Confusion Definition and 1000 Threads

Homework Statement A spherical ball of mass M and radius r rolls without slipping in a cylindrical of radius R .Find the time period of small oscillations .Homework EquationsThe Attempt at a Solution Please have a look at the picture attached . The ball moves to the right and upward, and...

Hi, The reflection coefficient (R) of an EM wave is, as far as I know, 1 if there is total reflection and -1 if there is total reflection AND the phase changes by 180º. However, we also know that the transmission coefficient is given by T = R + 1 (or by its own formula, which should give the...

http://postimg.org/image/pb0eu3ap3/ So I've got this graph, and magnitude, M, depends on the number of points, N,... but it shouldn't. http://postimg.org/image/pb0eu3ap3/ The line of best fit is... M = a*N ^b It's been a while since I studied, but knowing their relationship would it be...

Shouldn't it be Pdc = 22kN rather than Pcd? I mean the 22kN force arrow is pointing towards C? Because Pdc means the P from D to C no?

Hi everybody, I'm learning Special Relativity, and probably ok with four vectors, the metric equation, the Lorentz Transform, and the Doppler shift, etc., but enough about me. I'm still a little confused about time dilation. In several hypothetical examples of SR that I have seen, two...

I am afraid that I won't get good rank in engineering entrance exam. I have an option of second attempt but I will get distracted easily. So the next option is a BSc. What kind of jobs will I be able to do if I follow this path: BSc->MSc? Or should I sit and study another year for this path:B...

Hello everyone. This is my first post on these forums. I came here for guidance, as I am currently very confused with the nature of reality, and how I should be thinking. I can't imagine that anyone here will have an absolute answer, but I am hoping to be grounded a little. The biggest problem...

Is Poincare' Recurrence Theorem (PCRT) considered a possible explanation for the "low entropy" initial conditions of the universe? Is the following a roughly correct paraphrasing of it? For a phase space obeying Liouville's theorem (closed, non-compress-able, non-decompress-able), the...

I'm a mechatronics engineering student, and I know that electronics is a requirement in most engineering programs. I'm been dealing with electronics recently and I've been studying electric circuits. I've been noticing that in some of them instead of being closed (in diagrams) they are like...

Homework Statement In position 1, the 0.25kg block is held against the spring, compressing it by 150mm. the block then is released, and the spring fires it up the cylindrical surface. Neglecting friction, find the contact force exerted on the block by the surface in position 2.[/B] 1/2kx^2 -...

Homework Statement This is not a homework question and I am asking this question out of curiosity. We have been taught rectangular wave guides and cavity resonator recently and I don't want to gulp the wave equations as it is, so the problem that I am facing ( I have written it on paper and...

I was reading textbook and felt confused about this-- when trying to deal with inner inductance of transmission line, only the fraction (x/r)^2 of total current, which interlock with magnetic lines should be considered. However, isn't the inductance or even flux linkage an intermediate...

If solar eclipse occurs at 12h 12m 12s actually. Then at what time one will see it on earth. Will the speed of light affect the time if moon starts covering sun at 12 h 12 m 12s when one will see covering on earth? at what time? I just want to know I am just curious do you think the time taken...

Hello, I have to estimate some values from a plot (shown in the attachment). The trouble is I'm not sure how to read one of the scales could someone please explain the nature of the scale along the top frame, the angular scale, i.e how it is spaced. One of my aims is to estimate which angle...

I'm coming from a physics background, but find pure mathematics extremely interesting, so have decided to try and gain a more fundamental understanding of the subject. I've recently been reading up on relations and how one can define them as sets of ordered pairs. I am particularly interested in...

I've been reading Wald's book on General Relativity and in chapter 3 he introduces and uses the so-called Hadamard's Lemma: For any smooth (i.e. C^{\infty}) function F: \mathbb{R}^{n}\rightarrow\mathbb{R} and any a=(a^{1},\ldots,a^{n})\in\mathbb{R}^{n} there exist C^{\infty} functions H_{\mu}...

