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Questions tagged [potential-energy]

Potential energy is the energy of a body or a system due to the position of the body or the arrangement of the particles of the system.

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19 views

Why are there 6 interactions with 4 positive charges?

From a homework assignment, there are 4 spheres spaced 1cm apart. Each of the spheres are charged to +10nC and weigh 1 gram. The question wants us to find the final speed of the charges once they've ...
13 views

Why energy is released (most of the time) when electrons are added to atomsg?

[Though initially the question may seem to belong to stack exchange chemistry but I believe that I would get a better physical explanation over here. ] Currently I was reading about electron ...
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Doubt in understanding the potential energy of dipole in external electric field?

When a dipole is placed in external electric field it experiences a torque $$\vec \tau = \vec p \ \times \vec E$$ whose magnitude is $$||\vec \tau|| = ||\vec p|| \cdot ||\vec E|| \cdot sin\theta$$ ...
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What is the three dimensional generalisation of a conservative force?

I was studying about conservative forces from a physics book (NCERT, a standard Indian textbook) and came to a para which is as follows: A force is conservative if it can be derived from a scalar ...
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Magnetic Dipole Moments and Dipole Contributions

I'm currently in Physics 2 (calc-based) at my University. On the last exam we had questions over magnetic dipole moments and dipole contributions. I'm still unable to solve these problems. Would ...
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Energy of the system of similar charges

We know that two same charges repel each other. To stop the charges from going away we have to exert an external force and hence energy is used. But if in a vacuum two similar charges are placed near ...
70 views

Can we detect a cyclic coordinate by just inspecting the Lagrangian?

I'm reading through Susskind-Hrabovsky's Theoretical Minimum. On page 126, where they are talking about cyclic coordinates, an example is given: Suppose two particles moving on a line with a ...
37 views

The energy stored in capacitors in series [on hold]

If there is a capacitor of $2$ micro farad and $0.5$ micro farad in series and the charge on the combination of the two capacitors is $0.8\times 10^{-6}$ C. How would you find the energy stored on ...
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Can I 'add potential together'?

I have the Lagrangian function for a particle in an electromagnetic field $$L = \frac{1}{2} m \dot{\mathbf{r}}^2 + q \dot{\mathbf{r}} \cdot \mathbf{A} (\mathbf{r}, t) - q \phi (\mathbf{r}, t)$$ If I ...
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On work done by internal forces which is coming out to be not equal to zero

1) Let us consider a block which explodes due to some internal mechanism into two smaller fragments of equal masses.The system was initially at rest and now is having some finite kinetic energy(due to ...
37 views

Strange factor of 2 in Hooke's Law [duplicate]

I was working on a PGRE practice problem: A brick of mass $m$ falls onto a masses spring with spring constant $k$ from a height $h$ above it. What is the maximum distance the spring will be ...
38 views

Why electric potential energy at a point is the same as amount of work done to bring the charge to that point from infinity?

Let's consider a positive charge at a point in the space. Now, if we want to bring a another positive charge to a point within the electric field of the first charge, then we have to do some work ...
30 views

Why potential energy of a non-relativistic particle in an expanding universe is $ma^2\phi$?

I have been reading a paper on neutrino clustering in an expanding universe: see section 3, particularly 3.3.2 of this paper. In this paper for non-relativistic neutrinos, which travel through a ...
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If voltage represents an energy difference between two points, why don't electronic appliances all use the same amount of energy?

As I understand it, voltage is an energy difference between two points. $$V_f - V_i = - \int \mathbf{E} \cdot d\mathbf{s}$$ But consider a toaster and a refrigerator each using their own 120V ...
14 views

Energy inside charged conducting sphere

We know that energy of a solid(or hollow) conducting sphere sphere is KQ^2/2r this energy is distributed from r to infinite and we say that energy inside is zero... Now we know that electric field ...
26 views

Virial theorem lmplies loss of potential energy

Learning equipartition theorem, I search related content on this web. But I stuck at some point when I look at this part: "However as we climb out of the potential well to large interatomic distances ...
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How to derive “a blob of water in space becomes a sphere” analytically? [duplicate]

I'd like to understand better the assertion that planets are spheres because of gravity. The thing which I believe is true, but don't completely get, is that any arrangement of a sufficient number of ...
40 views

Can I add a classical potential to S-matrix

I'm a junior learner of QFT, and I wonder if I can add a classical approximated potential (like Coulomb potential) to a total interaction \begin{equation}V=V_{\mathrm{Coulomb}}+V_{\mathrm{internal}} \...
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Central Potential + Coupled Angular Momenta

I am considering a two-state system with a Hamiltonian of the form $$H = \frac{p_1^2}{2m_1} + \frac{p_2^2}{2m_2} + V_a(|r|) + \bigg(\frac{1}{4}-\frac{S_1\cdot S_2}{\hbar^2}\bigg)V_b(|r|),$$ where ...
58 views

What is the maximum theoretical efficiency of conversion of potential energy to kinetic energy and vice-versa?

Am looking at different techniques available for identifying sources of energy. As part of it, have the following question : What is the maximum theoretical efficiency of conversion of potential ...
49 views

Conservative force as negative gradient of scalar potential

In Classical Mechanics by H. Goldstein it is mentioned that “To satisfy the strong law of action and reaction, $V_{ij}$ can be a function only of the distance between the particles $i$ and $j$, i....
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Spring mass damper system: Distance from equilibrium after applying velocity to mass

I have a spring fixed to a wall on one end and a mass object on the other end in its natural resting position. The question is how far does the spring stretch when a velocity $v_0$ is applied to it, ...
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Work Done and Potential Energy in Electrostatics

This is a question from class 12 Physics NCERT Part 1: I am having so much trouble with this, I can't figure out where I'm going wrong. I solved part (a) here: (a) U= -27.2 eV (b) Here, the kinetic ...
Conservation of energy says total change in energy is $0$. Let's assume a small object is in outer space (maybe like a football). It moves towards a planet (assume planet has no atmosphere for ...