What is Doubts: Definition and 203 Discussions

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. L

    Lenz's law - some doubts in this

    Lenz's law -- some doubts in this Homework Statement Dear members, Please refer my attachment lenz law When the bar magnet with its N-pole is moved towards the coil, the induced current produced in coil S opposes the motion of magnet. It will happen so, if the induced current in the coil S...
  2. L

    Understanding Domain Structure in Ferromagnetic Substances

    Homework Statement Dear Members, Diamagnetic substances acquire magnetism due to orbital motion of electrons paramagnetic substances acquire magnetism due to interaction between magnetic dipoles Ferromagnetic substances acquire magnetism due to domain structure. This is what my...
  3. S

    Physics 11 Significant Figures Doubts

    1) Which is right? 65m/s x 3.2 s = 208 m or 65m/s x 3.2 s = 2.1 x 10^1 m2) is 210 - 3 s.f. or 2 s.f. ? 3) my teacher uses the question as a guide for s.f., is that correct? e.g. A projectile is fired with an initial speed of 1.12 s at a...
  4. A

    Letter from WWI: Larry Doubts its Authenticity

    Harry showed a letter to Larry and told him that it was written by his great grandfather who fought in world war I. The letter was as follows: "Dear Agatha, World War I is finally over. I am coming back home very soon. You would be happy to know that I am totally fine and healthy. I had missed...
  5. R

    Check Valves: Questions Answered

    http://en.wikipedia.org/wiki/Check_valve from the above wiki link I have understood basic concepts on Check Valves Suppose I Heat a gas ( air ) in a closed vessel. It's temp and pressure increase. As soon as the pressure reaches ( or exceeds??) the cracking pressure , the valve opens and...
  6. Telemachus

    Doubts about the meaning of canonical

    Doubts about the meaning of "canonical" Homework Statement Hi there. I have a doubt about what we are talking about when we ask, in linear algebra, for the canonical form of a conic. The doubt is basically, if for example, the canonical form of a circle includes a circle translated at any...
  7. Z

    Confused About Hydroxy Butanoic Acids and Amide Hydrolysis: Can Someone Explain?

    1) My book says that we can distinguish between 2 hydroxy butanoic acid (A) and 3 hydroxy butanoic acid (B) by haloform tests. It says that B gives positive haloform test. I am fine with it. I don't get why A doesnot give positive test as it is also a sec. alcohol . 2)In the base-catalysed...
  8. Z

    Proving Monotonicity for Logarithmic and Fractional Functions?

    Homework Statement I have 2 questions- 1) If x>0, show that log(1+x) < x 2) Is the function f(x) = {x} where {.} denotes fractional part of x increasing on [5,6] ? A1) My book says that we have to construct a function f(x) = x-log(1+x) ans show that it is increasing and f(0)=0 or...
  9. Telemachus

    Double Integral Doubts: Understanding Regions and Order

    Homework Statement Hi there, I've got this doubt about a double integral. I have this region: \displaystyle\int_{-1}^{2}\displaystyle\int_{-\sqrt[ ]{4-x^2}}^{1-x^2}f(x,y)dydx And the thing is, how this region would look like? Would it look like this?: The thing is that after the cut...
  10. R

    What does the UNIX cat command do and how can I access hidden files?

    UNIX “cat” command doubts! I’n new to UNIX so please bear with me. I wanted to know what does the cat file1.txt << file2.txt command do? it doesn’t give an error, just goes accepts the keyboard as stdinput, and on ctrl+d, contents of file1 nor file2 changes. Also one more thing in the...
  11. P

    Some doubts understanding wave nature experiment for electrons

    hello everybody, I'm new here and new to the field of QM also. I have a few doubts regarding the double slit experiment. I know that there are other threads also here about the same thing, and you must be fed up seeing another one pop again, but I'm less brainy than those guys and have more than...
  12. L

    Bohr's atom model. some doubts

    Homework Statement revered members, one limitation of bohr atom model is that it could not account for distribution and arrangement of electrons. i could not understand this statement, that is, according to bohr , electrons revolve around the nucleus in circular orbits and the necessary...
  13. TrickyDicky

