Difficulty Definition and 261 Threads

Hamiltonian is in the form ##H = H_0 + \lambda W##, where ##\lambda \ll 1## and ##W## is the perturbation. Assume the eigenstates ##\mid \psi(\lambda) \rangle## and engenenergies ##E(\lambda)## can be expanded in a power series of ##\lambda##. $$\mid \phi(\lambda) \rangle = \mid 0 \rangle +...

Hi all, first post, I hope this is the right place. As I understand, voltage is a measure of the energy given to each coloumb of charge. Therefore, a cell with a higher emf will give more joules of energy to each coloumb of charge. However, voltage is also the driving force behind getting...

Hi all, I'm having problems with visualising shearforce for a body.Let us take a rectangular prism and fix one of its ends.Let the other end be subjected to a tensile force T Newtons.The normal stress acting on the cross section is the tensile force /area of cross section perpendicular to...

\exists{x}(P(x)\Rightarrow{Q(x)})\equiv{\forall{x}P(x)\Rightarrow{\exists{x}Q(x)}} I am able to derive this equivalence by using the standard equivalences of symbolic logic, but when I try to verify this semantically, with an example, I just can't see why these two expressions are equivalent...

Hi all, I have a conceptual difficulty with the idea of induction of a current in a wire due to a changing magnetic field. Initially I was very comfortable with the idea. Upon seeing the typical setup of a square wire being rotated in a region of uniform magnetic field, I was happy to accept...

Homework Statement I attached the original problem and a diagram I made with the variables on it. Basically we have a rod hanging from a wire at an angle theta with tension and the other end floating in water. So there is T=tension, weight=w=mg and buoyant force=F_b. I introduced symbols for...

I've heard that engineering (generally) is less difficult than physics but I've also heard that ChemE is the most difficult engineering degree to get. So which is more difficult to get: a B.S. in Physics of a B.S. in ChemE? If ChemE is eaiser, exactly how much easier is it: considerably or only...

i attempted the first 100 pages of Walter Poor's Differential Geometric Structures, taking me about two months, and the most difficulty i had was trying to understand the utility(?) of the pullback bundle. its possible that its just a very difficult subject and the only thing that's needed is...

Right I am having an issue with the proof to permutation, I really can see the n-r-1 I think the confusion stems because it is in the general term, which throws me a bit, if possible could someone maybe write it in numbers and the underneath write in the general term if not too much trouble. The...

I apologize if this seems much too "freshman", and may come across as annoyingly simple to some more trained or educated on this board. However I will ask the question anyways as I have failed to find an answer elsewhere. Under Newton's Second Law of Motion, f=ma. thus F = kg (m/s^2)...

Hi, I am trying to analyze the effects of pressure on the automotive t=ire by modeling and simulating the same in ANSYS workbench. However, I am having trouble applying material conditions to the model. I wish to use mooney rivlin material but when I apply that based on the guidance given by...

Homework Statement Hi guys, I'm having real difficulty with understanding accumulation points. I don' really know why that is since others seem to understand the concept fine but I'm very lost. For example, I'm practicing some questions and one of the is : If S is the set of rational...

I'm trying to keep a balance in difficulty next quarter and would appreciate some feedback as to the difficulty of these classes. The four I'm choosing between are Linear Algebra (upper division), Linear and Nonlinear Systems of Differential Equations, Ordinary Differential Equations, and...

Hello all, I am preparing to transfer to a University of California campus as a junior from a community college. I am applying to several campuses next month and I'd like some guidance in choosing a school for when the time comes to select one. One of the major things I am thinking about...

I'm trying to find the derivative of: $$f(x)=(3x+1)^2(2x-3)^3 \text{ by using the product method}$$ Here is my working out so far, using product rule:$u'v+uv'$ $$\frac{d}{dx} (3x+1)^2(2x-3)^3= 2(3x+1)\cdot 3 *(2x-3)^3+(3x+1)^2\cdot3(2x-3)^2\cdot2$$ Simplified...

First post, but I've lurked this site for a few years. I was wondering if anyone has found themselves in a similar situation or had any advice. I currently have a B.S. in Nuclear engineering, graduated about 10 months ago, and have had zero success in finding related work. During school I...

