Components Definition and 911 Threads

Homework Statement Prove that ## [L_a,L_b] = i \hbar \epsilon_{abc} L_c ## using Einstein summation convention. I think I have achieved the solution but I am not sure of my last steps, since this is one of my first excersises using this convention. Homework Equations [/B] ## (1)...

1. The Problem 2. The Free Body Diagram 3. The Question I've always had trouble determining the direction of the vertical and horizontal components in FBDs for statics problems, especially for a pin. Prior to looking at the solution, I wasn't sure on almost all of the directions of the...

Homework Statement A 12 m long uniform ladder, weighing 285 N, leans against the wall. The foot of the ladder is 6.5 m away from the wall. Determine the reaction components and the resultant reaction(magnitude & direction) if the coefficient of friction for static at the wall and the floor are...

This is a pretty hot and rarely understood topic in the automotive / racing industry. Sure, everyone knows spinning mass on a car is worse than mass sitting in a car. its effects are greater, but by how much? Besides the benefits of the unsprung weight having less gyroscopic forces...

The Dirac equation in 3+1 space-time yields spin, is this still true in 1+1d space-time? If not what do the 2 components of the spinor represent? Do we still have intrinsic spin in 1+1d space-time? Thanks for any help!

This question really does the need assistance of somebody trained in physical sciences. I've asked countless gun people and they are very opinionated but few of them can put forward answers that show they know anything about physical science. I myself dropped out of Engineering school halfway...

Homework Statement I am having difficulties in analyzing problems. Here are the problems: A1. A hiker begins trip by walking 25km southeast from her base camp. on the second day, she walks 40km in a direction of 60 degrees N of E, at which point she discovers a forest ranger's tower. Determine...

Homework Statement Find the equation of the horizontal components of two strings tied to a painting at 45 degree angles with the horizontal.Homework Equations Fnet = 0The Attempt at a Solution Since the painting is in equilibrium, I found that, in the horizontal direction, Fnet = 0 = S1x -...

This question just recently came up in a physics problem, but it's actually more of a math problem, so I'm going to ask it here. Let me provide some context. The HW was to show mathematically that the divergence of the curl was zero for the first part, and to explain it...

Im a little confused with this question, i can't quite seem to get the hang of it. I understand that you have to use a triangle and i understand that you need to use trigonometry, but what exactly am i even working out? What is the question asking? The image below shows the question, i am...

Hi, For a wave fixed at both ends, what is the behaviour of the original and refelcted wave between the harmonic frequencies? I understand how a standing wave is created by the superposition of a wave and it;s reflection at a boundary. I also understand that at the fundamental frequency of the...

1. A- What are the x and y components of a vector of magnitude 25m/s and direction of 45 degrees? B- What are the x and y components of a vector of magnitude 75N and a direction of 60 degrees.2. Are these the formulas you use? Vx=(R)Cos0 Vy=(R)Sin03. help please

I am trying to reconcile the definition of contravariant and covariant components of a vector between Special Relativity and General Relativity. In GR I understand the difference is defined by the way that the vector components transform under a change in coordinate systems. In SR it seems...

Consider the pith balls in the diagram: Both of them has mass 'm' and charge 'q'. The question asks for the charge on both the pith balls. The concept is a bit straightforward. But I am confused at the force distribution experienced by the pith balls. My text tackles the problem with...

Homework Statement You are given vectors A⃗ = 4.8 i^− 6.4 j^ and B⃗ = - 3.6 i^+ 6.8 j^. A third vector C⃗ lies in the xy-plane. Vector C⃗ is perpendicular to vector A⃗ and the scalar product of C⃗ with B⃗ is 19.0. Find the x -component of vector C⃗ . Find the y-component of vector C⃗ ...

Hey guys, So I have the stress energy tensor written as follows in my notes for the complex Klein-Gordon field: T^{\mu\nu}=(\partial^{\mu}\phi)^{\dagger}(\partial^{\nu}\phi)+(\partial^{\mu}\phi)(\partial^{\nu}\phi^{\dagger})-\mathcal{L}g^{\mu\nu} Then I have the next statement that T^{0i} is...

1. "William Tell is said to have shot an apple off his son's head with an arrow. If the arrow was shot with an initial speed of 55m/s and the boy was 15m away, at what launch angle did Bill aim the Arrow? (Assume that the arrow and the apple are initially at the same height above the...