I wasn't sure where to post this, and I hope this is the right place. I've been reading ahead of my lectures, and I've gotten a book that introduces tensors. It very quickly introduces Einstein Summation Convention, which I think I understand, \sum_{i=1}^{3} x_{i} y_{i} = x_{i} y_{i} = x \cdot...

My TI-89 calculator rearranged $$ 2^{2m+1}-1$$ to $$ 2\times 4^m - 1 $$ I can't for life of me work out how it did it. Is anybody able to put me out of my misery? Thank you in advance! Ben

Homework Statement What's the difference between the two equations for a plane? This question is somewhat related to my other, overarching question here: https://www.physicsforums.com/threads/i-am-confused-about-how-multivariable-calc-works.798798/ Homework Equations ## a(x - x_0) + b(y -...

So basically, I am inferring the following based off of what I've learned. When we hook a battery up to a circuit, this creates a potential difference. Say we use a 9V battery. Here is a picture: From what I know, the horizontal is a equipotential surface, and the vertical has different...

Homework Statement In a book discussing a simple electrical circuit it said "If a thick wire is used in the experiment, the current will be extremely high for a very low voltage. The wire can get very hot very quickly". This got me thinking about fuses in plugs. Is the fuse in a plug a thick...

I was studying 2nd law thermodynamics. In that context found the clausius's inequality saying closed integral of dQ/T <0 for irreversible process. And from the reversible process entropy was defined. And from that view they said that for irreversible process dS>dQ/T. Now when I saw some...

Hi, I am kind of confused about how a centrifugal force works. Every where i search there seems to be 2 opinions, that centrifugal force is indeed a force and others that argue that it is not. What I want to understand is in (for example) a centrifuge, which rotates very quickly with a test...

As my computer kept urging me to back up my system onto an external hard drive, I decided I would buy one, but first I needed to find out which size to buy; so I backed up the system on the computer itself to find out how much space it takes up. This created two files (one, WindowsImage, and...

When no current is passed through the coil it shows no deflection i.e. B is in the direction shown. But according to theory both fields should be perpendicular (Earth's horizontal field and the one due to coil). But I am confused because the coil would ideally create a magnetic field that is...

From what I have heard, it is impossible to know the exact position and the exact velocity of any particle, but what I don't get is why. Does one of those values just not exist at any given point, or does measuring one change the other, or is it maybe something completely different?

Hi, I am confused over the potential energy equation. I have been taught that potential energy is MGH M=mass, G=gravity on surface, and H=height from earth. However being on the internet and learning more i have noticed people use GmM/r^2 and i am very confused why it is switched. please help me...

In an effort to clarify my question, allow me first of all to state what I believe I DO understand: All observed elementary particles are either fermions or bosons. Ignoring the Higgs boson (which gives other particles mass via the Higgs mechanism), there are four forces operating in the...

I've a small confusion about formula ##\log^3 n = \log \log \log n## or ##\log^3 n = (\log n)^3 ##

Recently I started seeing integral calculus and right now we are covering the topic of the antiderivative. At first sign it was not very difficult, until we started seeing integral variable substitution. The problem starts right here: Let's suppose that we have a function like this: \int...

Hi! I am in second year of my college. I want to pursue theoretical physics and plan to work on things like String theory and High Energy Physics. Now I was trying to get a summer project in Physics and I have been offered an opportunity to do a project in theoretical Plasma Physics. Is it right...

So, recently I started learning about electronic components and then I started learning about semiconductors. The one which I've been having some real trouble to understand its function is the transistor. So I bought an electronics textbook called El ABC de La Electrónica (The ABC of Electronics...

Ok, so a lot people said that 1. the charge outside of the enclosed surface wouldn't influence the total flux that penetrate the surface 2. q/ε wouldn't change if the charge inside the surface does not change (see my painting, so it can help you understand what i meant) i was ok with these...

Question: A person wants to jump in the air. To do so, he has to crouch a distance C. He then has a push-off phase, where the he accelerates upwards by a distance C. At the end of push-off, he then achieves takeoff (airborne). The end of his takeoff distance is H, and H is the difference between...

