Sign Definition and 596 Threads

There are a few details, either convention or understanding, that I was hoping someone could help to clarify. Consider the object below, acted upon by a few forces including an unknown ##\vec{N}##, which I have split into its horizontal and vertical components ##\vec{N_{x}}## and...

Hello, As far as I know, the standard sign convention for Kirchhoff's law are: For resistor: the potential difference (voltage) is negative if the chosen loop direction is the same as chosen current direction through the resistor, positive otherwise. For battery: the voltage is positive if the...

I find most of the errors I make are related to arithmetic or using the wrong sign. (Note: This applies to mainly algebra and trigonometry for me.) I've tried writing slower and neater, and have been structuring my operations linearly on the paper step by step. Do any of you have some tried...

Hello, How to find formulas for these$\displaystyle\int x^n\sin(x)\, dx, \displaystyle\int x^n\cos(x)\, dx,$ indefinite integrals when $n=1,2,3,4$ using differentiation under the integral sign starting with the formulas $$\displaystyle\int \cos(tx)\,dx = \frac{\sin(tx)}{t}...

The final result will only differ in its sign, but this is crucial. Having a positively, radially oriented electric field ##\textbf{E}##, I understand that the sign of the integral should be positive (## - (- A) = A##), but it is not! How and why is this the case? A line integral where the...

Why the sign change from < 0 to > 0?

What should I do? Because I have two possibilities. I have ##0=5+at## so ##-5/t =a##. But then I can also say that the acceleration is a negative because it is stopping, so I can write it like ##0=5-kt## and then ##5/t =k##

Hi all, I have a question on G-parity. I know it's defined as ## G = exp(-i\pi I_{y})C ##, with ##I_y## being the second component of the isospin and ##C## is the C-parity. In other words, the G-parity should be the C-parity followed by a 180° rotation around the second axis of the isospin...

Summary: Different sign in the combination of two ##\textbf{1/2}## isospins with opposite third component Hello everybody! I was doing an exercise regarding isospin and I noticed something from the Clebsch-Gordan coefficients that made me think. For example, if I consider the combination...

Hi everyone! I'm trying to understand why when writing the differential equation of a discharging RC circuit V_C-Ri(t)=0 \to q(t)/C - Ri(t)=0 we replace i(t) with -\frac{dq(t)}{dt}. I read many threads but I don't understand the physics behind this. The usual answers I read are something like...

##R_{X} = \sum F_{X}## ##R_{X} = 750.sin 60^{0} + 250## ##R_{X} = 899.52 N## to the right. ##R_{y} = \sum F_{y}## ##R_{y} = 750.cos 60^{0} - 1250## ##R_{y} = - 875 N## ##R_{y} = 875 N ## downward ##R = \sqrt {R_{x}^{2} + R_{y}^{2}}## ##R = 1254.89 N## ## tan θ_{X} = \large \frac...

$$W = - \int _ { a } ^ { b } \vec { F } \cdot d \vec { r }$$ ( The Force here is referring to the applied force, When moving a positive charge towards another positive charge(stationary) / field In this formula why there is a negative sign in the formula? I am not asking the sign of the total...

I have to find resultant for this couples: My sir resolved given forces into components like this: He considered Fx couples for sides 3,4,5 triangles: He wrote resultant force for this above diagram: ##\Sigma F_x = \textbf{-}2*\frac{4F}{5}##

Precursor : Sign conventions regarding Work by the system/on the system may even vary among Physics textbooks and among Chemistry textbooks and as a rule of thumb it is better to clearly mark out the convention used by the text being referred to specifically and remain consistent with it...

A 3 kg cafe sign is to be hung from 1 kg horizontal beam such that it is in equilibrium. The beam is 4 m long. A wire is attached to the beam at its right end to prevent the sign and the beam from rotating. The beam is pressed against the wall on its left end and is prevented from sliding by a...

What is the sign of phonon mass? A substance of uniform composition, in a field of gravity, has pressure increasing downwards. This causes the compressibility to decrease downwards - and speed of sound to increase downwards. In a gradient of downwards increasing velocity, a wave propagating...

