Negative Definition and 1000 Threads

Hello! Homework Statement I want to evaluate the derivative of spherical harmonics with respect to the azimuthal angle and express it in terms of spherical harmonics.2. Homework Equations and 3. The Attempt at a Solution I have calculated the derivative of the spherical harmonic with respect...

Homework Statement This is the solution, the question was find its domain. Homework Equations How does |X| (less than or equal to) 4, when a negative number is inputed into -2x how does that = a positive number?The Attempt at a Solution On the graph to me All X values < 0 should be negative...

when a magnet is falling through a solenoid, voltage is produced. Once positive is produced and the when the magnet leaves the solenoid negative voltage is produced. Voltage is the energy lost by a unit charge when traveling from one point to the other. So if there is negative voltage...

Homework Statement When is electric potential negative and when is it positive? Homework Equations V=Es The Attempt at a Solution I first thought that when you are moving in the same direction as the electric field the electric potential will be a positive value. However I...

do negative charges in electric fields of positive charges have negative electrostatic potential energy? am I write in thinking they can't be at negative potential (V) because potential is a property of the field and has nothing to do with the charge in the field (like potential energy does)...

For when there is a negative test charge: The work done to get from infinity to r would be negative, corresponding to a decrease in potential energy so since dr must be a path element and therefore in the negative direction (towards the source of the E field) does that mean the...

Hi guys Is there any thing such as Negative Pressure, or is there only total vacuum 0 and nothing below that ?

Hello, i am doing an assignment and there is a research question that i need to answer. The question is: Can work be negative? From what i search on the internet these are my thoughts: Work is defined by W=F.D But work is not a vector, because it has units of energy and energy isn't...

Hi, This is a cascode LNA. Please help me with the question in picture. Thank you.

I could see that capacitor impedance is mostly negative. Does the negative sign has any significant meaning? Also why do people convert impedance to admittance for circuit calculation? Please help!

Why is one Tension Negative and the Other Positive -- Atwood Machines Hello, Please consider the following: I am trying to understand how to solve for acceleration when dealing with Atwood machines. I keep getting hung up on one part: the direction of tension. In the image above, why is...

is electric field strength always equal to negative potential gradient or can it be equal to positive potential gradient sometimes?

Homework Statement If a small positive and negative charge are created at rest at a point between electrodes as shown in the figure. In which direction will they move if one would neglect gravity? Ignore those weird arrows, those are for later questions. Homework Equations...

Recently, I watched a lecture with Alan Guth. He made an interesting statement. He said that to create an electric field requires work, because the like-charges prefer to repel one another, therefore this requires energy to bring them together. However; because gravity is attractive, it requires...

I have been learning that gravity has a negative energy associated with it. I've heard this stated a couple different ways, but I would like to understand a distinction. One line of thought declares that the potential energy of an object within a gravitational field is negative. Another line...

We know that gravitational energy is negative (zero energy universe theory). If the mediator particles (bosons) of the gravitational interaction are gravitons, then the energy of the gravitons would be negative?

I am using linear regression to predict 'y' based on 8 variables. With my example, most the Betas that I got are negative. So, y, the value to predict, is negative. To my data, y is a time in seconds, so I think it shouldn't be negative. I my example in python, and I want to know if y...

Hi this may sound like a simple question but I'm trying to find out the relative abundance of hydrogen in its various forms in space: H, H+, H-, H2, H2+, H2- I'd like to know these for our stellar neighborhood involving the solar wind and also for interstellar space outside the heliopause...

Hello. We learn that an NMOS is in the triode region for Vds < Vgs - Vth, and in this case the drain current has a given expression. My question is, is this also valid for Vds < 0 ? What happens in this case?

the potential energy of a earth-satellite system is -U. the kinetic energy of the satellite is K = -U/2. the mechanical energy M = -K. this is not true. the satellite is in equilibrium and the ∂θ change caused is limits to zero. the PE of the satellite cannot cause acceleration...

Owing to the Hamiltonian constraint in general relativity, the total energy is zero. (To avoid ambiguity, here energy is DEFINED as the corresponding part of the ADM Hamiltonian.) Since matter has positive energy, it implies that gravitational field has negative energy. Does it mean that...

Hi, In BIDMAS (brackets, indices, division, multiplication, addition, subtraction) it shows clearly that indices should happen before subtraction, so why does -52=25? Because the real working (according to BIDMAS) should put the square first and then put the negative sign on, which would mean...

Hi. I recently listened to a lecture by Alan Guth, speaking about cosmological inflation. He made the statement that the energy of a gravitational field is negative (followed by a great thought experiment with a collapsing shell of matter to demonstrate this). I am curious; does this mean that...

This article insinuates that the physics community had forgotten Gibbs entropy long ago and has used Boltzmann entropy since. Isn't this nonsense? For me it was always clear that Boltzmann entropy is problematic...

Can someone explain how these graphs are drawn. How does the value of p/q affect this graph? How does the domain and range change? How are the asymptotes found? The below is an image about what I'm talking about: Here is a question the deals with this type of graph (no idea how to solve it...

Hello, i'm looking for an explanation of a rule I used to solve a problem. I came to the correct answer in the end, but I do not understand why my first attempt went wrong. Homework Statement Find the general solution to cot4θ = tan5θ Homework Equations tanA = tanB => A = nπ + B...