The sky is blue because blue light resonates with the air molecules and therefore has a higher scattering intensity (due to Raleigh scattering). Thus, we see blue light when we look at the sky (any light that we see, while not looking directly at the sun, must have been scattered). Is this...

I have quite a hard time understand how these things relate and where i go wrong. I think this fits in better here since what I'm having trouble with is the theory and not a specific exercise problem. So the book I'm using derived this connection between work and potential energy when a...

so what i understand is that packing fraction is mass defect per nucleon. mass defect is the difference between total mass of the nucleons and the actual mass of the nucleus of an atom. if A=mass number [M][/p]=mass of proton [M][/n]=mass of neutron M=mass of nucleus then packing...

Reading up on quarter wave transmission lines and I'm confused about the actual length of the line. Is a quarter wavelength line equal to the length of the incident and reflected wave? Or is it only equal to the length of the incident wave?

Hi all,I am trying to understand relativity and Lorentz Transformation more clearly but I have some problems. Assume that we have frame F' which is moving at velocity v with respect to F. Now assume we have an object, O, moving at velocity, w, with respect to F. Frame F has its own time, t, and...

Homework Statement A rod of mass ##M## and length ##l## is pivoted at the center(##O##) in horizontal position. An object of equal mass(having velocity ##v##) falls vertically on the rod at distance ##\frac{l}{4}## from ##O## and sticks to it. Find the angular velocity of the rod just after...

are operators solely used to find the expectation value of something? What does it mean to use the momentum operator over wavefunction? What does it give? I am guessing it doesn't give momentum since momentum can never be a function of space. How to calculate kinetic energy, given the...

In deriving the pressure of a gas, my book states that 'if all molecules are equally likely to be traveling in any direction, the fraction whose trajectories lie in an elemental solid angle dΩ is dΩ/4π'. This initally made sense to me, but then thinking about it, I wrote dΩ=sinθdθdφ and this...

Hi I was watching a TV program about QM on BBC4 given by Jim Khalili. I am a little confused by two aspects. First, he attempted to draw an analogy about polarisation of entangled particles always being opposite when measured, by using a card game where a dealer deals cards in pairs. I think it...

Homework Statement I was reading the textbook section on angular momentum, and I'm having some difficulty grasping angular momentum. Here is a question: In the book, it says that the angular momentum L is equal to vector r cross vector p for a particle. But, for a rigid body, the equation...

So the basic idea is that the differential operator acting on the vector space V of functions f:[a,b]->ℂ, with some weight function w(x) L≡d/dx[p(x)d/dx]+q(x) is Hermitian (self-adjoint) if we have that for any two functions u(x), v(x) in this vector space, [u*(x)p(x)dv/dx]ab=0, thus L has real...

I'm a student taking a non-calculus strength of materials course, and I believe I have what is probably a very simple misconception. I'm wondering why in the "eccentrically loaded column" b), which has two point loads placed at distances of equal magnitude from a centroidal axis, the moments...

Homework Statement Two pucks of equal masses collide in a non-head-on collision. Puck 1 with a velocitiy ##u_1 = 2.50\ m/s## impacts puck 2 at rest, in a 28-degree angle. Assuming no friction between the pucks, find their final velocities. Data: ##m_1 = 5.00\ kg## ##u_1 = 2.50\ m/s##...

Hi, In the often cited example of a person in a rocket traveling past Earth at high speed - I think I understand that both the person on Earth and on the rocket could view the other as being the party that's actually moving. And so if they could view the other party, they would both see the...

I've been watching the Khanacademy videos on Calculus and in this video, at 4:18: He talks about relative minima and maxima in an interval. He says that the relative extrema can't be at the endpoints. As far as I understand, in that case the interval would have to be an open one, but my...

I am studying parallel transport in order to understand Berry curvature, but I know this topic is most commonly used in GR so I'm posting my question here. I do not know differential geometry. I am looking for a general explanation of what it means to parallel transport a vector. Mostly I am...