Confused Definition and 1000 Threads

Homework Statement The sides of the biggest square have resistance ##R## and length ##L## (the amount of resistance in the wire is equal to the length), the smaller square is placed so that it's corners intersect midway through the sides of the larger square. Find the resistance between...

In "Einstein's Moon" by F. David Peat there is a description of the EPR thought experiment,but I am confused by Bohr's response to Einstein given in Peat's book. In the EPR as described by Peat, particle A and particle B move in opposite directions after the entangled particle (AB)...

1. From E=mc2 , m= E/c2 "c" being huge, "m" should be small. 2. m= mo/√ [1-v2/c2] if v= c, then m should reach infinity. 3. Photons moving with speed of light are massless particles. All the above statements are confusing me. (1) doesn't match with (2), (2) doesn't match with (3). Please...

I was confused about this example from a book. After putting in some numbers I got the forces circled in green and blue to be negative. Does this mean the directions for the forces shown is incorrect, and so I should switch the directions before calculating the reaction forces in the bearings (x...

Why is it that the smaller the black hole is, the more quickly it supposedly evaporates? It seems like a black hole should radiate energy proportional to the surface area of the event horizon. To me it seems like the evaporation should slow down the more the black hole shrinks because the energy...

Homework Statement A sphere of radius .06 m and mass .5 kg rolls down a ramp that is angled 30 degrees down the incline. It starts rolling from a height of 7 feet and does not slip What is its final linear velocity? Now, I used mgh=translational +rotational KE and found that the final velocity...

Homework Statement This Is more of a conceptual question. If the equation for dynamic pressure is 1/2(density)(velocity)^2 then as velocity increases the pressure would also, but I was told that as velocity increases pressure decreases. If anyone could explain this to me that would be great.

Hi guys! I'm a pharmacist who has been trying to understand how time dilation and Lorentz contraction and etc. work, out of pure curiosity. I have been reading a course by Michael Fowler, which I link the 4th section of: http://galileoandeinstein.physics.virginia.edu/lectures/sreltwins.html In...

I have a class like public class FriendList { public Dictionary<string, int> names { get; set; } // List of friends names and number of occurrences (in case two or more friends have the same name) public DateTime timestamp { get; set; } // date/time on the data file...

Extremely confused on finding eigenvectors? Below I have a picture that gives the matrice and the eigenvectors. How did the solution find these eigenvectors?? i.e. the eigenvalues are 7 and -2 IMAGE LINKS http://tinypic.com/r/2liii68/9 http://tinypic.com/view.php?pic=2liii68&s=9#.VkY_YfmrSUk

I'm a computer scientist who was recently given a book about quantum physics. I am confused about something in the book. Imagine shining an x-ray (produced by copper K alpha 1 emission) on an aluminium foil. I understand the basics of photoelectric effect. You shine the x-ray on target aluminium...

Hi, This is also a sort of geometry question. My textbook gives a proof of the relation: sin(θ + Φ) = cosθsinΦ + sinθcosΦ. It uses a diagram to do so: http://imgur.com/gLnE2Fn sin (θ + Φ) = PQ/(OP) = (PT + RS)/(OP) = PT/(OP) + RS/(OP) = PT/(PR) * PR/(OP) + RS/(OR) * OR/(OP) = cosθsinΦ +...

Hello PhysicsForums Readers, I need some advice concerning studying habits and techniques. I just started engineering undergrad in Canada, and while I feel I'm adequately intelligent to succeed here, my studying habits might possibly kill me. I feel like I love math and physics and the topics...

So I was reading a solution of a problem that has to do with integration in polar coordinates, and in one of the steps it did this How did these terms (circled in blue) change like that? I've never seen a step like that before..

Homework Statement I have the time and distance measurements. We shot it straight up, how can I find the altitude and angles? Times: (6.58 sec, 23 m), (6.90 sec, .6 m) (6.20 sec, 10 m). The time represents how long it takes for the rocket to shoot up and fall, the distance is the measurement...

Hey all, I am reading Goldstein and I am at a point where I can't follow along. He has started with D'Alembert's Principle and he is showing that Lagrange's equation can be derived from it. He states the chain rule for partial differentiation: \frac{d\textbf{r}_i}{dt}=\sum_k \frac{\partial...

