Normal Definition and 1000 Threads

I am not sure if i get this part of a book i am using: Why are the mwo²xa acting too? Is not 2kxa enough?

Hey there, I've been recently been going back over the basics of GR, differential geometry in particular. I was watching one of Susskind's lectures and did not understand the argument made here (26:33 - 35:40). In short, the argument goes as follows (I think): we have some generic metric ##{ g...

I have trouble understanding the solution to a homework problem. Consider the interaction Lagragian ##\mathcal{L}_{\rm int} = -iqA_\mu \bar{\psi}\gamma^\mu \psi##, i.e. photon-electron/positron interaction. We want to focus on the Compton scattering $$e^-(\vec p_1, \alpha) + \gamma(\vec p_2...

Dear Every one, I have a question about when is to a good idea to mod out a normal subgroup of group. Any examples would help me out. Thanks Cbarker1

This is a question from an exercise I don't have the answers to. I have been trying to figure this out for a long time and don't know what to do after writing mx''¨(t)=−kx(t)+mg I figure that the frequency ω=√(k/m) since the mg term is constant and the kx term is the only term that changes. I...

I am learning about hypersonic flow now and there seems to be a lot of discussion about the effects on oblique shock as the Mach tends to be very large. I was wondering what happens to the normal shock as the Mach number tends to be high and I can't seem to find anything about it. Is it because...

Hello everybody, I have to find the amplitudes of a wave that goes through 4 different mediums in terms of ##E_0##, suffering reflection in the first three but not the last one. I calculated the corresponding reflection indexes of the three mediums (all of them real). Following calculations, I...

Block A is accelerating at a= 49.6/0.5 m/s (99.2m/s) Block B force is F= 3kg * 99.2 = 297.6N but I'm not sure where to go from here?

My understanding is that you can describe the complicated motion of atoms in a crystal as a sum of standing waves (normal modes). A phonon is an excitation of a normal mode in the sense that it increases the vibration amplitude of that normal mode and the energy of that mode by a quantized...

Hello everyone, someone could explain me please, why the work of the normals forces are 0 ? He used with conservation energy equations. How should I refer to the displacement point ? Thx everyone !

Hi! I have question about high frequency transformers inside switch mode power supplies (SMPS). Is it normal for them to become hot under no load or low load? For example if power supply is rated for 144A at 13.8V and I only pull from it 2A at 9.6V, it normal that transformer becomes about 50C...

Clearly e ∈ N. If a, b ∈ N, say ##a^k = b^l = e##, for some k,l ∈ N, then ##(ab)^{kl} = (a^k )^l (b^l )^k = e^l e^k = e##; thus, ab ∈ N. Also, ##|a|=|a^{−1}|##, so ##a^{−1}## ∈ N. Thus, N is a subgroup. As G is abelian, it is normal. Take any c ∈ G. If, for some n ∈ N, we have ##(cN)^n = eN##...

I found the equations of motion as ##m\frac{\mathrm{d}^2x_1 }{\mathrm{d} t^2} = -\frac{mg}{l}x_1 + k(x_2-x_1)## and ##m\frac{\mathrm{d}^2x_2 }{\mathrm{d} t^2} = -\frac{mg}{l}x_2 + k(x_1-x_2)## I think the k matrix might be ##\begin{bmatrix} mg/l + k & -k \\ -k & mg/l + k \end{bmatrix}##...

Hi everyone I can't understand how normal force produce torque isn't normal force acts normally on the plane so the perpendicular distance in case if it was like block will be zero, so normal force doesn't produce torque. "case of box"

Problem: Let $X_n$ be independent random variables such that $X_1 = 1$, and for $n \geq 2$, $P(X_n=n)=n^{-2}$ and $P(X_n=1)=P(X_n=0)=\frac{1}{2}(1-n^{-2})$. Show $(1/\sqrt{n})(\sum_{m=1}^{n}X_n-n/2)$ converges weakly to a normal distribution as $n \rightarrow \infty$.Thoughts: My professor...

Let's try inputting a solution of the following form into the two-dimensional wave equation: $$ \psi(x, y, t) = X(x)Y(y)T(t) $$ Solving using the method of separation of variables yields $$ \frac {v^2} {X(x)} \frac {\partial^2 X(x)} {\partial x^2} + \frac {v^2} {Y(y)} \frac {\partial^2 Y(y)}...

