Concept Definition and 1000 Threads

I went to a bar last night that had recently re-opened. From the entry area to the service station, all the seats were occupied, and people were standing near the occupants, but past the service station, the bar was completely unoccupied, and there was a sign: Detail: I didn't want to take...

I found this video on youtube which is trying to explain Fourier transform using the center of mass concept At 15:20 the expression of the x coordinate is given in the video. I believe it is wrong, and it should be: ##\frac{{\int g(t)e^{(-2 \pi ift)}.g(t).2 \pi f.dt}} { \int g(t).2 \pi...

I have a been using a very efficient rat trap. I catch many rats in it as it appeals to their curiosity about smells and ignorance about magnets. It is a walk-the plank rat trap. There are more than 30 rat trap ideas but this one is good because of its simplicity. I got my idea from this man's...

--no explanation as conceptual error--

I am currently reading Foster and Nightingale and when it comes to the concept of parallel transport, the authors don't go very deep in explaining it except just stating that if a vector is subject to parallel transport along a parameterized curve, there is no change in its length or direction...

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I have been trying to understand it but I couldn't can anyone illustrate with deeper answer?

I'm studying Core Principles of Special and General Relativity by Luscombe. In the section on Bondi's ##k##-factor, it says: I want to clarify if my derivation of the above claim is correct. The image on the left is what's included in the text and referred to by the above paragraph. I made...

My answer seems to be way-off/improbable, so I figured something is wrong with it. From the periodic table, Mr of tetraethyl orthosilicate = 208.33 Mr of ethanol = 46.069 Mr of water = 18.015 Mr of SiO2 = 60.084 Let the volume of tetraethyl orthosilicate, ethanol and water be x,y,z ml...

Hi everyone! I ask some help in understanding better the concept of voltage. The voltage is a difference in electric potential between two points ##a## and ##b##. It is defined as However, I'm a bit confused with the use of notation: - Is ##V_{ab}## the same as ##\Delta{V}##, or rather...

The reference in the summary refers to an article which has been recently accepted by The Astrophysical Journal. A draft version of the article dated December 10, 2019 is https://arxiv.org/pdf/1912.04903.pdf . The content of the draft article is way over my head, so I am hoping that...

Hello all I am trying to better understand the concept of Energy and i was hoping some could help clear a few things up. I have a car that is pushing a box with a force of 10N. The car pushes the box 63 meters as shown below:- I know that the energy which is the capacity to do work is...

if I shoot the football, the ball will recive a force in specific direction, and it would follow that direction. Does the work is done by me when I shooted the ball, or the ball does work when it moves all the period after my shooting ? the work includes force and displacement , so who does the...

Hello all I was wondering if some could help me understand the concept of Axial Loading/Force. From research Axial loading can be defined as a load that passes through the centre of gravity of a members cross section, this causes either compression or tension. The bit I don't fully understand...

Michio Kaku and Lawrence Krauss are both well-renowned physicists who propose that the universe (or universes) was generated out of nothing. Krauss, in his book "A Universe from Nothing" argued that the universe was probably created by a primordial "nothingness" with no space and time and...

Summary: If I could spontaneously shift an element's atomic number down by one, what kind of reactions could I cause? What would happen if a handful of O2 just transformed into N2? <mentor: thread moved to SF & f forum > Hello, I'm working on developing a chemistry-grounded Dungeons and...

The examples of "formal" power series and polynomials in one indeterminate are familiar and useful in algebra. However, I don't recall the example of rational functions (ratios of polynomials) in one indeterminate being used for anything. Is that concept useful? - or trivial? -or equivalent...

Hello all; I am trying to better understand the idea of Moments. I know how to calculate moments i.e. Distance * Perpendicular Force. My understanding was that moments were any push/pull force that creates a turning action about some point - that is what a moment is to me, I have shown this...

