# What is Doubt: Definition and 591 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. ### I Derivation of the Work done by spring force -- why do we substitute the force magnitude?

i'm copying from the book... Hookes Law - F = -kx W = Fdcos∅ since ∅ is 180°, W = -Fd = -Fx W = ∫(-Fxdx) now the book says, from Hookes Law equation "the force magnitude F is kx. Thus, substitution leads to W = ∫(-kxdx)" why are they saying to substitute the magnitude of the force and not the...
2. ### I Doubt about variable mass systems

Speaking of variable mass systems... it seems to me that there is a flaw in Halliday's reasoning when he talks about this subject. But the formula he derives seems to work to me! He starts with a system of points of total mass \ M and cm velocity \ v. Due to the action of external forces after...
3. ### Doubt on solubility and how to predict it

Two substances are known to be miscible when the intermolecular interactions formed between the molecules of one substance are equal to those formed between the molecules of the other substance. That said, why is benzoic acid, which is predominantly apolar, so it mainly forms London...
4. ### I A doubt about the multiplicity of polynomials in two variables

Let ##P(x,y)## be a multivariable polynomial equation given by $$P(x,y)=52+50x^{2}-20x(1+12y)+8y(31+61y)+(1+2y)(-120+124+488y)=0,$$ which is zero at ##q=\left(-1, -\frac{1}{2}\right)##. That is to say, $$P(q)=P\left(-1, -\frac{1}{2}\right)=0.$$ My doubts relie on the multiplicity of this point...
5. ### Big doubt about graphene in batteries

Well people i'm looking electric Motorcycles. And the same seller it's selling a 72V50Ah battery and a 72V60Ah battery, both IN THE SAME WEIGHT, every battery in the shop occurs the same. So or we have a factory mistake, scam, witchery .....or...graphene in the lithium. I have been reading that...
6. ### Doubt about solution -- Two masses connected by a rod moving on a surface

The doubt is about this question. Which the answer is They say that all the forces are pulling forces? How is this the case? How would this setup even work? I don't think block 2 could pull the rod.
7. ### I Discrete mathematics--An easy doubt on the notations of sums

I have a doubt about the notation and alternative ways to represent the terms involved in sums. Suppose that we have the following multivariable function, $$f(x,y)=\sum^{m}_{j=0}y^{j}\sum^{j-m}_{i=0}x^{i+j}$$. Now, let ##\psi_{j}(x)=\sum^{j-m}_{i=0}x^{i+j}##. In the light of the foregoing, is...
8. ### B Photon Emission: Classical vs Nuclear Fusion

In classical physics we know photon emits when electron move from higher to lower state but in nuclear fusion photon emits when neutron turn into proton. Is both correct?
9. ### Doubt regarding the series ##\sum [\sqrt{n+1} - \sqrt{n}\,]##

We're given the series ##\sum_{n=1}^{\infty} [ \sqrt{n+1} - \sqrt{n} ]##. ##s_n = \sqrt{n+1} - 1## ##s_n## is, of course, an increasing sequence, and unbounded, given any ##M \gt 0##, we have ##N = M^2 +2M## such that ##n \gt N \implies s_n \gt M##. Thus, the series must be divergent. But...
10. ### B Doubt regarding the terms used in the solution

In the solution, the term Lcm and Icm is used. Explain the meaning of these terms? I think cm stands for centre of mass. why that is used in the subscript?does the term angular momentum from the centre of mass of the sphere makes sense? Is the term Lcm and Icm stand for angular momentum of the...
11. ### I Doubt on Morse potential and harmonic oscillator

I have a little doubt about Morse potential used for vibration levels of diatomic molecules. With regard to the image below, if the diatomic molecule is in the vibrational ground state, when the oscillation reaches the maximum amplitude for that state the velocity of the molecule must be zero so...
12. ### Comp Sci For which of the following purposes is the Banker’s algorithm used?

I am new to the operating system and I want to know, Is it right Banker's Algorithm is mainly used to prevent deadlock? I picked this question from https://www.interviewbit.com/operating-system-mcq/ and I think it is also used for Solving deadlock, Can anyone know, Is this right?

49. ### Doubt about vector acceleration

Say... A ball is moving to the right, and we want to say that it doesn't slip. My doubt is, in which case we put Vrot = - Vcm = - α*r or Vrot = Vcm = α * r
50. ### Doubt about the elliptic orbits of the planets

I was thinking to myself, if it were ask to me why is the orbit of planets elliptic, how to justify?: The bould phrases i just know to justify with collected dates. IS this a reasonable justification?