We know that "plastic" and "glass" charges were arbitrarily assigned to be negative and positive respectively, and electrons and protons were given their charges based upon that assignment (According to Randall D. Knight in Physics for Scientists and Engineers). I am curious if any significant...

Hi, Is there a simple explanation for the presence of a minus sign in the Minkovsky´s metric? Best wishes, DaTario

Homework Statement I am revising on the derivation of the differential equation of energy (White's Fluid Mechanics 7th ed) and I'm having trouble understanding the sign convention used in the viscous work term. The textbook first define an elemental control volume and list out the inlet...

I am taking a high school multivariable calculus class and we have an end-of-semester project where we trace out some letters etc., except that they all have to be connected, continuous and differentiable everywhere. My group's chosen to do Euler's formula, but so far we are having problems...

While calculating the force between two charges , why we don't put minus sign with charge.

Is it true that if ##f## is differentiable at ##a## that ##f'(a) = \lim_{h\to a}\frac{f(a+h) - f(a)}{h} = \lim_{h\to a}\frac{f(a-h) - f(a)}{-h}##. That is, can the sign of ##h## be flipped. I've seen this a few times and it seems a bit dubious.

The electric potential can be defined as V = - ∫C E⋅dl where we are taking the line integral along C from some convenient reference point O, where we have set V = 0, to the point r we are trying to find the potential at. Of course, C can be any curve, but it's usually the most convenient to...

##\displaystyle \sum_{n=1}^\infty\frac{1}{n^2+n/2}## converges by the direct comparison test: ##\displaystyle \left|\frac{1}{n^2+n/2}\right| \le \left|\frac{1}{n^2}\right|##, and ##\displaystyle \sum_{n=1}^\infty\frac{1}{n^2} = \frac{\pi^2}{6}##. But what if we want to show that ##\displaystyle...

The question provides the vector field (xy, 2yz, 3zx) and asks me to confirm Stokes' theorem (the vector calc version) but I am trying to use the generalized differential forms version. So, I am trying to integrate \omega = xy\,dx + 2yz\,dy + 3zx\,dz along the following triangular boundary...

Hello! I am a bit confused about the sign of the ##L\frac{dI}{dt}## term in the circuits (DC circuits). In my book it is defined with a minus, on wikipedia it is defined with a plus and I am not sure which one should I use. I can pick any sign I want and the result will come out right...

Homework Statement Is the binding energy for a hydrogen like atom equal to the total energy (negative) or the negative of the total energy (thus positive)? 2. The attempt at a solution I found varying answers and definitions, some places said binding energy's the energy required to disassemble...

Homework Statement if ## f(x) ={\int_{\frac{\pi^2}{16}}^{x^2}} \frac {\cos x \cos \sqrt{z}}{1+\sin^2 \sqrt{z}} dz## then find ## f'(\pi)## 2. The given solution Differentiating both sides w.r.t x ##f'(x) = {-\sin x {\int_{\frac{\pi^2}{16}}^{x^2}} \frac{\cos \sqrt{z}}{1+\sin^2 \sqrt{z}} dz }+{...

Hi all, I've always regarded the coupling Hamiltonian for a bosonic cavity mode coupled to a two-level fermionic gain medium chromophore to be of the form, $$H_{coupling}=\hbar g(\sigma_{10}+\sigma_{01})(b+b^{\dagger})$$, where ##b## and ##b^{\dagger}## and annihilation and creation operators...

I am looking at a solution to an integral using differentiation under the integral sign. So let ##\displaystyle f(t) = \frac{\log (tx+1)}{x^2+1}##. Then, through calculation, ##\displaystyle f'(t) = \frac{\pi t + 2 \log (2) - 4 \log (t+1)}{4(1+t^2)}##. The solution immediately goes to say that...

What an amazing life and story! http://www.newsweek.com/koko-gorilla-sign-language-death-988302

I have the equation for simple harmonic motion ##\displaystyle \frac{d^2x}{dx^2} + k^2 x = 0##. I have a simple question. Do we need to make an assumption about the sign of ##k## before we solve this? We have that the roots satisfy ##r^2=-k^2##. So ##r=\pm i \sqrt{k^2}##. Do I need to assume...