Answer choices: N2L for Translation, N2L for Rotation, Both, Either1. You are asked to find the angular acceleration of a low-friction pulley with a given force exerted on it. My solution = N2L for rotation 2. You are asked to find the angular acceleration of a low-friction pulley due to a...

Hello all: I have a small question about nuclear propulsion , why everyone are trying to use it ,and why this wired choice of nuclear option , retrofitting a nuclear reactor to mount it on the rocket , isn't that a little dangerous , why they don't use other option or research it , there is few...

[Edit 23.12.2019: A much extended, polished version of my contributions to this thread can be found in my paper Born's rule and measurement (arXiv:1912.09906).] Well, it is simpler than to introduce in full generality Born's rule. Everything can be motivated and introduced nicely for a qubit...

Summary: In the past, physicists talked of the phenomenon of "wave function collapse" very freely, whereas now there seems to be some reservation about it. Why? In reading older popular physics literature, physicists used to talk about "wave function collapse" freely and more often...

Hi all. I'll get to the point. I've been interested in electricity since I was in college. Concepts such as current and resistance seemed easy to grasp for me but voltage remains a little bit obscure. It's thanks to this forum (specially forum members Jim Hardy r.i.p and SophieCentaur, sorry if...

If ##v## is an element of a vector space ##V## and for example ##\mathcal{B}=\{e_1,e_2,e_3\}## is a basis of ##V##, then, at least, there should be another basis for ##V## in which the vectors of ##\mathcal{B}## can be expressed, but at the same time, the vectors of this other basis must also be...

can anyone explain why the voltage reading is negative for the resistor over a time period , yet the capacitor reading always stays positive ? In AC generation the voltages goes from negative to positive, how exactly does this affect the circuit components voltages? I am not sure how AC affects...

should n't it be a maximum number to achieve less than 0.5% uncertainty for the last question as you add more disks would there not be more uncertanity therefore as the number of disks for 0.5% is 9.5, 10 would give an unceranity of greater than 0.5% so it should be 9? the answer is 10.

This is the official thread for my scifi project Blood Moon (running name, likely to change) **Since my earlier thread got moved here, I might as use this new thread as a starting point for the whole project, and limit usage of the other threads for more specific inquiries about certain...

I am not sure in which direction this induced current would be I am assuming you have to use the dynmo rule or the right hand rule as this is the induced current, and the soft iorn core will cause a force to be produced in the coil which causes the current. If so in which direction would the...

Do we really need concept of cross product at all? I always believed cross product to be sort of simplification of exterior product concept tailored for the 3D case. However, recently I encountered the following sentence «...but, unlike the cross product, the exterior product is associative»...

Not sure where best to post. Local paper has had a couple of articles about the black hole image over the past couple of days. They quote Walter Isaacson “Einstein did not believe, then or later, that these results actually corresponded to anything real,” . Is that true? I couldn't imagine...

Hello! I'm in the early process of brainstorming plans for a roof mounted mobile solar array as a DIY project. The host vehicle will be a 8.5'x20' cargo trailer. On the roof I can fit an array of 6x solar panels that is almost exactly 8.5x20. However, I actually want to create 3 such arrays...

Dear all, I've been reading and got confused of the concept below have two questions question 1) For <ψ|HA|ψ> = <Hψ|A|ψ>, why does the Hamiltonian operator acting on the bra state and <ψ|AH|ψ> in this configuration it will act on the ket state? question 2) what does it mean for H|ψ> = |Hψ>...

Hi, I'm wondering if it is possible to measure radii of stars using general relativity, given its explanation of gravity as curvature of space. Thank you

Supposedly, infininity has been purged from mathematics. Both the infinitely small and the infinitely large have been replaced by the idea of a "limit." For example, a series x0+x1+x3+... is not considered to be a literal infinite sum with infinite terms but only the limiting value of an...

x^2+16x+? That ? Can only be 64 so the polynomial can transform into (x+8)^2 where the position where in this case “8” is must be an integer. What exactly are these kind of concepts called?

if I apply a force constant F=100N en ##y## direction to a body of mass 2kg, it is elevated 3m and I know that the force of gravity is in ##y## direction too. What is the work that I did? I think: ##W_{me}=(F_{me}-F_{g})\times 3## it is correct? and the work made by gravity is "0".

