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. jaumzaum

    Conceptual Doubts in Eletrodynamics

    I'm having a lot of "simple" conceptual doubts when I try to study eletrodynamics in a qualitative way. Look at the circuit below http://img802.imageshack.us/img802/5349/suidbfhksdbgsdfg.png First we have a capacitor and a generator of voltage V (A). We wait until the capacitor is fully...
  2. P

    Conceptual doubts about capacitors and dipole antennas

    I have some conceptual questions regarding capacitors and dipole antennas. Consider a parallel plate capacitor made with two conducting plates, initially uncharged. If I connect each plate to a different terminal of the battery, charge will start to flow from one plate to another. Consider...
  3. Z

    Doubts regarding 3 question form motion of a particle

    Doubts regarding 3 question form motion of a particle! :) Homework Statement Doubts related to 3 problems..I have uploaded the question up in the attachment. Homework Equations The Attempt at a Solution for question one,the body doesn't come to rest,s is the total dist at any...
  4. C

    Doubts about heisenbergs uncertainty principle.

    Doubts about wave particle duality I know that a wave packet is formed by superposition of several individual waves having different wavelength.And the resultant wave has varying amplitudes.And from these amplitudes we can find the likeliness of the object to be in that position. My doubt is...
  5. C

    Doubts on impulse and momentum

    Homework Statement An antitank missile (m = 12kg.), when it reaches the maximum height (v = 0) explodes breaking into a large piece of 5kg. and a multitude of small pieces exiting vertically upwards with a speed of 40m / s. What is the speed of the first piece?. A locomotive traveling at...
  6. jaumzaum

    Doubts about Ksp, Solubility, Kb - Answered by João

    I'm having some doubts about Ksp, solubility, Kb... 1) If a salt has a solubility of 1g/L, it means that a) there is 1g of the salt itself in aqueous state in the solution or b) there is 1g of salt(aq) + salt ions in solution? 2) The elements of the 2A family makes moderate bases. That's...
  7. jaumzaum

    Some doubts I have while trying to compare boiling points/ solubility

    I was trying to compare some solubilities (in water) and some boiling points, and I could not explain it for some molucules. Also, I have some doubts in the theory itself. Why is 2-pentanone more soluble than pentanoic acid? Why is a ketone more soluble than the respective aldeyde...
  8. N

    Doubts about Computer Engineering

    Hi everyone I'm a new user of this forum ! I wanted to know if a computer engineer has some chance to work into robotics and aerospace industry. What do you think ? And a computer engineer could call himself an electronics engineer ?
  9. S

    Answers to Doubts on -15 as L.C.M., Complex Numbers & More

    I had a few doubts in mind. Please help. 1) Is -15 the L.C.M. of -5 and -3? 2) Can all complex numbers be plotted in a number line. 3) 1^(1/3)= 1, ω, ω^2, where ω= -(1/2)+i[3^(1/2)/2] Then, if we plot these 3 values along a number line, will we get 3 different points or will it...
  10. TrickyDicky

    Some doubts concerning the mathematical bases of GR

    I'm a little confused about certain assumptions usually made in GR as to how rigorous they are mathematically speaking. For instance the assumption generally presented without proof that GR spacetime manifold is a Hausdorff space seems not to be warranted given the fact that pseudometric spaces...
  11. J

    Got doubts about Curiosity surviving Mars landing

    That landing manouever sounds too complicated, too susciptable to errors. But surely they know more than me and feel it's the best way. Still, I think it will fail. That's my prediction. Wasn't there a less error-prone way of setting down on the surface? Maybe though it was a budget issue.
  12. N

    I have few doubts regarding short circuit test of transformers.

    Hi, What does rated output in a transformer signify? Is power same(or almost same) on both sides? In short circuit test, we apply reduced voltage to HV winding so as to circulate rated current in HV. This will cause rated current to flow in LV. But as per definiton of rated current...
  13. A

    I have an doubts in the gravitation law.