I'm confused about the resistances of common electrical appliances. v=ir So I was reading something about how fast iphones charge with different chargers and it got me thinking about the resistance of things like phone batteries. So it said that it could charge at 5V and 2 amps, but also at 5V...

Good evening people. Recently I started taking the "electric network analysis" course in my school. We already saw the mesh analysis method for solving circuits. Now we are seeing the node analysis method. I understand that the first step for this method is finding the number of nodes (and one...

Hello everyone, Since yesterday I'm struggling with concept of CoG and of course in CoM. The problem is that I don't understand why lower to the ground CoG is more stable then CoG more off the ground. On the internet there is batch of information about that but nobody explained it by momentum...

So, I've learned in school that the energy of a wave is proportional to the square of its amplitude. I've also learned that the energy of light is given by E= hv. I'm confused. Could someone clarify?

Hi guys :) I am in the uk and will be going to university to study physics and the aim is to go on to do a phd in fundamental theoretical physics either in the uk or in the usa However I am getting confused on what is better to study at undergrad between maths and physics as a lot of the phds...

Homework Statement So I saw a unit "W/(g2 cm3)" And I'm pretty sure it's about power density...and I understand what W/cm3 is. It's watts per cubic centimeter...but what does the g mean? grams? If so, how does that fit in? :/[/B]

I'm having a very hard time understanding the concept of a "Normal Force." The only framework with which I've come to terms with is imagining the Normal Force as the force exerted when object A comes into contact with object B which keeps object B from losing its macroscopic structural...

Homework Statement Calculate the total power generated by G Homework Equations P=VI The Attempt at a Solution I used the P=VI formula to calculate the total power generated by G which is 40W, and the answer turns out to be correct. But actually, I don't quite understand this topic of opposing...

I don't understand what is meant by "derive the formula for finding the volume of a sphere that uses infinitesimals but not the standard formula for the integral"? Is this talking about Gauss or what? I'm completely self taught in calculus and I did three proofs already... the old cylinder /...

Homework Statement a. k(t) = (sqrt(t+1))/(2t+1)b. y = (3^(x^2+1))(ln(2))The Attempt at a Solution For the first problem, I know I use the quotient rule for derivatives (L)(DH)-(H)(DL)/((L)^2) which would go to: ((2t+1)(1/(2sqrt(t+1)) - (sqrt(t+1))(2))/((2t+1)^2) I get stuck here, maybe it's...

The decay \rho^0 \rightarrow \pi^- \pi^+ occurs with a probability of 100\%, whereas the decay \rho^0 \rightarrow \pi^0 \pi^0 does not occur in nature, due to isosphin conservation. I don't understand this. Looking at the Isospin and its third component ¦I,I_3\rangle we have in the first...

I have some confusion over some diagrams involved in proton decays in SU(5). I've seen a few like this that look weird to me. Here is one I found where the colored Higgs triplet does the job: Straight away I don't know what to make of this because I've only ever seen diagrams where fermions are...

A comparison of corresponding parts of these two similar isosceles triangles yields velocity triangle displacement triangle where |-vo| = |vf| = v In a small time interval Δt, the arc length s → c. Okay, so I got this from Physics LAB, and I don't understand the last statement that...

A manufacturer quotes a standard CO2 canister contains 16g of CO2 at a volume of 20cm^3. So I need to calculate the pressure in the canister... Using ideal gas law P = nRT/V n = 0.364mol (16 of co2) R = 8.314 J/Kmol (universal gas constant) T = 294k (gas is at room temp 21 deg C) V = 20cm3...

Homework Statement Homework Equations dsinθ =nλ The Attempt at a Solution I don't understand why an interference pattern will only be observed along XY only. Why don't the waves intersect along RS. Does it have something to do with R being the midpoint of PQ?

Homework Statement 2. Homework Equations [/B] KE=1/2 mv2 The Attempt at a Solution To calculate the kinetic energy of the ball just after it leaves the surface, I use the ratio of the centre of gravities of the ball at the two different heights. My working is (0.41/0.76)×0.75 which gives me...

Homework Statement Hi, I am just trying to wrap my head around using path integrals and there are a few things that are confusing me. Specifically, I have seen examples in which you can use it to calculate the ground state shift in energy levels of a harmonic oscillator but I don't see how you...

