Potential Definition and 1000 Threads

Hi! How do I check if the equation of motion of the particle, with a given potential, is invariant under time reversal? For a 2D pointlike particle with potential that is e.g $$V(x) = ae^(-x^2) + b (x^2 + y^2) +cy', where a,b,c >0$$ Can it be done by arguing rather then computing? Thanks!

What does the APD (Action potential duration) determine in a cardiac cell and how can it be changed (do I need to effect any of the phases of the AP)? For example, if the vagal nerve releases acetylcholine here are its effects: Inhibits Atrial Muscle Contraction- Negative inotropic effect...

Homework Statement Question: what rate does the water lose gravitational potential energy? Data: I have a pipe that water is flowing through and the pipe has 2 sections. In section 1: - the pipe is 11.9m above section 2 so, h = 11.9m - the velocity of water is $$v_1 = 0.3240ms^{-1}$$...

Hi, i need help in deriving the velocity potential of a moving 2D cylinder (circle) in potential fluid. The cylinder is moving in negative x direction U(t). I can derive the velocity potential of fluid past a cylinder (cylinder is stationary, in which it is the scalar summation of uniform...

Let's assume an electron and an anti-electron are in a gravitational field so they both have potential energy. What will become of this energy if they annihilate? Will the momentum of the photons after the annihilation will increase so the total energy will be conserved? Thanks for answering!

Homework Statement Two point charges Q1= +5.00 nC and Q2 = -3.00 nC are separated by 35.0cm. What is the electric potential at a point midway between the charges? Homework Equations V = Ke(q/r), PE = Vq[/B] The Attempt at a Solution This question is from Serway textbook. The answer is...

Homework Statement Determine the expression for the potential created by two magnetic monopoles (one positive, the other negative) that are equidistant from Earth's center (a/2 is the distant from each monopole to the Earth's center) and that are placed in the rotation axis. Homework Equations...

Homework Statement Two particles move in a central potential. The potential has the form V(r1, r2)=-a/(/r1-r2/^1.5)... Homework EquationsThe Attempt at a Solution I am having trouble understanding what it means for two particles to move in a central potential. From what I understand a central...

I have this simple circuit I know that if a consider the wire from the + of the battery until the + extreme of the resistor, in this portion the wire has the same potential. The same thing regarding the portion of the wire beetween the - of the battery until the - of the resistor. If this...

Homework Statement Homework EquationsThe Attempt at a Solution I think : the question means that almost all of the potential energy gets used into the explosion. If this is true then the potential energy gets reduced by ## \frac { GM^2} R ## or if the star just gets transformed into a...

Why the negative pole of a battery is said to be of higher potential? While if we a consider a DC battery of 12V (for instance) then we have Vpn=V (positive) -V (negative)=12V whish is a positive quantity, then we should conclude that Vp>Vn in contradiction to first statement! Please illustrate...

Homework Statement [/B]Homework Equations [/B] I = G * U The Attempt at a Solution [/B] Hello, i know the solution is 5.0 A/V but i don't know if my way of solving this was correct. I rearranged it to G= I/U and solved this equation for all the values in the table and then added them...

Homework Statement Homework EquationsThe Attempt at a Solution Using ## \nabla \times \vec A = \vec B##. I got that both ##\v A_1 ~~and~~ \vec A_2 ## produce ## \vec B##. So, the correct option is (d). Is this correct? [/B]

Homework Statement Homework EquationsThe Attempt at a SolutionChemical potential is defined as ## \mu = Gibbs potential per particle ##. So, is the system consists of N particles, ##\mu = \frac { G } {N } ##. Now, dG = VdP – SdT ## \frac {dG } { N } = \frac { VdP } { N } - \frac { SdT }...

Homework Statement Calculate the potential energy created by the spring in the mousetrap as a function of the angle the spring is pulled back. Homework Equations PE = ∫Fdx = ∫ kxdx = ∫k rΘ rdΘ ?? The Attempt at a Solution Is this a linear spring? we can use x = rΘ, and dx = rdΘ, so PE =...

I'm looking for a diagram or animation that shows the vector potential A (in the form of arrows or whatever) superimposed on the E and B fields of a plane EM wave. Since A is not unique, maybe two or three versions of the diagram (including one with Coulomb guage). An animation with a slider to...