    Dear Sir, My name is Ashish R. Sai I am from India.I just appeared for 11th std.A few days ago I went through Gravitation.I completed my assignment.After completing assignments,I tried to find the gravitation between the moon and earth. During this i got a few doubts in this...
  14. J

    Solving Vector Norm with F Matrix: Advice from Jo

    Hi guys Assume F to be a square matrix, say 3 by 3. Now I want to find a vector q (3 by 1) to meet the requirement that norm(F*q)=1. How can I find it? What is the solution in general? THanks in advance! Jo
  15. A

    Differential form of distances and some other doubts

    1) In a lot of instances i see distances and volumes written in the differential form. For instance dV = dxdydz Why not just write it as V = xyz (or any other letters, but not in the differential form)? In the image below, dx seems to be the inital length in x axis, and dy in the y axis...
  16. R

    Speed of Light: Doubts and Confusions

    Hi all One things that puzzles me is the speed of light. We measure it always the same speed independently if we are moving or still. But here is where i get really confused: if we are moving against a light ray (imagine that I will "bump" with the light ray), the speed that we measure is the...
  17. D

    Some doubts regarding rotational dynamics

    a) suppose we tie a ball with a string and rotate it keeping its other end tied with one of our fingers then the only external force acting on it is the tension. Which force then cancells 'mg' acting vertically downward? b) if a mass is rotating in a circular path then in which direction does...
  18. A

    A few doubts about quantum field theory and high energy physics.

    1. I read that the picture of gauge bosons as mediators of interaction originates in and is valid in perturbation theory. But how do we know that picture is correct? We do perturbation theory only because we do not know how to study a system in a fully non-perturbative way. If someday we...
  19. B

    Collision response calculation doubts and issues

    Ok, I've already posted this same question in another forum section but probably it was the wrong one and the post was deleted, according to the rules. My apologies for the big mistake. Sorry. :approve: I try to re-post the same question here, hoping it is the most suited section. I'm...
  20. B

    Collision response calculation doubts and issues

    Hi all, I hope that I'm posting in the right section of the forum. If not, I kindly request a moderator to move the thread to the proper section. Thanks in advance. I'm currently working on a prototype of a 3d simulator in which entities of different shape and mass move possibly colliding...
  21. P

    Relativity of Simultaneity & C Invariance Doubts

    Hi all, I'm trying to understand relativity for the first time. First of all I'm sorry for my bad English, I'll try to be as clear as possible. My doubt is the following: In my books and on many web sites I have red the thought experiment of the train and the two bolts of lightning to explain...
  22. I

    Hi guys, im having some doubts getting this exercise:20,0 g of

    Hi guys, I am having some doubts getting this exercise: 20,0 g of iron (60% purity) are reacted with sulphuric acid (80 % pure) Iron (II) sulphate and hydrogen are formed: Fe + H2SO4 → H2 + FeSO4 1. Which is the limiting reactant? 2. How much Iron (II) sulphate will be obtained? 3...
  23. P

    How can nano-slit arrays affect the focusing of surface plasmons?

    Hey! I am an undergrad student working on my final thesis on surface plasmons. I have the following queries. Any help will be highly appreciated. 1) How far do these plasmons propagate at the interface of the metal and dielectric? 2) Do these plasmons convert the incident TM polarised light...
  24. R

    How does density affect pressure in longitudinal waves?

    In my textbook they have introduced the concept of longitudinal waves and go on to explain what a compression and what a rarefaction is.It is written- "In a compression, there is a temporary increase in the density of the medium; and in a rarefaction,there is a temporary decrease in the density...
  25. R

    Questions About Magnetism: Forces & Flux

    My book says that there is not net magnetic force between two non-magnetic materials. Shouldn't there be a little magnetic force rather than 'no net force' between two non-magnetic substances. Aren't they successful to influence the atomic currents of other to a considerable degree? How is...
  26. R

    Doubts regarding Atomic mass,relative atomic mass and mass number.