Hi everyone. I am currently attending the University of Washington, and after talking to a few advisers it has become apparent to me that Physics 121 (first course in the calculus based physics series) is not recommended to people that haven't taken the entire calculus series yet. They explained...

hi all, im new at electromagnetics and vector calculus, so facing these trivial problems. The differential form of gauss's law for empty space states ∇E = ρ/ε .The right side refers to charge density at the point of calculation of divergence? If a point charge(or a small uniformly charged...

my basics and concepts in physics are relatively the best among my classmates but i have not done expected amount of problems that require IPhO. i am from India and first level NSEP is on 25 november 2012 so i have about 100 days for problem practice. I have collected the following books -...

If the force applied on ab object due to gravity is -mg why is applying a force of mg give upward raise the object if the two forces are equal and opposite in direction. I would think the object would remain still until you apply a force greater than mg.

In our world where 'c' is large, most people intuitively understand Galilean addition of velocities at everyday speeds i.e. if someone stands 40m behind me and rolls a ball towards me at 10m/s (assuming we are not moving relative to each other) it takes 4s to reach me. If we repeat the...

Hello! I'm doing some calculus exercises and I'm having some difficulty to find the right answer. Homework Statement The integral is \int \frac{1}{\sqrt{5x+8}}dx and the exercise tell me to solve this by using (a) u=5x+8 and (b) u=\sqrt{5x+8} Homework Equations The Attempt at a Solution This...

How difficult is abstract algebra or group theory, plus complex analysis in relation to calculus?

As the title implies, I am a current engineering major currently having difficulty in the physics material that I need to study for my major. I am in a position where I am considering a possible major change because I am currently questioning if I will be able to make it through the physics that...

Homework Statement Hi! I'm not being able to solve this integral: \int \sqrt{2ax}\; dx We have started with integral yesterday and I don't know much yet. Homework Equations The Attempt at a Solution This is what I tried to solve the integral \int \sqrt{2ax}\; dx = \int...

I was planning on just taking physics courses next quarter (3, maybe 4 total) but I have an interest in taking a number theory course. Would it be too much to pile on with QM, Relativity, a physics-based math course, and part II of E&M? I know this question is impossible to answer because each...

For any system where the thermodynamic limit exists, we know that the internal energy U, the entropy σ, the total particle number N and the total volume V are all extensive. Because of this, we know that the Euler relation holds true U = -PV + \tauσ + \muN and that the chemical potential...

Homework Statement Hello! I'm having some trouble to find this limit \lim_{x\rightarrow \pi}\frac{senx}{x-\pi } Also, limits like this one \lim_{x\rightarrow \frac{\pi}2{}}\frac{1-senx}{2x-\pi } confuse me a lot!Homework Equations The Attempt at a Solution I don't even know where to start! I...

Homework Statement Hello! I'm having difficulty to find this limit: \lim_{x\rightarrow -1}(\sqrt[3]{\frac{x^3+1}{x+1}})Homework Equations The Attempt at a Solution This is what I'm trying to do to solve this limit: Let \frac{x^3+1}{x+1}=u then \lim_{x\rightarrow -1}(\sqrt[3]{u}) =...

Hello! I'm having difficulty to find this limit: \lim_{x\rightarrow -1}(\sqrt[3]{\frac{x^3+1}{x+1}}) This is what I'm trying to do to solve this limit: Let \frac{x^3+1}{x+1}=u then \lim_{x\rightarrow -1}(\sqrt[3]{u}) = \lim_{x\rightarrow -1}(\sqrt[3]{-1}) I know something is wrong I'm just not...

I am learning about tensors. Can somebody give me some help. Thanks.

I've come across the following question: ∫∫∫6xy dxdydz where R lies under the planez=x+y+1 and above the region in the xy-plane bounded by y=0,y=√x and x=1. Now the limits would be: √x→y→0 ; x+(√x)+1→z→2 and ?→x→1 Now I can't get the upper limit of x as a...

I am trying to understand how the Schwartzschild metric works and coming to the conclusion that if I drop an object that it will not fall to the Earth but just stay there when I open my hand. Therefore, I'm confident I have made a mistake, but I don't see where it is. Here is the metric...