Homework Statement A rotating magnetic dipole is built by two oscillating magnetic dipole moments, one along the y-axis and one along the x-axis. Find the vector potential at a point: (0, 0, ##z_0##) along the z-axis. Then find the magnetic field at ##z_0## . As the magnetic field is a function...

Homework Statement I've created code to crack a Hill Cipher (n=3). I'm unsure which cribs to try to crack a specific code. Would anyone mind posting ideas? The crib must be 9 letters in length. Homework EquationsThe Attempt at a Solution

Hi , this is my equation : μA= μA0 + RTlnaA A is the asphaltene in toluene solution . i want to calculate μA in different temperatures. where can i get μA0 and aA? tables? other equations? μA0 is the standard chemical potential of asphaltene and aA is the asphaltene activity in solution.

Homework Statement The probability for a particle of energy E<<V0 to penetrate a potential barrier of height V0 and width d is approximately \frac{16E}{V_0}exp\left[\frac{-2d\sqrt{2m(V_0-E)}}{\hbar}\right]. An electron moves between two potential barriers of height V0 and 2v0 that are of widths...

I am confused on where the gravitational potential energy is in this solution. Thank you

Hi, new member with a question that I might be asking wrong. A week ago I read an article or something on building a windmill generator, which I come back to every few years. So, this week, I was reading about how to calculate the voltage based on loops, turns, Teslas, area, RPMs and such, and I...

Homework Statement A proton is released from rest at the positive plate of a parallel plate capacitor. It crosses the capacitor and reaches the negative plate with a speed of 50,000 m/s. What will be the final speed of an electron released from rest at the negative plate? Homework Equations...

Hello. I've been watching Susskind's online Stanford lectures on classical mechanics to review the subject, and I believe he said that adding a constant to the potential energy does not change the action of a system. I see how it doesn't change the Euler-Lagrange equations and therefore...

The force constant of the spring in a child’s toy car is 550 N/m. How much elastic potential energy is stored in the spring if the spring is compressed a distance of 0.012m? The formula for spring force is F =kx When I do 550 x 0.012m I get 6.6 but I am supposed to round my answer four decimal...

1. With an elevation of 5334 m above sea level, the village of Aucanquilca, Chile, is the highest inhabited town in the world. What would be the gravitational potential energy associated with a 64.0 kg person in Aucanquilca? Assume that the free-fall acceleration at Aucanquilca is equal to that...

Homework Statement A particle that can move along the x-axis experiences an interaction force Fx=(3x2−5x) N where x is in m. Find an expression for the system's potential energy. Express your answer in terms of the variables x and the constant of integration C, where C is in joules. Homework...

Homework Statement 1D Potential V(x) = mw^2x^2/2, part of a harmonic oscillator. Suppose that the spring can only be stretched, so that the potential becomes V=infinity for x<0. What are the energy levels of this system? Homework EquationsThe Attempt at a Solution I argued my way though this...

Homework Statement The work done by an external force to move a -8.0 uC charge from point a to point b is 25*10^-4 Joules. If the charge was started from rest and had 5.2 * 10^-4 Joules of kinetic energy when it reached point b, what must be the potential difference between a and b? Homework...

Homework Statement An electron acquires 3.16*10^-16 J of kinetic energy when it is accelerated by an electric field from plate A to plate B. What is the potential difference between the plates, and which plate is at the higher potential. Homework Equations w =Δv * q The Attempt at a Solution...

Homework Statement Find potential difference between a and b in the figure Homework Equations Q=cv The Attempt at a Solution can anybody tell me how to apply the equation in this problem with more than one cell [/B]

I am confused how a charge could have negative work done. To clarify, I was doing a problem earlier in which a positive charge and negative charge are moving towards each other. I used the equation work = Δv * q And when I was doing this, the change in electric potential, Δv, was negative, and...

Assume a person is at space, and assume there's no friction or gravitational force in that space. The person has a bow and arrow. He stretches the arrow on the bow, and then shots the arrow out in the space. Since there are no friction and gravitational force in that space, the arrow will have...

Homework Statement I'm trying to figure out how to do D) and relate time to this potential energy graph. Homework Equations All I really know is that F = -dU/dx The Attempt at a Solution I tried to do something with F = ma and a = d2x/ dt2 and then set the - derivative of U(x) equal to the...