    I was reading my science textbook and they have introduced the concepts of atomic mass,relative atomic mass and mass number.Here are some doubts I have- 1)Is atomic mass a ratio ? 2)1/12th of a C-12 atom is half a proton,half a neutron and half an electron.Since mass of an electron is...
  27. R

    Doubts about Gravitation and Force

    My book says r^3/t^2 was found constant by Kepler. What this constant is called? How is acceleration equal to v^2/r in case of circular motion? Why is rate of change of momentum or say product of mass and acceleration equal to force? Why not was it ma^2? How was it proved that it...
  28. U

    Physics Doubts about my own career (physics student)

    Hi everyone, I have posted one or two questions in classical physics, but I'm basically new here. I'm relatively new physics student. I've been studying physics in university about a year by no, although the interest in physics comes from far behind. I'm relatively good at maths, although...
  29. R

    MPPT systems + Solar Panels major doubts

    I'm working in the Power Systems team of CubeSAT. It is concerned with building a small student satellite with dimensions of 10x10cm. Our basic block diagram is as follows Solar panels-> In parallel Shunt Regulator -> Buck Converter->PRU (MAX8934A)->DC-DC Converters->Loads The shunt...
  30. L

    Application of Gauss' law - some doubts

    Application of Gauss' law -- some doubts Homework Statement Revered Members, I have attached images of applications of Gauss' law namely 1) Electric field due to an infinitely long charged wire and 2) Electric field due to an infinite charged plane sheet. In both cases Gaussian surface is...
  31. L

    MS Office 2010 - purchase doubts

    MS Office 2010 -- purchase doubts Dear members, Products like Norton Anti Virus, when bought, is valid for one year or two years depending on the type of purchase and we have to renew the subscription periodically. Whether this applies to MS Office 2010? I plan to buy it. It will be waste of...
  32. A

    Doubts about self-energy, enthelpy of formation and atomic radius

    Hello everybody, I'm not sure if this post is more appropriate here or in the physics section (it's about biophysics topics): if it's off-topic here, please excuse me and move it. I was wondering if it's possible to calculate the enthalpy of formation of a gas molecule, in this example...
  33. I

    Some doubts on signal velocity

    Hi There are several posts here on group velocity, phase velocity and the confusion caused by it. I also read that article posted on mathpages.com (who is the author ?). I have some questions after reading these things. Like that article says, there three kinds of 'speeds' concerning...
  34. H

    Michelson-Morley experiment doubts

    Hello, I am newly learning special relativity. I have this particular doubt> Why is light moving along the hypoteneuse of the triangle while we are moving the apparatus? (Its not like it has a horizontal component of velocity which is equal to the velocity of the apparatus).
  35. S

    Some doubts about my education.

    Good day, I'm a Mexican student who is currently in his 3rd year of Junior High School; from an early age I have shown some inclination towards Mathematics and Science (especially Physics). Within a few months I will finish Junior High School and I'm planning in enrolling in the International...
  36. E

    Doubts about the formula for hydrostatic water pressure on a vertical surface

    Hey guys, So I have just learned that the formula for a fluid's hydrostatic pressure (let's say water for the purpose of simplification) in terms of depth is: P = ρ * g * h Now I have been reading a bit on my textbook and I found out that the derivation of this formula is based on the...
  37. maverick280857

    Transverse Susceptibility, and doubts about retarded/advanced Green's Functions

    Hi, I have been working through lecture notes of a condensed matter field theory class, and unfortunately I haven't found references for some of the specialized calculations though the way they're done makes them seem common knowledge in the cond-mat community. I have started this thread...
  38. L

    Does a Free Particle Have Potential Energy and Kinetic Energy?