For example F=ma means that the definition of force is m*a or the quantity of left side equals to the quantity of right side or both ? or kinetic energy..we know K=1/2mu^2 but is this the definition of kinetic energy or just the formula to calculate it ?

In the table of integral, there is this formula \int_0^{\infty}\frac{sin(ax)}{x}\,dx=\frac{\pi}{2}\text{sign} a is sign a here is literally the sign of a, or it means something else?

Homework Statement A carriage is mounted on a spring, as shown in the diagram. The bottom of the spring is fixed to the ground. The carriage (loaded with its passenger) has a mass of 150kg. The carriage can only move vertically. The natural length of the spring is 10m and its spring...

Homework Statement Hello, good afternoon, I have a question that's coming up when I'm doing electromagnetic induction exercises. In some exercises they ask me to determine the electromotive force (iee), and when they do the exercise resolution they do it with absolute value. In other...

Homework Statement Homework EquationsThe Attempt at a Solution I thought it would become d/dx(-kAc*dT/dx)+hp(T-T)=0 instead of where the equation in the red box? I don't see how are they equivalent [/B]

So we have the Newtonian gravitation potential given by ##\phi_M(r)=-GM/r##, and in class the teacher said that the Newtonian force is given by ##F_m = -m\nabla \phi_M(r)##. Now, I was thinking about what was taught in UG or high school, isn't the force should be ##F_m = GmM/r^2##, if I plug...

Energy of electron in nth Bohr orbit. En= -13.6 ev n2 what does this negative sign mean here ? and why the electron has less energy as we increase n ,, explain me with the help of electric fields and coulumbs law. :

Homework Statement I needed help to undestand some concepts in Ray Optics for my assignment. The topics which U am concerned are: Part 1: Mirror Equation, Refraction at singly curved surface, lens maker's equation, combination of thin lenses in contact. Part 2: Magnification Power of simple...

In the picture about, I gave 1. a picture of a segment of string for reference, 2. a description of the driving force and 3. a description about the potential energy per unit length of a point in the wave. I have two questions here. 1. Why does the driving mechanism produce a force to balance...

Good day ! I have an issue with the sign minus inside the skew bending (unsymmetric) formula First we all know that the stress generated by the bending moment is the following: and then after we have the formula I really don't understand why we don t have the sign minus in all the formula...

Homework Statement Two computer software packages are being considered for use in the inventory control department of a small manufacturing firm. The firm has selected 12 different computing task that are typical of the kinds of jobs. The results are shown in the table below. At the 0.05 level...

Homework Statement I know that for both method are used to test the 2 group sample for a non-normally distributed population ... But , i am not sure the difference between them . Can someone explain the difference between them ? When to use sign test and wilcoxon signed rank test ? Homework...

Homework Statement In the photo above , H0 = the position of the plant doesn't affect the number of seeds in the pods . H1 = position of the plant affect the number of seeds in the pods The Attempt at a Solution This is a two -tailed test , am i right ? Referring to the normal distribution...

I have seen the section sign \S mainly in legal documents. However, an acquaintance is writing a physics paper in which she uses this sign to refer to a section of another paper in which the section sign was not used (sections just being marked off by number), is it OK to use the section sign...

In ordinary mechanics, adding 1 particle to a system of 1000000 doesn't change a lot. I know about the sign problem in QCD, so when temperature is cold the amount of calculation diverges. My question is: when we add yet another quark to a system of 1000000 quarks, the amount of calculation...

A shop sign weighing 215 N hangs from the end of a uniform 155-N beam. Tension in supporting wire= 642 N Horizontal force exerted by the hinge= 526N Find the vertical force exerted by the hinge on the beam at the wall Fy= Fhy + Ft * sin() - mg - Mg =0 My attempt: Fhy= -(Ft *sin() - mg -...

Homework Statement ##y = \sqrt {x+5} + \sqrt[3] {\frac {x} {4}}## Find when the function is positive/negative/zero. We were actually supposed to only calculate the domain in this exercise, but we had done some simpler and more basic positive/negative calculations before, and I was curious...

Here the voltage is negative so the current is negative. does it matter if I traverse the circuit through the other direction?