I'm having some difficulty in working with units of mass at the quantum level. This difficulty most clearly manifests itself when I'm doing a Compton scattering problem. Recall that Compton scattering is given by \Delta \lambda =\frac{h}{m_{e}c}(1-cos(\theta )) and that the rest mass of an...

Homework Statement 1. Determine the largest open interval where the function f(x)=2x-5/x+3 is increasing AND concave up (at the same time) Homework Equations The Attempt at a Solution I've run through the problem and arrived at a second derivative of f''(x)= -22/(x+3)^3...

I was browsing through a few schools websites, and apparently, UCR, UCLA and UCSD do not force Chemistry PHD candidates to take a written comprehensive exam! However, the Physics PHD candidates take a brutal and long comprehensive exam consisting of 2-3 quarters each of advanced quantum...

Hi I'm having trouble to fully understand the concept of Genus: https://en.wikipedia.org/wiki/Genus_(mathematics) Those examples are preety simple to me Genus = number of handles/holes. But what the wikipedia doesn't cover (at least visually) is when these handles or holes share space like...

Just about all of the problems in my calculus textbook range on average range between 4 and 8 steps. Once you know the algorithm the problems are usually easy and routine. It is simply a matter of understanding what the algorithm requires. Ironically the hardest part about math is...

I'm taking a combinatorics course this semester (from the math department), and my professor said the exams are usually devised so that the average score is a 60%, and then they're curved. I've seen this method of exam development with other professors, so I wanted to get some input to help...

Plz help me out with this difficulty. Here is a figure showing two conducting spheres(haven't drawn all EF lines):- Here is the problem, Suppose one of the spheres is charged with a charge +Q, other is neutral , so charges will get induced as shown in figure. The left portion of orange...

Hey PF. I've got a month of break before classes start again, so naturally I'm going to spend it nose-down in books like a good little nerd. Trouble is, I don't want to use a shotgun approach to self-study; I'd rather use a focused approach on what I think might present the greatest difficulty...

In his "an introduction to quantum field theory", problem 5.4 (c), he describes a bound state of positronium as |B(k)\rangle=\sqrt{2M}\int{\frac{d^{3}p}{(2\pi)^{3}}\psi_{i}(p)a^{\dagger}_{p+\frac{k}{2}}\Sigma^{i}b^{\dagger}_{-p+\frac{k}{2}}|0\rangle} where \psi_{i}(p) are the p-orbtal...

Note: as i was typing this post, i think i figured out the answer but i want to confirm. Question: let A denote the set of points that are interior to, or on the boundary of, a square with opposite verties at the points (0,0) and (1,1). let Q(A) = ∫∫dydx if C, a subset of A, is the set...

Hi In my notes I came across the following sentences:- Any signal consisting of the system's characteristic mode is sustained by the system on its own. The system offers no obstacle to this signal. Not getting what it means. Please, a little help needed. :-) Thanks salil

Within the next year, I'm transferring from the local community college to the state university to complete my BS in chemical engineering. Right now I have about 3.5 gpa in my lower division courses (math, chem, physics, intro engineering, etc). Obviously, I'm going to work as hard as I can to...

From Richard Feynman's Nobel Prize Speech. It must be clearly understood that in all this work, I was representing the conventional electrodynamics with retarded interaction, and not my half-advanced and half-retarded theory corresponding to (1). I merely use (1) to guess at forms. And, one...

Hi, I suffer from immense algebraic difficulty. I always understand the material in math 90-100%, but I always flunk on tests (last I got 12%...) because I'm so clumsy with numbers. Are there any practices that focus specifically on that?

Homework Statement The Attempt at a Solution The above is my work. The problem is trying to make sure the inverse is element of the subgroup. Any leads? Also, was I correct in solving for x and y in that fashion?

Homework Statement [PLAIN]http://img851.imageshack.us/img851/5741/86853377.jpg The Attempt at a Solution For the long straight wire, the charge per unit length λ is already given, this is distributed on the surface of the wire. The electric field is zero for anything less than r1...

So I need to decide by tomorrow, whether I'll be taking topology or diff geo, (along with real analysis and advanced linear algebra). I've sat in on both classes for the first lecture, and I'm still not certain which class would be more difficult. My diff geo class has no exams, and instead...