Homework Statement Repeatdly roll a fair die until the outcome 3 has accurred on the 4th roll. Let X be the number of times needed in order to achieve this goal. Find E(X) and Var(X) Homework Equations The Attempt at a Solution I am having trouble deciphering this question...

Cathode rays are the flow of election, since electrons are -vely charged, is it normal for the rays to travel almost in a bundle without getting dispersed due to it's repulsion? If you say it's because of its velocity, then if you imagine each electrons, they are at almost rest to each other...

In a three phase power system,delta connected 66kV transmission line,the reactive power in one of the line/phase is negative(capacitive) while the reactive power in the other two lines/phases is positive.What is causing the reactive power to be negative(capacitive) in this phase?What are some...

I've been trying to figure out what a negative area means, but I can't. Homework Statement Calculate the area between f(x) = 3^{x} \, , \, g(x)=2x+1 The attempt to a solution The intersections are located in x=0 and x=1. So I do the integral from 0 to 1. \int_{0}^{1} (g(x)-f(x))dx =...

If yes, then for what values of n?

Undergrad studying engineering here, and my physics class has been doing a unit about intro to special relativity. Essentially, all of our problems and studies concern themselves with velocities which are in the +x direction relative to a "home frame" (I think physicists call this standard...

Hi, I am a math major in South Korea. Recently, one of my friends came to me with a rumor that age of the applicant is a critical factor in admission to top math grad school like princeton, harvard, etc... What worries me is that due to the country's "mandatory military service law ", I...

Homework Statement If you sum this from one to infinity. Ʃ (cos(1/(n)^2 - cos(1/(n+1)^2) Homework Equations The Attempt at a Solution Ʃ (cos(1/(n-1)^2 - cos(1/(n+1)^2) This is telescoping if you work that out for the partial nth partial sum you get cos(1) -...

Quantum mechanics has a well-known procedure for evaluating the expectation value of an observable quantity in a given quantum state. First one must obtain the quantum operator O that is associated with the observable quantity. Then the rule for computing the expectation value is: Apply O to the...

Why does the hydroxide ion have a negative charge? , i.e OH-?

What would it mean if in a power system with purely inductive and resistive elements (No Capacitance) if you were seeing a negative value of reactive power when there was no load connected? E.g. If the load was disconnected but the transmission line contained both resistance and inductive...

Hi MHB, I have encountered an interesting math problem which I couldn't solve. Problem: Find all values of http://www.artofproblemsolving.com/Forum/code.php?hash=86f7e437faa5a7fce15d1ddcb9eaeaea377667b8&sid=32778a5e32459cc05fd7472f968d6f64 such that $x^6-6x^5+12x^4+ax^3+12x^2-6x+1$ is...

How can a transformer have negative voltage regulation? A few texts state that a leading power factor can give rise to negative power factor, but I have not been able to figure out how this is possible. One vague explanation in my mind is that capacitance across the secondary terminal will...

Is it possible to create a graphite moderated light water cooled reactor w/ at least 3 GW thermal power output and a non-positive void coefficient that runs on slightly enriched uranium (0.9-2%) w/ at least 60 GWd/tHM burn-up? If not, is it possible to create a graphite moderated light water...

When using L'Hospital's rule to differentiate this function, why does the second term have a negative 1 multiplying it? Is it not already negative? Is it because of the -h in the expression?

How can we define negative work to be? I can't get my head around negative work or energy. However, I'm thinking that it must be work that is done opposite in the direction of motion of a particle or body (say, friction). Could someone please help me understand this concept?

when is g (9.8) negative or positive? i thought that g would be positive when its going towards the ground, and negative when it is being thrown in the air or against gravity.

Total energy is \frac{1}{2}mv^{2}-mgh=C for a classical non-rotating object right? C can be determined based on an arbitrary initial condition that suits the problem, right? How come it's not \frac{1}{2}mv^{2}+mgh=C? This seems like a more suitable definition of "total" energy. I'm sure there's...

Say there is a block that moves to the right. After a distance it hits a spring, and then it compresses the spring. Does this mean that the work that the spring does on the block is positive or negative? I would say it is negative because the block compresses the spring, so the displacement...

I have a problem understanding whether a sign should be positive or negative when it comes to a spring. In my book, there is an example with a glider attached to a spring, and the glider is moving away from the spring so it expands. It says that in order to use the work-energy theorem, it has...

The Title pretty much sums it up. http://en.wikipedia.org/wiki/Cyanide Why is it written like that when it is clear that the carbon must be the one with the negative charge?

Homework Statement Find the coefficient of x8 in the expansion of (x2-3)7 Homework Equations This one: (n n-j) an-jxj The Attempt at a Solution Hi! Well, I know that x= x2 a= -3 n= 7 and apparently, j=8. This is what confuses me. n-j is a negative number.. how would...

Are there such things as negative conductivities and/or resistivities in the real world? If so, what would these materials' electric characteristics be? This question is coming from my reading in an EM textbook where the EM wave equations are solved for a source-free, lossy medium (finite...

If two events separated in space by Δx occur simultaneously according to an observer S, then the time difference for S' moving at velocity u relative to S is \Delta t' = \frac{-u\Delta x}{c^2\sqrt{1-\frac{u^2}{c^2}}} Why is Δt' negative? \Delta t' = t'_2 - t'_1, where t'_2 corresponds to...