Part (a) is easy to do by setting up a triple integral, but for part (b), I was a bit confused by the diagram provided by the solutions manual: Why is the spherical wedge (shaded) graphed on the z-y axis? In the most general case, shouldn't the two lines that form angle $\phi_1$ and $\phi_2$...

For details and to try to explain the above, the complex scalar field is a useful example. The complex scalar field has an action S=∫d4x(∂μϕ∗)(∂μϕ)−V(|ϕ|). There is a global, continuous symmetry to this action -- an overall phase. That is, if one replaces ϕ→eiαϕ, then the action does not change...

Hi all, This isn't actually part of my assigned homework, I was just trying it out as the topic confuses me. I think I might understand what's going on a little more if someone could walk me through this. Any advice on the intuition behind it would be great. Thanks so much. 1. Homework...

some time ago I posted a question re acceleration data. I bought an accelerometer and logged some data. when stationary the accelerometer (can mention the brand if that is not spamming) read 1g, when thrown in the air got what was expected with 0g ie weightless when the accelerometer switched...

Hi. For the angular momentum l=2 case are the L2 and Lz matrices both 5 x 5 matrices with the following eigenvectors ? ## \begin{pmatrix} 1\\0\\0\\0\\0 \end{pmatrix} ## , ## \begin{pmatrix} 0\\1\\0\\0\\0 \end{pmatrix} ## , ## \begin{pmatrix} 0\\0\\1\\0\\0 \end{pmatrix}##,## \begin{pmatrix}...

I understand how to do calculations involving potential difference but I've never been able to find any information that helps me understand what is physically happening to cause it. My assumption is that for a PD to occur, there must be a build up of charge to cause the difference in...

Homework Statement So, I'm doing a series problem, and after applying the root test I end up with the following limit: Lim as n--> inf of (n! / n^2) = infinity according to the solution manual. I can't seem to understand this because the way I look at it, each term in the numerator is...

The principle states that two electrons cannot have the same quantum numbers. And I've read that this applies to "fermions"- protons, neutrons, 1/2 spin particles. But how exactly does this apply to, say, a proton? Sorry if I sound stupid...I've got all my knowledge about this through the...

First off I would like to thank you for your time for clicking on this thread and reading it. Thank you! To begin, I'm a 17 year old in High School in 11th grade in Northern New Jersey. To give a little background in my schooling life, just like pretty much everyone else I did great in all...

Even though the big bang wasn't an actual explosion per se it did have the expansive characteristic of an explosion right? At some point in time during the expansion two bodies might be x distance apart. A little farther down the timeline those same two objects would be farther from each other...

i know that short circuit is when current is max while resistance is zero and open circuit is when resistance is infinite and current is zero, but in terms of voltage, if i have a part of circuit and i want to know whether it is short or open circuit and i only know : the voltage and if the...

Generate 225 samples of size 625 random numbers from U(10,22). For each of these 225 samples calculate the mean. a) Find the simulated probability that the mean is between 10 and 11. b) Find the mean of the means. c) Find the standard deviation of the means. d) Draw the histogram of the...

Homework Statement Actually its not a homework problem sort of thing...I was wandering through a book , studying waves then I realized that there were two formula for the same thing ...the velocity of a wave. Homework Equations v=λ/T [where λ is the wavelength and T is the time period]...

Hello, I am self-studying an introductory mechanics textbook and while I feel I understand the material there pretty well, I came across across an online definition of position which seems at odds with the explanations and definitions in my book. The definition that confused me is: ""Position...

I'm looking at Tod and Hughston Introduction to GR and writing the metric in the two forms; [1]##ds^{2}=dt^{2}-R^{2}(t)(\frac{dr^{2}}{1-kr^{2}}+r^{2}(d\theta^{2}+sin^{2}\theta d\phi^{2}))## [2] ##ds^{2}=dt^{2}-R^{2}(t)g_{ij}dx^{i}dx^{j}## where...

If a wavefunction can be in different states each with a different eigenvalue when operated on by an Hermitian operator then am I correct in thinking that the expectation value of that operator when acting on a superposition of states could give a value that does not equal any single one of the...

Hi! I have a few questions about resonance: 1) What exactly is the "amplitude of driver of oscillation"? And why is the amplitude of the driven object equal to the amplitude of the driver right from the start when the driver frequency is 0? 2) Is the driven system originally oscillating? 3)...