Could someone credible please check my work on this one? Homework Statement This problem is "pulling a sled up a slope" All relevant data is in the picture. I wanted to find FP (The force one has to pull to start the sled moving up with slope). mass = 26.0kg μs = 0.096 slope of hill = 12...

Q.In the arrangement shown in fig. the ends P and Q of an inextensible string move downwards with uniform speed u. Pulleys A and B are fixed. The mass M moves upwards with a speed. ANSWER PROVIDED BY MY TEXT In the diagram ##vcos\theta=u## therefore ##v=u/cos\theta## HOW I TRIED TO DO THE...

Homework Statement I have a tricycle with a following data (see attachment): Distance (d) between center of front wheel (F) and center between rear wheels (C) = 325 mm Velocity of front wheel (VF) = 50 mm/s Angle of front wheel (α) = changing between -90;90 Distance between point C and P =...

Hi, I am working on a university project looking at material deposition systems. i came across a 30 second video on Youtube and i would be really interested to know how this product is achieving the speed and precision shown in the video. If anybody has any suggestions about the technology...

A roof purlin, supported by a roof rafter must support a 300 lb vertical snow load. Determine the component of of the snow load as a concentrated load “P” both perpendicular and parallel to the axis of the rafter. I read that the perpendicular component of the 300lb force can be figured out by...

Hi, we are currently working on Huygens constructions and I'm having trouble visualising it. I understand that, say if a light wave is incident upon an anisotropic material that if you consider it's electric field going perperdicular in one direction it will be refracted differently than if you...

For my homework I was given a velocity diagram of the Juan de Fuca plate similar to this: The first question is as follows: Measurements indicate that the Juan de Fuca plate is moving at a speed of ~40 mm/year. Calculate, and draw diagrams that show, the horizontal and vertical components...

Hello again, I've got another question that involves symmetrical components, this time I've attempted it. The Question follows: 1. In a 3 phase circuit with resistance earthed and neutral and Earth fault in phase “A” which produces a fault current of 800 amps. Load currents may be taken as...

Hello fellow engineers! I am a student doing a simple course in Electrical Engineering. I've got an enquiry regarding this question " 1. In a three phase 4 wire system with phase to neutral voltage of 230V, a balanced set of resistive loads of 8 ohms are connected between each phase and...

Homework Statement I need to work out the impedance of this notch filter, and what I really need is to know how to read the diagram, because if I can do that the rest isn't so hard. The diagram looks like this (I don't know if this uploaded right) So really, all I am trying to do is tell if...

Homework Statement You’re 5.00 m from the left-hand wall of the house shown in the drawing, and you want to throw a ball to a friend 5.00 m from the right-hand wall. You throw the ball so that at the peak of its trajectory it just clears the top of the roof...

Hello all, I am new here and very new to trig. I can't seem to figure out how this equation works out. I was wondering if someone could help me out with the long equation to get this answer. I know this is probably very simple to most of you but I am really stuck here... Thanks in...

I have problems with this question: This is how I resolved v into its components (Vr and Vtheta): So with this I get Vr = - V cos theta Vtheta = V sin theta However in my solution booklet the components are the other way around (Vr = - V sin theta, Vtheta = V cos theta) and I cannot...

Greetings women and men, I have a problem in which I have to find an angle \phi. http://srg.sdf.org/images/PF/StaticsHW.png A horizontal force of \vec{F}=400 lbs is placed on the structure at point A. Find angle \phi to give the AB component of \vec{F} a magnitude of 600 lbs. To solve this...

As you may know, the metric tensor for 3D spherical coordinates is as follows: g11= 1 g22= r2 g33= r2sin2(θ) Now, the Minkowski metric tensor for spherical coordinates is this: g00= -1 g11= 1 g22= r2 g33= r2sin2(θ) In both of these metric tensors, all other elements are 0. Now...

I have one question, which I don't know if I should post here again, but I found it in GR... When you have a metric tensor with components: g_{\mu \nu} = \eta _{\mu \nu} + h_{\mu \nu}, ~~ |h|<<1 (weak field approximation). Then the inverse is: g^{\mu \nu} = \eta^{\mu \nu} - h^{\mu \nu}...