    Exploring Geodesics: Understanding Curved Paths in Outer Space

    Let's imagine a test particle in outer space not being subjected to any significant force, gravitational(far enough from any massive object) or any other. Its path would be describing a geodesic that follows the universe curvature, right? Would that be an euclidean straight path, or would it...
  14. P

    Doubts about Einstein Field Equations

    Why should we trust the Reissner–Nordström solution of charged black holes? It relies on coupling between Einstein tensor and EM stress-energy tensor, which has NO experimental support whatsoever. Is there any chance we can test this?
  15. T

    Some calculus exercises doubts

    Homework Statement Problem 1 Find the equation of the tangent line on the following points of the curve. f(x) = \frac{1}{x - a}, a \in \mathbb{R} - \left \{ -2; 4 \} \right; x = -2, x = 4 Problem 2 Find the equation of the line normal to the tangent line on the following points of the curve...
  16. S

    Doubts regarding conversion of mechanical work to heat

    I have problems understanding WHEN mechanical work will be converted to heat . If a body moves , will there always be a rise in temperature , even if negligible ? If not , then read this Problem I recently came across , with the solution too : " From what height must a mass of ice be...
  17. S

    Layman's doubts about Gen Relativity

    1) Is the space-time curvature absolute? For example is the space-time curvature caused by earth(for scientists on Earth) same when viewed from the moon? 2)Does the frequency change of a photon at a point in the gravitational field depends upon its initial position of emission? 3)When...
  18. D

    AC Circuit Qs: Power & Current w/ 200V RMS

    Now this is not a homework question, just a practise question and my answer doesn't match. An AC source of 200 V rms supplies active power of 600 W and reactive power of 800 VAR. The rms current drawn from the source is ? (the answer is 3.75 while mine is 5) I did was squared and added the...
  19. R

    Understanding Light as Wave Doubts

    Doubts from "light as wave" Hi all I am a undergrad and in a week or so i || be performing basic solid state and optics experiments. I want u to clear my following doubts. 1. when we say that a light-wave can be written as A(x,y,z) exp(ikxx + kyy + kzz). What does it mean? I mean to ask...
  20. S

    Solving Transistor Doubts with ADS: 2SD2216 from Panasonic

    Hello all, I have been trying to simulate a circuitry involving a transistor for the microphone line. I believe it was used for amplication of the external audio signal (not too sure, maybe can share the circuit). I am using the ADS to simulate my circuit. The problem I faced was the...
  21. A

    Nagging Doubts just won't go away(song)

    I think time is seriously flawed. I can't get my head around time as a real dimension and curving of time by gravity quantifies things for us, but in a limiting way. What if we look at it this way: a) we are not actually seeing into the past when we observe light from afar, we are just simply...
  22. C

    Doubts on Skin effect & Electricity

    Hi all! This is my first post :D I came across skin effect which blocks propagation of an em-wave within a conductor... But doesn't the energy generated at an electric plant reach our house through conductors flowing for over a 1000 miles sometimes? If I have to consider it just as an...
  23. S

    Doubts about moment of inertia

    Homework Statement The polar ice caps contain about 2.3*10^19 kg of ice. This mass contributes essentially nothing to the moment of inertia of Earth because it is located at the poles, close to the axis of rotation. Because of Global warming, all the ice has melted and formed a uniform coat of...
  24. S

    Am I a physicist? (switched from engineering to physics, experiencing doubts)

    Hi everyone, I'm currently in the 2nd year of my undergraduate studies at the University of Toronto. I've had a pretty confusing career path and I hope you hear me out. For the first year of my undergraduate life, I was in http://engsci.utoronto.ca/" . For those who haven't heard of it, they...
  25. H

    Understanding Dirac Delta Squares: Clarifying Doubts

    hi, may someone help me to clarify my doubts... in my work, i encounter diracdelta square \delta(x-x_1)\delta(x-x_2) i am not sure what it means... it seems if i integrate it \int dx \;\delta(x-x_1)\delta(x-x_2) = \delta(x_1-x_2) is either zero of infinity. is this correct? thanks
  26. E

