Doubt Definition and 591 Threads

Doubt is a mental state in which the mind remains suspended between two or more contradictory propositions, unable to be certain of any of them. Doubt on an emotional level is indecision between belief and disbelief. It may involve uncertainty, distrust or lack of conviction on certain facts, actions, motives, or decisions. Doubt can result in delaying or rejecting relevant action out of concern for mistakes or missed opportunities.

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  1. S

    MOSFET Design Doubt: Explaining Positive Voltage

    Can someone explain this sentence in MOSFET design.. The Since the drain will be at a positive voltage relative to the source the two pn junctions can be effectively cut off simply connecting the substrate terminal to source terminal.
  2. Einj

    Doubt on sign of the propagator on Peskin

    Hi everyone. I was trying to reproduce the calculation needed to include the QCD correction to the low energy electroweak Lagrangian. In particular I am looking at Peskin section 18.2. In equation 18.35 an extra minus sign appears on the numerator of the second fermion propagator. Can anyone...
  3. K

    Doubt in Noise Vibration and Harshness (NVH)

    What does a first / second / nth order frequency mean physically?
  4. E

    Doubt in the basics definition of work

    Hello! In my studying of work I've always been told that work done (by what? ) = Force (component along its path) times the distance it moves. Mathematically, W=F.s ... My question here is what is the geometrical presentation of saying Force x Distance ... In other words, when we multiply...
  5. D

    Why is Alcor not considered part of Ursa Major?

    Hey folks i got a doubt, Alcor is behind of Mizar,very near and why Alcor doesn't make part of the Ursa Major? i mean the Ursa Major is compost of 7 stars and alcor doesn't make part. thanks for the attention.
  6. D

    Theia Impact: How Did the Earth's Hole Disappear?

    Hey people i have a doubt o try to be more specific this time, theia the planet collided with the Earth and created the moon this impact destroyed a large part of the Earth make a hole, what i like to know is how this hole who the planet Theia create on Earth disappeared, i mean the impact...
  7. T

    Simple doubt in work done by gas

    In First law of thermodynamics , work done by the gas is given by pΔV . I have few doubts regarding this- 1)Is 'p' ,pressure of the gas or external pressure of the surroundings ?If gas is expanding then surely gas pressure should be more than that of the surroundings and vica versa ...
  8. M

    Doubt in mass suspended by spring

    Consider a mass M, suspended by a weightless spring (horizontally or vertically). If I apply a force on the mass M, it executes simple harmonic motion. My question is for small displacement (that is pushed or pulled) according to Hooke's law F=-kx, it is equal to force we applied right...
  9. A

    Doubt on Fatigue Strength S-N diagrams

    A standard way of plotting an S-N (fatigue strength vs no of cycles) graph is to start off by taking a value of Sm (for N=1000) cycles and joining it to the point depicting Se(Endurance Limit). Now we commonly take Sm= 0.9Sut for steels. Now I was wandering, before you actually get to use the...
  10. A

    Doubt Regarding Shearing Stresses In a Beam

    Lets say we have a beam which is simply supported at the two extreme ends(support conditions don't matter in my question). A concentrated transverse load is applied at the halfway point. Now let's say we take a section at x= L/3 where is L the length of the beam. Now we know that transverse...
  11. A

    I have a big doubt. Is centripetal acceleration linear acceleration?

    It is generally said that centripetal acceleration is directed towards the center of the circular path along the radius. So can we say that centripetal acceleration is a linear acceleration. Is it or can it be represented along a straight line. I had a question in my exams. A kid is rotating a...
  12. bhanesh

    Why Does j.ds Have Closed Integral on Electromagnetics Equation?

    Why j.ds has ' closed integral ' on below equation
  13. MarcoAurelio

    Sign of acceleration due to gravity doubt

    I have a question, according to rules for the sign of x and y-acceleration; when I should use the negative sign for gravity (g) in a problem, because it's confusing since I've seen that according to my textbook when an object is free falling g is negative (therefore acceleration is -9.8 ms^-2)...
  14. A

    Doubt in Michelson Morley experiment

    Hi All, I studied about Michelson Morley experiment in my graduation in the compulsory Physics paper. I had Computer Science major(not a Physics guy:frown:), anyways this question came in my mind during my graduation time and may be because of my misinterpretation however couple of days ago...
  15. TrickyDicky

    Linear applications simple doubt

    Is an injective endomorfism automatically bijective?
  16. T

    Conceptual doubt in angular velocity

    Homework Statement I am having a few doubts while writing relationship between angular speed and linear speed ,in the reference frame of a moving observer . Suppose at an instant, car A is heading towards car B with velocity 'v'. Car B is moving towards right with velocity 'u' ,i.e along...
  17. C

    Entity relationship diagrams doubt

    I am doing a project of an entity relationship model and a doubt came: Should repeated attributes of the entities be shared? Or I must reproduce these to every entity? In another words, if two of my entities are books and magazines, shall I have a single publisher attribute, or one for each?
  18. C

    Classic rain falling on a car's window problem doubt

    A car travels due east with a speed of 50.0 km/h. Raindrops are falling at a constant speed vertically with respect to the Earth. The traces of the rain on the side windows of the car make an angle of 60.0° with the vertical. Find the velocity of the rain with respect to (a) the car and...
  19. R

    Engineering Diode logic doubt (digital circuit)

    Hello guys, I'm not getting the output of the diode logic circuits: http://upload.wikimedia.org/wikipedia/commons/1/1f/Diode-OR2.png If both inputs are 1, then there is current across the diodes then the output is 1, but shouldn't it drop because of the resistor R? If both inputs are...
  20. dexterdev

    A doubt related to infinitesimals in continuous fourier transform.