Σ F= -F(gravity from earth) + F(normal from earth) -F(normal from top box) +F(normal from bottom box) = (2+5) * 2.5 The forces from gravity and it's normal force cancel out, leaving us with the normal forces from the boxes. F(net of normal from boxes) = (2+5) * 2.5 = 17.5N

Hello all! I have a mathematical question for you. I'm trying to design a thrust bearing that can withstand axial and moment loads. I've added a picture of a similar design. The design consists of two rings (grey) and sliding pads (blue) fixed on the bottom ring. The top ring slides over the...

a) P(X<18) = (18-20)/sqrt25 =-2/5 =-0.4 then you use the standard normal table and find that; P(X<18)=0.3446 b) P(X>27) = (27-20)/5 = 7/5 = 1.4 P(Z>1.4) =P(Z<-1.4) =0.0808 C) =(13<X<23) =13-20/5 , 23-20/5 =-7/5 , 3/5 =-1.4 , 0.6 P(Z<0.6)-P(Z<-1.4) =0.7257-0.0808 =0.6449

How to find K value from the following equation (1) a*n(d)-b*N(d)=0 (1) where d= ln(c/K)+b (2) where n(d) and N(d) are normal density function and cumulative normal function.

Guys I was just wondering if normal force is a contact force. Obviously it is considered a contact force but it also has something to do with the repelling of atoms. In my mind, normal force is a fundamental truth, but technically, are two objects touching or is there a minuscule space between...

Hi! i have this exercise and solution : Exercise: steel plate given in figure (a) is joined by an inclined butt weld ,the plate is subjected to tensile stresses in both x and y directions, σ(x)=54 N/mm^2 and σ(y)=38 N/mm^2 , 1) Determine the normal and shear stresses of the butt weld...

I want you to tell me if I'm right For 1), does ##m_2## feel a normal force? Because I don't think so, since it isn't pushing the wall. For 2), ##m_2## suffers a normal force because it feels a pseudo-force to the left and so it pushes the wall

A welded square frame consisting of four equal rods each with mass m and length 2l can move in the vertical plane by means of two small wheels in A and B that move without friction along a horizontal and vertical track, respectively. The disc is released from rest in a position where the sides...

Does the time ordering operator ##\mathcal{T}## commute with the normal ordering operator ##\hat{N}##? i.e. is $$[ \mathcal{T},\hat{N}] =0$$ correct?

I have a series of pulleys where the belt is running around them in a way to describe a sine curve. The pulleys are stationary and the belt is running from left to right. For every particle of the belt I can use standard formula to calculate their normal acceleration, when in contact with the...

What's really the difference between pressure and normal stress? Also I know pressure acts normal to a surface from the outside Do normal stress acts from inside? I'm reading bird transport phenomena and this is confusing

I am not able to understand why normal force on top in a vertical circular motion the least. Also please help me with normal force of a body over convex and concave bridges. Why do we get these equations: N=mg-mv2/r (convex bridge) N=mg+mv2/r (concave bridge)

Hi, I was watching this Youtube video (please remove the parentheses) : https://youtu.(be/mtH1fmUVkfE?t=215) While watching it, a question came to my mind. In the picture, you can easily calculate the total number of customers. It's 1000. For my question, I'm going to use the same picture...

For equilibrium, using ##\Sigma \vec F = 0##, we get ##n_1 + n_2 = 300\; \text{N}##. Taking the system as a whole and applying ##\Sigma \vec \tau = 0## about the hinge (pin) at the top from where the load is hung, we get ##n_1 \times (0.8) \times 4 = n_2 \times (0.6) \times 3##, by taking...

How does " an axis normal to the plane containing the structure" look like?

Hi, The following is called normal form of the conic section equation: x²+y²+2ax+2by+c=0 A circle is one of the conic sections when considered as a special of ellipse. I'm confused as to why the the given equation is called "normal form of the conic section equation" when, in my opinion, the...

My approach: Let us take two orthogonal axes: x, parallel to the racket's plane and y, perpendicular to it. For the ball to not spin, the components of initial velocities of the racket and the ball along x-axis must be same. Also, as the line of collision is along the normal to the racket's...

I’m worried I’m going to get my PhD knowing GR but having a less-than-undergrad grasp on the other core topics like stat mech and QM. I feel like “forgetting” most of core physics makes me a bad physicist. Or is this normal when you specialize? How do y’all stay sharp on these topics?

