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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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At infinite separation do charges get kinetic energy?

When charges are infinitely separated, the potential energy is reduced to zero. As we know that loss in potential energy is nothing but the gain in kinetic energy . So do charges start flowing at ...
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How Do I Calculate the Potential of System?

I was doing my homework when I came across this question: Three equal point charges, each with charge 1.40 μC , are placed at the vertices of an equilateral triangle whose sides are of length 0.250 ...
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Formula manipulation [on hold]

What is the potential energy of a metric ton (1000 kilograms), 3 meters above Earth's surface (at sea level), expressed in Kilowatt Hours? Assume that the mass will end travel when it contacts Earth. ...
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Gravitational potential energy of an isothermal sphere

I am trying to calculate the gravitational potential energy, W, defined as: $W = -\frac{1}{2}\int\rho(r)\Phi(r)d^{3}r$ for an isothermal sphere. I am given that the density profile varies with r as:...
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Gravitational potential of an infinite plane

In this link http://www.feynmanlectures.caltech.edu/I_13.html#Ch13-S4 , Feynman first computes the gravitational field generated by an infinite plane of constant density, and then he computes the ...
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Nonlinear GPE of a solid block seems wrong

I am trying to calculate the gravitational potential of a solid block, and I have a nonlinear answer which strikes me as wrong. A block with horizontal surface area $A [m^{-2}]$ and uniform density $\...
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Why is there no negative sign in the formula of work against electric field?

Why is there no negative sign in the first formula of work done against electric field where as second formula below has it?
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Vector calculus simplification in calculation of generalized force

Consider a system of $N$ particles subject to forces $\vec F_i\ (i=1\dots N)$ that derive from a potential $V$. My lecture notes propose a simple proof that $$Q_j = -\frac{\partial V}{\partial q_j}$$ ...
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What exactly makes negative energy negative?

Antimatter is the opposite of matter since it has opposite electric charge (e.g. proton -> positive whilst anti-proton -> negative). So what exactly makes negative energy negative? What property does ...
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What does 6v mean? [closed]

Though not related to the topic a gravitational field strength will tell how strong the field is or how fast an object will change its velocity when in this field. The same way what does it mean to ...
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The formula of voltage

Definition from Wikipedia: An electric potential (also called the electric field potential, potential drop or the electrostatic potential) is the amount of work needed to move a unit of positive ...
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Why does the potential along a uniform current-carrying wire vary with the distance along it?

Is it because as the electrons move further through the wire they lose more energy due to resistance? Also, in this context, I believe potential refers to the electric potential energy but I am unsure,...
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Moving a charge and potential energy

When talking about bringing a charge from a reference point to another point, we consider the work done by an "operator" force opposite to the electric one, but wouldn't that just cancel the ...
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Weight and potential energy for a spring pendulum

Consider a spring pendulum like in this figure suppose the spring is arranged to lie in a straight line and its equilibrium lenght is $l$. Consider the unit vectors $e_1, e_2$, $e_x, e_{\...
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Doubts about interpretation of the curves of effective potential energy

The image shows a graph of the effective potential energy. Where,$K=-Gm_{1}m_{2}$ and $L$ is the angular momentum. The graph of the effective potential energy that can be seen in this publication was ...
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Rotational potential energy on a system of two masses

On a homework assignment, we were given the following problem: This system is held at equilibrium according to the configuration in the image; initially the body B is at rest, and the body A is ...
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Can Potential Energy be found by Energy Density? [closed]

I wanted to find a creative solution to the problem: Find the electric potential energy of a uniformly charged sphere of radius $R$ possessing a charge $Q$. My attempt at a solution: Consider a ...
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Battery operation, charge and discharge processes misconceptions

I'm trying to elaborate a simple and concise explanation (and conceptually correct) of how a battery charges and discharges, and why we say things like "the charge stored in the battery is x Ah". For ...
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Potential energy requirements for the Lagrangian to work

It's clear to me that in acquiring the equations of motion using the Euler-Lagrange equations and the Lagrangian, defined as $$L \equiv T - V,$$ the potential energy may have a time dependence if the ...
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Electric potential energy of charges localized to the surface of an object

For a 3D object with a uniform density of surface charge, is there a particular shape which minimizes the total electrical potential energy? For instance, one could consider an object of fixed volume ...
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Object System and Potential Energy [closed]

I know that the object system doesn't incorporate PE due to gravity, but does the object system usually include PE due to springs or other factors, or is the object system exclude all PE and you would ...
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Rocket Leaving Earth's Gravitational Field

I stumbled across this seemingly simple question that really stumped me on further thought: A rocket is intended to leave the Earth's gravitational field. The fuel in its main engine is a little ...
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Classical period of Morse potential [closed]

A particle of mass $m$ and energy $E<0$ moves in a one-dimensional Morse potential: $$V(x)=V_0(e^{-2ax}-2e^{-ax}),\qquad V_0,a>0,\qquad E>-V_0.$$ From the only other question I ...
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Why do physicists take the convention that a force field is the negative gradient of a scalar field?

A conservative force is naturally the vector gradient of a given scalar field . I don't know why the convention to put the negative sign in front of the gradient operator. Or is this just a ...
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Does this example contradict Earnshaw's theorem in one dimension?