    Physics Some doubts about medical physics

    I've been seriously considering going to grad school for medical physics for past couple of months. During that time, I've read some posts on the internet and visited the medical physics department at a local hospital a number of times. Based on my admittedly limited experience, I've found the...
  27. A

    Solving Formulas with Odd/Even Conditions - Math Homework

    Homework Equations integral 0 to pi/2 ((cos^n)x dx), integral 0 to pi/2 ((sin^m)x dx), integral 0 to pi/2 ((sin^m)x * (cos^n)x dx), condition: when m,n odd; m,n even , m even n odd n so on... The Attempt at a Solution ans hints: (m-1)/(m+n) * (m-3)/(m+n-2) ....
  28. N

    Solving Euler Theorem Doubts with Partial Derivatives

    firstly, all d's i use will mean partial derivative 'do' because i don't have the font installed. sorry :( please help me with these.. u got to use euler theorem 1. if z= xf(y/x) + g(y/x), show that x2(d2z/dx2) + 2xy(d2z/dxdy) + y2(d2z/dy2) =0 2. if z= (xy)/(x-y), PT (d2z/dx2) + 2(d2z/dxdy)...
  29. T

    Mechanics problem. Please clear my doubts regarding forces.

    Homework Statement In the flgure below, the incline has mass M and is fastened to the stationary horizontal tabletop. The block of mass m is placed near the bottom of the incline and is released with a quick push that sets it sliding upward. It stops near the top of the incline, as shown in the...
  30. baywax

    Can Telescopes Show Moon Landing Evidence?

    Couldn't we just point some high powered telescopes at the moon and show these skeptics the equipment, tire tracks and footprints left behind on the moon by all the missions that went there? Has anyone done that and is there a link to the evidence? Oh... Here's one answer... :redface:
  31. A

    Doubts about change of variable in ODE

    I was trying to check some calculations from a paper myself and I got stuck at a differential equation. Can anybody help me with suggestions? I am giving a simpler version of the differential eqn by setting all numerical constants=1. Consider...
  32. R

    What Are the Fundamental Queries About Classical Physics Concepts?

    1.is work done the dot product of force with displacement of the center of mass of the body or the point of application of the force?? 2.consider a battery whose terminals are connected by a pure conducting wire then since there can be no potential difference between any 2 points on...
  33. T

    Schools First semester of grad school down, having some doubts.

    Hello everyone! I just finished my first semester of graduate school in physics, and I have been struggling with some serious doubts since virtually the first day. During my time as an undergraduate, things were fairly easy for me. Most of my peers were spending 8 hours per day studying and...
  34. K

    What are the other state functions and how do we determine them?

    actually i know some fundamental state function such that temperature, pressure, and volume. But it's because these are the most used. Now my problem is how to know the other state function i.e what are the conditions?
  35. J

    Doubts in double slit experiment

    hi all...it is said that constructive interference happens when the path difference is nlambda and i think wavelength,frequency and amplitude of light going through both slits is the same then why is the central maxima is the brightest spot? why the brightness decreases when n increases...
  36. R

    How does buoyant force relate to weight and pressure?

    1.A rectangular vessel of volume 100 cm * 60 cm * 200 cm is completelyfilled with a water. Neglecting atmospheric pressure: find the net force experienced by a metal foil placed at depth of 5 cm from the free surface. Why ist it 0? 2.If a cuboid is placed at some depth in water. My book...
  37. R

    Questions on Fluids, Gravity, Inertia, and Friction

    My doubts: 1. Why doesn't the time period of a simple pendulum depend either on mass or on the magnitude of amplitude? 2.Why is pressure regardeed as a scalar quantity? I can't say anything about the first question. But about the second I'll share my views. Pressure = Force/ Area : Force...
  38. R

    Questions I have doubts about which came in my olympiad.