    Hi all, Only few days back I got the idea of probability density function. (Till that day , I believed that pdf plot shows the probability. Now I know why it is density function.) Now I have a doubt on CTFT (continuous time Fourier transform). This is a concept I got from my...
  21. M

    Doubt in electromagnetic spectrum

    In electromagnetic spectrum, why there is no radiation less than wavelength of Gamma rays and waves higher than the wavelength of Radio waves?
  22. E

    Is an equilibrium solution always zero in differential equations?

    I am still in the first few pages of my differential course. I just passed through the term equilibrium solution. Apparently, it meant for me as when the solution of the DE is zero. For example, dv/dt= 9.8-(v/5) ... has an equilibrium solution of 49 where dv.dt is actually zero. Is this the...
  23. T

    Interpreting Limits of Functions That Approach Infinity

    When the limit of a function turns out to be infinity ,how should we interpret it ? For ex. we have \lim_{x \to 0}\frac {1}{x^2} = \infty What does this mean ? Does it mean that the limit is ∞ or does it mean that the limit does not exist as ∞ is not a number ? I would appreciate if...
  24. D

    Doubt: Basic question on Work-Energy Method?

    I have a basic doubt on application of work energy method, 1. Can I apply work-energy method (i.e. work done equals to change in kinetic energy(KE)) for a body sliding down the inclined plane? If yes, while solving the problem i should use only change in KE or sum of change in KE &...
  25. mnb96

    Doubt on derivation of complex functions

    Hello, I have a doubt on how to differentiate a complex function f:ℂ→ℂ defined as follows: f(z)=zz^* where the * stands for complex conjugation. According to this source (at the very end of the Section, where it says: "...As this is a complex value, G*(f) acts as a constant...") the result...
  26. M

    Doubt in Law of mutual interaction

    Book: Classical mechanics (textbook) by Douglas Gregory (cambridge publications) Law of mutual interaction states that when two particle (let it be P1 and P2) interacts, the particle (P1) induces an instantaneous acceleration (a21) on particle P2 and the particle P2 induces an instantaneous...
  27. M

    Doubt in Inertial frame of reference

    Newton's laws of motions are not applicable in Non-inertial frames of reference which means only mutually accelerated frames of references, My question is how can we apply Newton's laws of motions for practical experiments such as simple pendulum, motion of a ball, etc. conducted in near surface...
  28. M

    Is Motion Quantifiable? Exploring the Scalar vs. Vector Debate

    Is Motion a scalar or vector or neither?
  29. A

    Doubt regarding rotations in spinor space

    Dear Sir, I am currently doing an advanced course in Quantum Mechanics. This current doubt of mine, I am unable to clarify it properly. It follows as: Spin 1/2 particles reside in 2dim-Hilbert space( Spinor Space)...However, we talk about rotations of states in this space where the angle...
  30. M

    Doubt in uniform circular motion

    why are we considering speed is constant to find velocity a particle in uniform circular motion, is it possible for a particle in a circular motion to have constant velocity?
  31. V

    Simple doubt in application of calculus

    I have done quite a few introductory physics problems where calculus is involved .When refreshing the concept of work done by variable force,I find myself unsure about an application of calculus.The underlying concept which is puzzling me is at the very root of calculus .The work done by the...
  32. V

    Simple doubt in induced charge

    When a positive point charge q is brought close to a neutral conducting spherical shell then negative charges will be induced on the part of the shell closer to q and equal positive charges will appear on side of the shell farther from q.I understand this part. But if the conducting spherical...
  33. T

    Understanding Quantum Monte Carlo Methods: Clearing up Doubts on Their Use

    Hi, I understood the formal derivation of various QMC methods like Path Integral Monte Carlo. However, at the end of the day I still have a doubt on how to effectively use these techniques. Given that we can interpret \beta in the quantum operator e^{-\beta\hat{H}} both as an inverse...
  34. Y

    What is the voltage produced by standing on a 15 cm quartz crystal?

