Homework Help

So my teacher, as we made the multipole expansion of Vector Potential (A) decided to proof that the monopole term is zero doing something like this: ∫∇'⋅ (J.r'i) dV' = ∮ r'i J ndS' = 0 The first integral, "opening" the nabla: J⋅(∇r'i) + r'i(∇⋅J) this must be equals 0 J = current density vector n = unit vector My question: I didn't get why the last thing (the nabla opened thing) was zero... He couldn't explain quite well and got confused, then the next day he added one condition to that be zero: [*] J is defined only in a certain region of space and that's why it's zero. I didn't get at all... *Sorry for my bad english

Hi, just needed some help in answering a past exam paper question which is as follows: "Draw the Radical Distribution Functions for 1s, 2s and 3s orbitals and point out the important features of these graphs". ​After looking through my notes the graphs which I found that correspond to the "Radical Distribution Functions " are : First question Is are these the right graphs? Even though they are titled "Radial Probability Functions (RPF’s)". ​Also there was no information regarding the second part of the question in regards to the "important features of these graphs." I tried looking online and was finding it hard to find anything, can anybody point …

Hello, I am a level seven student, and I would like to ask a question for my science project, and i did an experiment about the change in our body temperature after eating spicy food(and we choose the second most spicy noodles in the world ). The result shows that it actually lowered the body temperature, so I'd like to know why this phenomenon happens. I've done some research and i know that its because of sweating, but which body part produces/control/command SWEATING and some other information. So, i would like to know: -Which body parts -Whats Homeostasis -Whats Thermoregulation -Chemicals affecting body temperature -Capsaicin affect out temperature by? ~BRAIN…

Question: A sample of a compound of N and O reacts with excess H2 (g) to give 0.123g of NH3 and 0.325g of H2O. Determine the empirical formula of this compound. Been trying to solve it for a few days. My chem teacher wants the class (Grade 11 chem) to solve the questions on our own for prep for the unit test but no one else knows how to do this. I tried finding % composition to get to Empirical Formula but I got nowhere with it. I also tried doing mole ratios but I font have molecular mass of the unknown compound to find the mass of it. I think I need to get the balanced chemical equation but I don't know how to. Can anyone help me? Any hints? or where to star…

Hey every body.. peace be upon you. well i have to make a science project for our university science fair. i am thinking of making Discharge tube. can anyone guide me? how to prepare it... have you experience of it? or any other idea?/

Hi. I'm just a homeschooling mom teaching my son some basic botany. We did the potato experiment. After a number of weeks, some leaves grows from the eyes, But no roots was formed. I wonder what went wrong, or I need to wait more? Thanks

Do electrons revolve around nucleus because of centrifugal force or something else ?

I want to use the factor theorem to find the factors [math]2x^3+x^2-13x+6[/math] How do I do that?

Can [math]y^2-2xy-3x[/math] be factored? I tried to do it: [math]y^2-(2y-3)x[/math] [math]\rightarrow[/math][math]y(y-3)x-1(y-3)x[/math] and that finally gave me [math](y-3)x(1+y)[/math] Is this correct?

I need to find the stoichiometry between the reagents in order to find the theoretical yield. Please help I have no idea whatsoever how to do this.

I need help with this: I need some explanation when it comes to dealing with partial fractions. [math]\frac{7x+19}{(x+1)(x+5)}[/math] into simpler fractions.[math]\frac{7x+19}{(x+1)(x+5)}=\frac{A}{(x+1)}+\frac{B}{(x+5)}[/math] Why did[math]\frac{7x+19}{(x+1)(x+5)}[/math] become equal to [math]\frac{A}{(x+1)}+\frac{B}{(x+5)}[/math]?

Hello, my chemistry topic is all about Metallic substances and their properties. I read that Annealing (which is heating just below melting point and allowing it to cool slowly) causes the metallic grains to expand in size. Why is that? Like, does heating a metal decrease grain size or something? What does heating do the the metallic structure? We're not being told why it happens, we're told it just does. Please help.

In the attached picture, The reaction will go under certain mechanisms to give us the shown product , now to reach the final product we should know all reagents that help us to do the mechanisms. Can somebody help me actually there are 2 mechanisms.

