB Is understanding limits necessary for senior-level real analysis?

    Regarding the post below in http://www.mathhelpboards.com/f10/epsilon-delta-proof-confusion-4745/: There are just two things left I need to wrap my mind around, after that I think I will have comprehended the epsilon-delta concept. In example 3 in the document epsilon-delta1.pdf where the...
  37. F

    Luminosity & flux equations confusion

    Hi folks First off I have only just figured out that v is used as bloody frequency in loads of astrophysics equations. Not fun. I've got monochromatic flux as: Fv = dE / dt·dA·dv now I'm happy with this. But now the lecture notes I'm looking at describes monochromatic luminosity as...
  38. S

    MHB Understanding Epsilon-Delta Proofs for Beginners

    In a epsilon-delta proof, one wishes to show that 0 < |x-a| < \delta implies |f(x) - \text{L}| < \epsilon. But every example that I have seen, one always begins with the "then"-part, namely the conseqeunt |f(x) - \text{L}| < \epsilon, and work backwards to arrive at something reminiscent of 0 <...
  39. M

    Confusion with Disconnected sets

    Hello, I am having some difficulties understanding why a subset under the usual metric topology of the reals is connected. How can a set X = (0,1] u (1,2) be connected? The definition I am using is: A is disconnected if there exists two open sets G and V and the following three properties...
  40. C

    [Hanging/Sliding Chain Problem] Confusion in Normal Force

    This is a very basic problem which you all must have seen somewhere. But recently an itching doubt has come up to me regarding this problem. Problem: A chain lies on a table with some part of it hanging over the edge. Now if the coefficient of friction is μ, then find out the maximum part...
  41. J

    Two-Variable Optimisation Confusion

    Hi, So f(x,y) = xe-x(y2 - 4y) Find all stationary points and classify them i got for fx(x,y) s.p (1,4),(1,0) for fy (x,y) s.p (0,2) I thought that you don't need double differentials at this stage and if it is a s.p it must satisfy for fx(x0,y0) = 0 for fy (x0,y0) = 0 which...
  42. O

    Notation Confusion in Linear Transformations

    I'm just having trouble understanding some of the notations given, when attempting questions such as the following: {f\inF(ℝ,ℝ): f(3)=5}. Is it just saying that, the function 'f' spans all real values?
  43. J

    Cdf (Cumulative Density Function) Confusion

    Hi there, So regular i thought that the procedure was F(s) = ∫s0 f(x) dx However i am doing a problem with a kinked pdf and it is telling me to do something like F(s) = ∫s0 f(s) ds for 0=<s>=1/2 then... F(s) = F(1/2) + ∫s1/2 f(s) ds I am confused at the process of using f(x) or...
  44. U

    Confusion about Acceleration of an Object

    (I am a newbie in physics. I did not use the template when posting as this isn't really a homework question but about something that makes me confused in elementary physics). Suppose I have two objects (with masses m<M respectively) connected vertically by a wire such that the one with mass m...
  45. A

    SPST Relay Ratings and Operation Confusion

    I'm having trouble understanding the ratings for an SPST Relay. I need one with the following specs: Coil Rating: 12Vdc, Contact Rating: 20Amps @ 15Vdc If I use a relay with a 24Vdc Coil rating, does that mean that it would require 24Vdc to operate, or is that the maximum amount of...
  46. G

    Confusion about continuity in metric spaces

    I'm confused about the the definition of a function not being continuous. Is it correct to say f(x) is not continuous at x in the metric space (X,d) if \existsε>0 such that \forall\delta there exists a y in X such that d(x,y)<\delta implies d(f(x),f(y))>ε Is y dependant on \delta? It...
  47. nomadreid

    Confusion about normal probability plots

    The expositions for a normal probability plot (aka normal quantile plot) (in which observed probabilities are plotted against theoretical probabilities, or sometimes the other way around, to get a rough check as to whether a set of data is normally distributed by checking linearity) are not too...
  48. W

    Confusion on Continuity of Current and Free Charge in Conductor

    I know there must be something wrong with the following derivation based on Maxwell's equations but could not figure out what is wrong. The derivation deals with continuity of current and free charge in a conductor in general. Continuity of current says that, \nabla\cdot...
  49. A

    Confusion about gravity and the fundamental forces

    I understand that there are 4 fundamental "forces" of nature that we've identified; gravity, electromagnetism, and the two nuclear forces. However, I have been under the impression that gravity isn't a "force" in the same way that the others are. From what I figured, a force is something that...
  50. 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...
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