    Homework Statement Revered members, A free particle is one which has no forces acting on it and since there is no forces acting on it, so there is no potential energy and E is entirely kinetic. Homework Equations The Attempt at a Solution My doubt is, when no forces act on a...
  39. S

    Am I Cut Out for a Math Major? Experiencing Doubts and Confusion as a Sophomore

    I'm a sophomore math major. I've always liked math, and started college with a double major in chem and math, but now I have decided to drop chem and focus on math. I'm taking calc 3, proofs, and linear algebra ( not the proof-based one) this semester. However, these past days I have had some...
  40. L

    Doppler effect and some doubts

    Homework Statement Revered members, I have attached the image of Doppler effect explanation. Homework Equations I have the following doubts 1)t1 = L/v 2) t2 = T0 +( L + vsT0)/v But why T0 comes here, instead of ( L + vsT0)/v The Attempt at a Solution
  41. F

    OUNT OF HEAT ABSORBED AND GIVEN OUT BY REFRIGERANT IN HEAT PUMP

    let's say some amount of heat is absorbed by a refrigerant for phase change at a low pressure. will this heat absorbed be equal to the heat given out by the compressed refrigerant at high pressure? i know that the amount of heat required for phase change from liquid to vapour is less at low...
  42. F

    Does Pressure Affect Heat Absorption and Release in Heat Pumps?

    let's say some amount of heat is absorbed by a refrigerant for phase change at a low pressure. will this heat absorbed be equal to the heat given out by the compressed refrigerant at high pressure? i know that the amount of heat required for phase change from liquid to vapour is less at low...
  43. L

    Electron as a wave - some doubts

    electron as a wave -- some doubts Homework Statement While dealing with deBroglie's idea, my book mentions these points 1) The electron is a wave whose length decreases with energy 2) If you try to squash an electron wave closer to the nucleus, the wavelength must get smaller 3) When...
  44. L

    X ray production - doubts in the principle involved

    X ray production -- doubts in the principle involved Homework Statement In x ray production, air molecules are ionised due to presence of very high electric field within the tube and positive ions are attracted to the cathode C and due to their impact electrons are emitted from the cathode...
  45. M

    Doubts on the Vitali Set - Marco's Story

    Hello all, I have a doubt on the Vitali set. In its construction we define equivalence classes, two numbers belonging to one if their difference is rational. Then we "pick" a member per class, forming a set. It is then shown that the interval [0,1] is a disjoint union of such set (after a...
  46. A

    Programs Choosing a Minor in Physics: Mathematics or Chemistry? Get Expert Advice

    Hi there, I've completed my first year studying physics an now I have to choose a minor. I'm down to choosing between mathematics and chemistry, and I hope to get some advice from you guys. The reason I'd study chemistry is because it's interesting, it blends quite well with physics (or so...
  47. H

    Why Does Charge Flow to Outer Spherical Shell?

    So there are two concentric conducting spherical shells one with radius R and another 2R with charge +Q and +2Q respectively... Now the two are connected by a conducting wire. Why does the entire charge flow to the outer shell? Please clarify my doubts. I will be grateful.
  48. S

    Gyroscope doubts. Please answer

    Gyroscope doubts. Please answer :) Consider the case of a common demonstration which you would find in videos. A bicycle wheel mounted on a shaft is set into rotation, axis is made horizontal and the shaft stays horizontal for sometime and eventually goes down as the wheel spin slows down due...
  49. S

    Gyroscope doubts. Please answer

    Gyroscope doubts. Please answer :) Consider the case of a common demonstration which you would find in videos. A bicycle wheel mounted on a shaft is set into rotation, axis is made horizontal and the shaft stays horizontal for sometime and eventually goes down as the wheel spin slows down due...
  50. E

    Is Reactive Power Useful? When Should It Be Minimized?

    Yes I understand the definition of reactive power. It is the power that flows back and forth on transmission lines and does not do work(correct me). My question is, is reactive power useful? In what case reactive power has to be minimized as low as possible? I read an article about the...
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