I have came across a problem where each point of a surface parallel to the x-y cartesian plane and having it's normal along the z axis is having velocity along the z direction ##v_z## and there exists a velocity gradient across the plane (e.g ##v_z(x,y)## , After time ##\delta t## it is written...

Hello. I would like to draw (sample) several random vectors x from a n-dimensional multivariate normal distribution. For this purpose I want to use C++ and the GNU Scientific Library function gsl_ran_multivariate_gaussian ...

https://postimg.cc/JtP2h113 I think I may have forgotten some more basic elements of tension and normal reactions. I do not understand why the vertical component of the normal reaction =Tsin60-15g Because Tsin60-15g is negative when resolving upwards, i would have thought this meant that the...

First I worked out the dispersion relations, which is pretty easy: ##M \ddot x_j = K x_{j-1} + K x_{j+1} - 2K x_j -mg \frac {x_j} {l} ## (All t-derivatives) We know ##x_j## will be in the form ##Ae^{ijka}e^{-i\omega t}## so the above becomes: ## -\omega^2M = K (e^{-ika}+e^{ika}-2)-\frac {g}...

Summary: Calculations of glass thickness for aquarium 140cm (length), 55cm (width) and 80cm (height). Scenarios for normal glass and tempered glass. Hi everyone ! I want to ask you for help to calculate how thick (minimum version and save version) should be a glass for aquarium with sizes...

Consider a body inside an elevator. When it goes up and down, I believe that normal work (positive on the rise and negative on the descent). My question is: since the total work on the closed path is zero, can we say that the normal force is conservative?

Dear Everyone, I am struck on a problem dealing with normal subgroups. The problem is the following: Let $G$ be a group, $H$ and $K$ be normal subgroups of $G$ with $H\ge K$. Prove that $H$ is a normal subgroup of $K$ Prove that $K/H$ is a normal subgroup of $G/H$. My attempted work...

one book example $\textsf{Suppose that A is a matrix whose characteristic polynomial is}$ $(\lambda-2)^2(\lambda + 1)^2, \quad \dim\left(E_2\right)=1 \quad \dim\left(E_{-1}\right)=2$ $\textsf{Find the Jordan Normal Form of A Find the Jordan Normal Form of A}$ $$\quad \dim\left(E_2\right)=1...

nmh{1000} Suppose that A is a matrix whose characteristic polynomial is $$(\lambda-2)^2(\lambda+1)^2$$ find all possible Jordan Normal Forms of A (up to permutation of the Jordan blocks).ok i have been looking at examples so pretty fuzzy on this for the roots are 2 and -1so my first stab at...

I've been reading this book, in which the author expresses the vacuum projection operator ##\vert 0\rangle\langle 0\vert## in terms of the number operator ##\hat{N}=\hat{a}^{\dagger}\hat{a}##, where ##\hat{a}^{\dagger}## and ##\hat{a}## are the usual creation and annihilation operators...

Homework Statement Here's a snapshot of the problem: Homework Equations + Newton's 2nd Law. The Attempt at a Solution My question is: why does the delta P term have only a single 40 kN force considered, whereas for delta EF there's an F/2? Thanks for your time.

A 10 kg block sits on a board inclined to an angle of $30^\circ$ with the horizontal. What are $F_{inc}$ (force along the incline) and the $F_n$ (force normal)?How to compute this?

In some classes that I have taken in university, it's become sort of a common practice for instructors to allow students to create cheat-sheets that they can refer to while taking tests. They claim that the process of creating this cheat-sheet will allow students to help remember what they must...

Hello all: Can you use current of shelf multicore PC as a high performance computer Can it handle the job ? Dose the outcome data tables and simulation results , is correct and with low error margins With out gpu like cuda or opencl Best Hagop

Hello. This is a basic statics/mechanics of materials problem. Here's an image of my work. I've taken a course in statics before, and this is supposed to be review, but I can't seem to get the correct answers which are V_c = 75 lb, M_c = 1125 lb*ft. I've chosen the right side, and it seems as...

I am trying to determine a normal stress balance at an axisymmetric and dynamic fluid-fluid interface, ##z(r,t)##. For a static, free surface, this simplifies to the Young-Laplace equation: $$ \Delta p=\rho gz-\sigma2H=\rho gz-\frac{\sigma}{r}\frac{\partial}{\partial r}\left(r\frac{\partial...