I am posting in this subforum * because I do not know if this is actually the accepted theory (or one of them) and if I am just a slow learner..... This is my question.: Does mass and energy curve spacetime because spacetime , firstly is just a mathematical model with lines along parallel to the 4 axes that meet at all the points {x,y,z,t} that are the set of all possible events? In the real world (not the model) there are areas of mass/energy where "events" cannot take place because the "spot is taken" . As a result ,for the model to be accurate we have to make a "detour" ** around these particular areas when we draw the lines parallel…

Hey! So I've to write a 2000 word essay on the similarities and differences between Huntington's and Parkinson's regarding 'molecular pathology'. However, I've driving myself mad trying to understand this - given that there is so much information out there on these two disorders. I know I've to at least talk about the genes involved, CAG repeats, and Ubiquitin. Can anyone explain briefly to me where the difference and similarities actually lie between these disorders? Thanks

I have a theory question this time ... case 1 if I have two plates and theres a potential difference (p.d) across them 250 v ... an electron is fired from one end to the other end with some speed v m/s Case 2 Now I take the same plates same p.d however the plates are not uniform this time..... willl this have any effect on the speed of the electron? Compared to case 1 ... or will the time change?

Hello, I have a problem where I have a 1 dimensional Finite Difference Time Domain program simulating an electromagnetic wave, classically using Maxwell's Equations and the Yee Algorithm. What I would like to do is define an "effective" photon wavelength at every grid point (I don't know if it even makes sense to do so). The way I am trying to do this is; 1.) I have the electric and magnetic field magnitudes at every grid point: Ex, Hy (the simulation is Transverse Magnetic). 2.) I calculate the energy density of the wave at each grid point: EnergyDensity = ((Ex^2)+(Hy^2))/2 3.) I multiply the energy density by my spatial unit step cubed to get the total energy …

I am given the solution of NaCl and it has a mass of 53.2 g and a molar mass of 58.44 g. I already know to how to find the number of moles for the entire solution, but I also need to find the number of moles for Na + ions. How exactly to I go about doing that? Thanks in advance!

For parts A and B of this problem, use the following standard reduction potentials, free energies, and nonequilibrium concentrations of reactants and products: atp=3.1mM glucose=5.1mM nad+=350micro M Pi=5.9mM pyruvate=62 micro M nadh=15micro M adp=220 micro M co2= 15 torr half reaction NAD+ + H+ +2e- --> nadh E0 (V)=-0.315 2 pyruvate+ 6H+ + 4e----> glucose E0=-.590 pyruvate + nadh + 2H+ ---> ethanol + nad+ + co2 delta G' naught =-64.4kJ/mol adp+ h2o --> adp + Pi + H+ delta G'naught=-30.5kj/mol a) consider the last 2 steps in the alcoholic fermentation of glucose by brewers' yeast: pyruvate + nadh + 2H+ ---> ethanol + nad+ +…

I used the kinematic equations To first find mass from the k.e given And in the secound part I used the mass to calculate the new k.e .... I attached my working

My working is beneath question

I am literally clueless about this question.. the only thing I understand is the rate at which motor works implies power . And its rising at steady speed .so maybe the kinematic eq will come in handy.... how do I get started

the efficiency of a buffer in resisting changes in pH upon addition of base or acid is referred to as the buffer capacity. one way to define this quantity, which we shall call B, is B=dx/dpH, where x is the number of moles of base added to weak acid. Note that the HH equation may be rewritten as pH=pKa+ log (x/A0-x) where A0 is the total concentration of acid. obtain an expression for B, in terms of A0 and the fraction of acid titrated, f, where f=x/A0. hint: it's easiest to determine dpH/dx and take the reciprocal this is problem 14 in ch 2 of biochemistry ed. 4 the correct answer is B=(A0/2.303)f(1-f) I thought the answer was just to take the pH formula and u…

A 3.50 kg ball with a velocity of 10.00 m/s collides with a stationary ball with a mass of 5.00 kg. After the collision, the first ball travels at a 42.6 degree angle from its original path, while the second ball travels at a -26.7 degree angle from the other ball's original path. 1) What is the momentum of each ball after the collision? 2) What is the velocity of each ball after the collision?

And this time I have no idea even how to start the problem. I just know one thing I DIRECTLY PROPORTIONAL TO R^2 and the other formulae relating radius is given in the question..... now how to I relate both of them