    1. Polishing of the surfaces in contact beyond a limit increases friction because: i)irregularities are increased ii)surface projections are sharpened iii)area of actual contact is increased iv)none of these My ans. (ii) 2. A chain is placed on a frictionless table such that 1/5 part is...
  39. D

    Doubts about 0.999 being equal to 1

    If anyone has any further doubts about 0.999... being equal to 1, please direct your attention to today's http://en.wikipedia.org/wiki/0.999..." .
  40. S

    Solving Electric Fields with Gauss's Law: Doubts and Calculations

    Hello, everyone. I have a problem that I solved using Gauss's Law. However, I am unconfident in my answers, as I have very little experience with Gauss's Law. The surfaces of two large (i.e. infinite) parallel conducting plates have charge densities as follows: \sigma_1 on the top of the top...
  41. A

    Doubts in modern physics photoelectric :mad: effect

    i know theses qns may look lame but my answers are not matching with the book .pls help as i have a MAJOR EXAM coming up tomorrow:eek: 1.three photons are coming out from an excited ample of hydrogen atoms with energies of 12.1 10.2 and 1.9 eV respectively then which of the following is...
  42. E

    Doubts whether my integral is right

    Hi, can someone please quickly help me check if I've made a correct attempt at the following question. I'm having doubts whether my integral is right or not because I tried integrating it and applying the limits, but I didn't get the given answer 15/8. Can someone help? thank you...
  43. O

    Time dilation and space contriction doubts

    Hi, I've been with this question in my mind for ages, can somebody, please explain me, if I'm wrong ,and where I'm wrong in my thought's: -If, the length of any object in a moving frame will appear foreshortened in the direction of motion, or contracted. -And a clock in a gravitational...
  44. P

    Solving Limits and Convergence: Doubts and Calculations Explained

    Hi, Today i had a test, and i was wondering if what i did is correct: I had to tell if the :lim_{(x,y) \rightarrow (0,0)} \frac {x*y} {|x|+|y|} exists. What i did was to say lim_{(x,y) \rightarrow (0,0)} \frac {x*y} {|x|+|y|}=lim_{(x,y) \rightarrow (0,0)} \frac {x} {|x|+|y|}*y=0 because it is...
  45. G

    General Doubts about Space Time

    Here are a few questions about space-time. 1. Mass is directly proportional to curve/dent in s-t. (space-time). What is the constant of proportionality? So, by 1kg. mass how much of a curve is produced? OR by how much mass does the pit deepen by 1 unit length? 2. By critical velocity and...
  46. D

    Basic Doubts on BAR MAGNETISM & Magnetic Reversals

    OK ..actually i don't have any doubts generally but when I do some new chapters, i do have some. I was reading about BAR MAGNETISM and about para,dia and ferro properties of materials. My first doubt: 1)How can "angle of dip" at the poles be 90 degrees? .. I think at the South Or North...
  47. P

    Questions and Doubts about the Big-bang

    Taken from http://http://ssscott.tripod.com/BigBang.html Einstein's Theory of Special Relativity says that an object traveling at the speed of light will go into the future, and an object traveling at speeds more than the speed of light will go back into the past. Is this correct? Why...
  48. siddharth

    Doubts in Differential equations

    If I have a second order differential equation (like in SHM) ,ie, (d^2x)/(dt^2)=-kx, (1) the solution is of the form Acos(wt+B) (2). This is obviously true because by substituting i get the result. But the answer could very well have been [-(kx^3)/6 +AX^2+BX + C]. Why do we not take this...
  49. T

    Doubts and Unease: Physics Articles Troubling Ben

    I'd like to preface this by saying that I have limited knowledge in physics, and have not even studied it to degree level yet. But still, bare with me. I have recently found that I find myself with growing unease whilst browsing the Internet or through my weekly New Scientist subscription...
  50. marcus

    Doubts about the z = 10 galaxy of Roser Pello

    several months back some PF people were discussing the finding of a z = 10 galaxy by a French team led by Roser Pello Now three Anglo-Saxons at the Imperial College have reluctantly expressed doubts: they have tried to find the reported Lyman Alpha line and did not see it. S. J...
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