Homework Statement Decompose H(x) into even and odd components Homework Equations e(x) = (f(x)+f(-x))/2 o(x) = (f(x)-f(-x))/2 The Attempt at a Solution i said f(x)=1 and f(-x)=0 and I got e(x)=1/2 and o(x)=1/2. but this isn't true. e(x)=1/2 but o(x) = 1/2 when x>0 and -1/2 when x<0. what...

Hi, I would like to know what the theoretical implication is, as it pertains to RC circuits of the following hypothetical situation(s): If one were to connected an ideal discharged capacitor in parallel with an ideal voltage source with zero resistance in the loop, the calculated RC time...

Homework Statement A man pushing a toy car causes it to undergo 2 displacements. The first has a magnitude of 150 cm and makes an angle of 120degrees with the positive x axis. The resultant displacement has a magnitude of 140 cm and is directed at an angle of 35 degrees at the positive x...

Hello, I am trying to understand Kaluza Klein theory on the five dimensional unification. It was mentioned over there: " Of the 15 components of gαβ, five had to get a new physical interpretation, i.e. gα5 and g55; the components gik, i,k = 1,...,4, were to describe the gravitational field...

Can someone please tell me the basics to how a cystal radio works? And also what are all the components that makes up a crystal radio? Thank you!

Homework Statement This problem has had me puzzled for hours. I really appreciate any help you can provide. A light plane leaves Shelburne, NS and flies 195km [N15°W] to Saint John, NB. After picking up a passenger, it flies to Moncton, NB which is 149km [N33°E]. The entire trip took...

"Is it possible for a vector that has nonzero magnitude to have a component in some direction that is equal to zero?" The answer key said that any vector that has a nonzero magnitude will always have a component of zero length in the direction perpendicular to the vector. I'm having trouble...

I'm a non-electrical engineering student however want to gain knowledge and experience with different electrical programming systems. I'm confused however as to all the different components and their differences. For example, why/when would you choose a PLC over an Arduino board or do these two...

I have pretty much learned how to derive the left side of Einstein's field equations now (the Einstein tensor that is). Now I need to grasp that stress energy momentum tensor. Does anybody know of any good sources that will tell me how to derive the components of this tensor? I ask this...

I have a homework problem where I have to solve for the displacements of the attached system using cyclic symmetry. To do this, I know that I have to find the harmonic load components of the system. One thing that my professor did not make clear (or if he did, I missed it) is how to determine...

I'm working on the electromagnetic stress-energy tensor and I've found this in a book by Landau-Lifshitz: T^{i}_{k} = -\frac{1}{4\pi} \frac{\partial A_{\ell}}{\partial x^{i}} F^{k\ell}+\frac{1}{16\pi}\delta^{k}_{i} F_{\ell m} F^{\ell m} Becomes: T^{ik} = -\frac{1}{4\pi}...

Hi all! I am currently learning fault study in power systems. To my understanding- In any network (symmetrical or unsymmetrical) , there would be 3 components- positive sequence component, negative sequence component and zero sequence component. Question: For generators and transformers ...

Homework Statement Two point charges, Q1 = -4.0 μC and Q2 = +3.0 μC, are placed as shown. In Figure 17.14b, the x-component of the electric field, at the origin O, is closest to: A) -3000 N/C B) 3800 N/C C) 9800 N/C D) -3800 N/C E) -9800 N/C Homework...

Hi everyone! First of all I would like to say that my native language is not english, so I will try to explain myself as good as I can This is my first thread in which I would like to ask a question a friend of mine asked to me, hoping he could get some answer from me, but I couldn't give him...

You go for a short walk traveling in three stages. The first displacement is 58.5 m 20.0 degrees east of north. The second displacement is 78.0 m 40.0 degrees south of east. Finally you go 99.0 m 17.0 degrees north of west. The answer I got was 36.9 m, 66.2 degrees north of west,which is...

Hi, I am having trouble understanding why Tij can be non-zero for i≠j. Tij is the flux of the i-th component of momentum across a surface of constant xj. Isn't the i-th component of momentum tangent to the surface of constant xj and therefore its flux across that surface zero? What am I...

I would appreciate if someone could set me straight here. I understand if I have an arbitrary operator, I can express it in matrix component notation as follows: Oi,j = <vi|O|vj> Is it possible to get a representation of the operator O back from this component form. I'm more interested...