This is basically a continuation of the post here. Consider electrostatics in $1$-dimension (say, the $x$-axis). Now consider a positive charge $+q$ located at $x=0$, and two equal negative charges $...
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How can i derive the potential energy density of a sound wave or any longitudinal wave?

I have been trying to derive the energy density( potential energy per unit length) relation for a sound wave. I tried to find the work done in compressing a volume element as negative of that must be ...
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Potential energy of an oscillating pendulum

The following question always confuses me. for an oscillating pendulum why the potential energy is given by: $$V = mgL(1-\cos\theta)$$ Why not $$V = mgL\cos\theta$$ Is this a convention or there ...
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Work kinetic energy theorem

I don't understand the wordings of this theorem. Can someone please help me in understanding this? Secondly on what basis are the sign conventions in this theorem applied? I get confused in plus and ...
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Potential Energy in conservation of energy [closed]

In energy conservation theorem, everywhere $PE=mgh$ is used. What I found is that change in PE= mgh. According to me, while calculating total energy, instead of change in PE, total PE should be used ...
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Gravitational Potential Energy between points on a disk

So if I wanted to calculate the potential energy between two points on a disk, would I just use the formula for Gravitational Potential energy? if so, what would be the mass? Would I use some form of ...
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Difference between voltage, electrical potential and potential difference

I am having hard time to visualize these two concepts in my mind seriously. First of this confusion came from two parallel plates that was connected to a power supply, charged then disconnected from ...
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If I have a mass on a spring does it change it's rest length?

If, for example, I have a mass on a spring that compresses it of a length x. If I compress the spring more of a length y, when I release the spring the kinetic energy of the mass would be $\frac12 ky^...
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How Work =Voltage * Charge? [closed]

We know, Work/charge=volt So work =volt*charge But work =Fd So my question is since both voltage and charge are not dependable on distance,so how come work can be calculated without factoring in ...
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Work done against gravity in climbing and partially descending a wall

A question I found in a book recently concerned two worms climbing up one side of a wall and back down the other side, such that the worms were each half across the wall (I.e. the lengths on either ...
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Is this statement true for all conservative forces or just attractive conservative forces?

'Change in potential energy is always equal to the negative of the work done by a conservative force.'
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Question about multipole expansion of electrostatic potential?

If I take a certain dipole and by dipole I mean that two charges of opposite sign differentiated by very small distance. And if I take the formula of multipole expansion of potential then I see no ...
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Doubts in understanding the elastic property of matter

Here the graph of potential energy and force produced due to interaction between two atoms are given . And at a particular separation between the atoms, they have their minimum potential energy. And ...
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Potential Energy and Antimatter anihallation

Apologies if I've misunderstood anything fundamental, but the following has been on my mind for a while: Imagine the following scenario: Take two matter objects of identical mass etc. Now one is ...
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What is exact definition of potential energy if all forms of energy except kinetic comes under potential energy? [duplicate]

I need to know the exact meaning of potential energy. I AM confused what it actually means.They say all types of energy comes under 2 types kinetic and potential so what is potential energy then? My ...
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How can a system of Atwood machine lose gravitational potential energy?

The heavier block in an Atwood machine has a mass twice that of the lighter one. The tension in the string is 16.0 N when the system is set into motion. Find the decrease in the gravitational ...
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Can we define potential for all conservative forces?

I know that defining potential for non-conservative forces is not possible and we can define potential and potential energy for conservative forces only. But can we define it for all conservative ...
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Spring force potential energy and work done

Is the work done by external constant force = to potential energy stored in the spring. i.e. $Fx=\tfrac{1}{2}Kx^2$ But we know $F=kx$ but then $Fx = Kx^2$
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Quantifying potential energy

As per the definition of potential energy we kept a fixed charge, and in the presence of an electric field of the fixed charge, we release another charge of the same sign moving towards the fixed ...
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Doubts in understanding some concepts of potential energy

Let us consider a system of charges in space. The potential energy of the system of charges is determined by the amount of work done by the external force to assimilate the charges in that manner. But ...
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Why is the mechanical energy lost whenever an object undergoes plastic deformation?

I have read here that "Mechanical energy is lost whenever an object undergoes plastic deformation." Why is that? I mean the object would be changing its shape, and while it's changing its shape it ...
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Potential Energy equation is wrong as $mg$ force acting upwards (by us) and gravitational force ($-mg$) get cancelled and no movement is possible [duplicate]

In physics, the potential energy of an object is mgh. We say that the potential energy of an object is equal to the work done on it to make it reach that height. So the work done = mg h. Mg is the ...
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Potential, Kinetic, Thermal Energy?

When things move, potential energy turns into Kinetic energy, right? Then how does Kinetic energy convert to thermal energy?
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Why isn't electric potential infinite?

In my textbook, I've read that electric potential is the work performed to carry one unit of positive charge to electric field from infinite distance. We know that, W = Fs So here the distance is ...
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How is the velocity field of a fluid related to conserved quantities?

In multivariate calculus classes you learn a theorem that says that "A vector field is the gradient of a potential function on a domain $D$ if and only if it's curl-free on $D$." When I try to apply ...
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Potential energy of ice cube is container dependent?

The potential energy of an ice cube floating at sea can be measured from the surface of the water, which remains at a constant height as you drop the ice. However, what about when you drop it into a ...