Homework Statement A box of mass X kg hangs motionless from two ropes, as shown in the diagram. The angle of rope 1 is specified amount of degrees. Choose the box as the system. The x-axis runs to the right, the y-axis runs up, and the z-axis is out of the page. What is the magnitude of |F2|...

Homework Statement All context is given here. I am trying to understand a few things about what Morin is doing. 1) How is proving that f(x) is a linear function, which I understand the proof of, relevant to the claim that the torques at the left end cancel? Also, the introduction of the...

1. v = u + at 2. x = ut + 1/2 at^2 3. u^2 = + 2ax Can I use three equeations above for the same concept 'constant accelaration' interchangeablly?

In Hilbert infinity hotel, all the rooms were occupied. Then how did the occupant were able to shift to their adjoining room?? Here I understand, by full mean, ALL the infinite room has a corresponding occupant. I also understand some infinity number are greater because it can be proove when...

Homework Statement 30 litres of N2 and 30 litres of H2 are taken in Habers process with 50% yield.What is the final composition of the compunds in litres? Homework Equations N2+3H2->2NH3 The Attempt at a Solution N2 + 3H2-> 2NH3 intial: 30 30 0 final: 30 - x/2 30-(3x)/2 (2x)/2 so, 30 - x/2 +...

I have seen two approaches to the method of integration by substitution (in two different books). On searching the internet i came to know that Approach I is known as the method of integration by direct substitution whereas Approach II is known as the method of integration by indirect...

What would the theoretical maximum possible speed be for a platform on a horizontal air-bearing (friction-less), if the only propulsion was a spring powered machine gun with unlimited steel balls? The balls go one way, the platform moves proportionally in the opposite direction. Ignore inertia...

What is the best site to learn physics concepts with lots of examples? some site which doesn't show up on google. Like i give example of cplusplus.com which has all topics of c++ programs. Is there some physics site like that? Like i am always confused with pulley,strings, tension problems.

so the concept of work I've never really understood (even after a year and a half of physics classes rip). What mainly confuses me is when the work done is positive or negative. From what I understand the net work=deltaKE or net work=-PE assuming energy is conserved (so if an external force was...

This question came up in another thread. I will post again the link to Nick Herbert's proof here: https://www.physicsforums.com/threads/a-simple-proof-of-bells-theorem.417173/#post-2817138 I don't see where the probability shows up in Nick Herbert's proof. For discussion of Eberhard's proof I...

My professor never really went over this concept clearly in Advanced Calculus. The definition of an equivalent metric from my lecture slides: Two metrics: d1 and d2 on a metric space X are called equivalent when there exists M >= 1 such that M-1d1(x,y) <= d2(x,y) <= Md2(x,y) I am trying to...

In the masterpiece "Philosophiae Naturalis Principia Mathematica" , Newton says: "Absolute, true, and mathematical time, of itself, and from its own nature, flows equably without relation to anything external, and by another name is called duration: relative, apparent, and common time, is some...

https://www.physicsforums.com/attachments/221718 Say if we have two particles P, and Q, traveling at velocities Vp and Vq respectively. If it is IMPOSSIBLE for Q to collide with P, let us find the distance of closest approach. So from the frame of reference of P, itself is stationary, and Q is...

Consider the following examples: 1) combine a spin 1/2 state (with 2D Hilbert space and three spin 0 states (each with 1D Hilbert space). The resultant state is in 3D Hilbert space. 2) combine the same spin 1/2 state (with 2D Hilbert space and one spin 0 state. The states in (1) and (2)...