Homework Statement Two concentric cylinders with radii a & b (b>a) with an infinitely long grounded strip along the z-direction are given potentials \phi_1 and \phi_2. Find \Phi(r,\phi) for a<r<b Boundary conditions: \Phi(r,2n\pi)=0 \Phi(a,\phi)=\phi_1 \Phi(b,\phi)=\phi_2 Homework...

Here is problem I quickly made up: Suppose there is a ramp with a height of 6 meters and length of 12 meters. A block of 5 kg is pushed up to the top of the ramp with a constant velocity. The force of friction is 15 N. Here's the confusion: By using the non-conservative force work energy...

The gravitational potential energy of two massic points ##P_1## and ##P_2## with respective masses ##m_1## and ##m_2## is given by $$U = -G \frac{m_1 m_2}{|| P_2 - P_1 ||}$$ Now I was wondering how this formula could be applied to continuous matter. Let us imagine a very simple case where we...

I was answering the question, "Since electric potential is always proportional to potential energy, why bother with the concept of potential at all?" I answered that this is because Electric Potential Energy requires a test charge to calculate, Electric Potential is present without a test...

There is something that has been bothering me for some time about binding energy (and respective mass difference) but I was not sure how to formulate the question. Now it feels like I can ask it meaningfully enough. In GR energy produces gravity just like mass. But how potential energy is...

Homework Statement The problem is to take a small ball of mass m on a uniform rod of mass m which is hung on a hinge vertically downward, they're asking to find the velocity to be imparted for it undergo a complete rotation. I have the kinetic energy bit worked out but I'm getting the wrong...

Homework Statement A particle moving in a periodic potential has one-dimensional dynamics according to a Hamiltonian ## \hat H = \hat p_x^2/2m+V_0(1-cos(\hat x))## a) Express ## \frac{d <\hat x>}{dt}## in terms of ##<\hat p_x>##. b) Express ## \frac{d <\hat p_x>}{dt}## in terms of ##<sin(\hat...

Homework Statement In the system below, m1<m2. When the object of mass m2 has descended a distance h, the potential energy of the system has decreased by: Homework Equations the answer is (m2-m1)gh The Attempt at a Solution I used ΔU= Uf-Ui m1gh-m2gh=ΔU (I think that the decrease in...

Homework Statement A 1.00kg mass and 2.00kg mass are set gently on a platform mounted on an ideal spring of force constant 40.0 N/m. The 2.00 kg mass is suddenly removed. How high above its starting position does the 1.00 kg mass reach? Related to it... An 87 g box is attached to a spring with...

Is possible and what does it mean if a chemical potential is negative? I mean that for boson it means that in environment is "needed" boson (photon) and is possible to create him. Is it true? And what about for fermions? Could it mean that it is pleasent for environment to creat some fermion? Or...

Why is the potential of the Earth taken as zero ? Putting the question in other words:: All earthing is done to the ground. Over the years every singe charge in excess is grounded to the earth. Even then why is it so that the potential of the Earth is considered to be zero ??

Homework Statement A sphere of radius R has a volume charge density proportional to distance from center. Total charge contained in the sphere is Q. If electric potential at infinity is taken to be zero , potential at it's center is Homework Equations Here given are ρ= βr where β is a constant...

This is probably fairly simple, but I have a hard time to grasp the concept of the vector potential A in electromgnetism. Especially, in the following equation for the electric field : \vec{E} = - \nabla V - \frac{\partial \vec{A}}{\partial t} When does the second term is not 0 ?

Sorry if something is wrong... this is my first ever post 1. Homework Statement The Question: In one dimension, the magnitude of the gravitational force of attraction between a particle of mass M1, and one of mass M2 is given by: F(r)=GM1M2/r^2 Where G is a constant and x is the distance...

Recent discussions on pressure as a source of gravity and the related Tolman paradox have reminded me that few people seem to be aware that even in Newtonian gravity the pressure is related to the potential energy, which I've mentioned a few times on these forums before. This is easy to show...

Hi. I'm studying fluid dynamics and in particular potential flows. I know that for an irrotational flow the velocity field is a conservative field and it can be rapresented by the gradient of a scalar field v=-∇Φ. In this case the explicit form of Φ is something like a line integral between a...