    Hi, What would be the voltage developed across a Piezo-electric crystal, say Quartz of size 15 cm-length, width and 2 cm thickness, If I stand on it. My weight is around 75 kg :) I have no idea how to calculate it.
  35. A

    An interesting(or very stupid) doubt that came to mind

    I was dealing with the derivation of Stefan's law from Planck's law. In this derivation one gets to the following equation \frac{xe^{x}}{e^{x}-1}=5 At this point most places I looked provide an aproximate numerical solution to this transcendental equation and carry on. But I wwas thinking...
  36. sankalpmittal

    Theoretical doubt regarding capacitance

    I understand that the dielectric constant of a perfect isolated charged conductor is infinite when its placed in an electric field (generally uniform)... Now I also know that when a conductor is placed between a parallel plate capacitor such that the distance between two plates in those...
  37. ShreyasR

    Basic doubt about a concept in Optics

    This may sound really silly but yeah, a plane mirror, and a white sheet of paper, both reflect all the wavelengths of light incident on them. So Instead of a plane mirror, if I use a white sheet of paper, Why don't I see a reflection of myself? I have studied ray diagrams, and i know how an...
  38. F

    Quick doubt about linear application and its matrix

    Homework Statement Let ##f:\mathbb{R}^3\to \mathbb{R}^3## such that ##v_1=(1,0,1) , v_2=(0,1,-1), v_3=(0,0,2)## and ##f(v_1)=(3,1,0), f(v_2)=(-1,0,2), f(v_3)=(0,2,0)## find ##M^{E,E}_f## where ##E=(e_1,e_2,e_3)## is the canonical basis. The Attempt at a Solution i see ##v_1=e_1+e_3##...
  39. K

    Buoyancy Situation Doubt - Archimedes Principle

    Hi to all, i will appreciate your help in this. This is the situation: I have a tank, with a water column in it. This tank at the bottom has an "ideal" seal (a seal that permit the passing of object from bottom to upwards, but not the water to fall down.) In this system i have sphere with...
  40. D

    Was My Prof. Wrong? Temperature & Potency Questions Answered

    1. 2 questions, one asked for the temperature of the water max density and the other one a Potency question which the awnser was 1125... Trying to be funny( hahaha funny as **** ) i wrote 1124,999... as the anwser, since 1124,999...=1125 but my prof. said it was wrong this statement in...
  41. E

    Lenz's Rule - Doubts, Force, and Magnetic Field

    I have certain doubts with Lenz's Law. Now, consider a horizontal loop. If a magnet with N facing the entrance of the loop is moving towards the loop. By Lenz's, Flux has increased. Who has increased it. The magnet. We oppose the downward B by inducing the UPWARD B. Thus, I is clockwise (RHR)...
  42. M

    Doubt Concerning The Selfish Gene

    Doubt Concerning "The Selfish Gene" In the first chapter of "The Selfish Gene", when talking about replicating molecules, Richard Dawkins writes: "Can we reconcile the idea that copying errors are an essential prerequisite for evolution to occur, with the statement that natural selection...
  43. C

    Masters doubt regarding computational neuroscience career

    I'm a biomedical engineering student interested in computational neuroscience, "the neural code" and systems neuroscience to be more concrete. The problem is in my country Mexico, master's degrees either focus in the mathematical side or the biological. What would be better to study a master's...
  44. F

    Doubt about exercise with eigenvalues

    Homework Statement Given the endomorphism ϕ in ##\mathbb{E}^4## such that: ϕ(x,y,z,t)=(4x-3z+3t, 4y-3x-3t,-z+t,z-t) find: A)ker(ϕ) B)Im(ϕ) C)eigenvalues and multiplicities D)eigenspaces E)is ϕ self-adjoint or not? explain The Attempt at a Solution I get the associated matrix...
  45. T

    Can Conservative Forces Be Neglected During Collision Analysis?

    Homework Statement While solving problems ,during collision ,we neglect impulse of external forces like gravitational force , spring force , acting on the system . The cases are 1) An object falling from a height on a pan attached to a vertically hanging massless spring and colliding...
  46. D

    Position of Arms When Facing North

    Hey folks i have a silly doubt ^^ why when someone is in front of you is like this person position of the arms are diferent i mean if someone is in front of you the person arm is left and your is right and where this person right arm is your left arm, and both are directed north ?? thanks for...
  47. M

    Inflationary paradigm in trouble after Planck2013 ? I doubt it, but

    "Inflationary paradigm in trouble after Planck2013"? I doubt it, but.. After all those reports that Planck2013 gave us a picture of the early universe perfectly consistent with a simple form of inflation, slow-roll inflation, now comes a preprint saying that the fine print is problematic...
  48. S

    QM operator and double slit experiment doubt basics

    well i am a starter in QM, i have 2 big doubts ! let me first tell what i understood , there is phsi which defines a state of a system, phsi times x is a position operator and phsi 's derivative of x multiplied by i h is its momentum operator ... well then i operator these in phsi and what do...
  49. D

    Understanding Free Gibbs Energy: The Role of TΔS in Thermodynamics

    I´m having serious problems with free gibbs energy equation. My main problem is that i don't know the meaning of TΔS that appears in free gibbs formula. I know that S is entropy and T temperature; but some books say that TΔS is energy lost or dispersal energy; energy unavailable to do work; but...
  50. dexterdev

    Doubt regarding PLL 565 free running frequency

    Hi PF, I am trying out LM565 PLL IC and designed the basic circuit for checking free running frequency f0 (2.5 KHz). I verified the f0 by not giving any input signal (input pin floating, should I GND it ??) Now the problem is that while sweeping the frequencies up and down the free...
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