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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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Is the given force conservative? [closed]

I've attached an image in which a question can be seen. I've successfully solved the problem and the answer is zero. However, I seek if the given force is conservative or non-conservative. I think it ...
Apoorva Shukla's user avatar
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3 answers
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Is gravitational potential energy of body by $mgh$ negative? [closed]

Consider a 15kg object at 1m from earth ground level, is P.E = 15kg * 9.8m/s^2 * 1m = 147J or P.E = -Gm1m2/r^2 * h = -9.8 * 15kg * 1m= -147J after browsing for a while on debate of potential energy's ...
Neptotech -vishnu's user avatar
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1 answer
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Why particle is certain to escape the conservative field when the mechanical energy is positive?

It is generally said that the particle is bound into the conservative field when the mechanical energy is negative and zero is the limiting case and the particle will escape the field when the ...
Het Patel's user avatar
1 vote
4 answers
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Explanation between the potential energy of a charge and the electric force experienced by a charge

Suppose there are two opposite charges and an infinite distance between the two. At this initial point, the electric potential energy of the two charges and the electric force experienced by each ...
12-CB09 Mayor Zander P's user avatar
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Force applied by hand, force applied by the spring and the corresponding work done

Consider a block of mass $m$ is attached to a massless spring of force constant $k$. If the spring is pulled by hand so that it stretches by an amount $x$, its potential energy increases from zero to $...
Solidification's user avatar
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1 answer
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Drawbacks of Quasi-Static process for lifting a block

Definition of Quasi-static: A quasi-static process is a thermodynamic or mechanical process that occurs very slowly, allowing the system to remain in a state of equilibrium at all times. While ...
Akhilesh G's user avatar
4 votes
2 answers
403 views

Spring potential energy, conversion

I have a physics problem in my book, where a spring is compressed and a ball is laying in the end of the spring. When the spring is released the ball will reach a certain speed. In the solution it ...
Ryan Johansson's user avatar
-1 votes
1 answer
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Strain energy stored in a bungee cord pulled at its midpoint [closed]

A bungee cord that behaves elastically has an unstressed length $L=.76$ m and a stiffness $k=140$ N/m. The cord is attached to two pegs, distance $b=.38$ m apart, and pulled at its midpoint by a force ...
Imperator's user avatar
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5 answers
106 views

When an object is thrown towards the sky it starts to gain potential energy, why?

I didn't think so because when an object is thrown towards the sky it already has kinetic energy and it looses it's energy due to the gravitational force of the earth. When the object looses all of it'...
Priyanka Bahadur's user avatar
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3 answers
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Question regarding gravitational force as external force

So, I was watching a lecture on YouTube for problems on conservation of energy and momentum and I don't quite understand this: In this question, mass $M$ is released from the peak of the smooth ...
Hrishikesh Pandey's user avatar
11 votes
3 answers
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Can a big mass defect make the mass negative?

Can two particles with small masses and a strong attractive interaction have a total negative mass when brought together? Let $m_1, m_2$ be the (rest) masses of two particles when infinitely distant. ...
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Getting an opposite sign for the centrifugal potential energy in the effective potential [duplicate]

Consider a system whose Lagrangian is $$L = \frac12 \mu\left( \dot r^2 + r^2 \dot\theta^2 \right) -U(r) $$ By the Euler-Lagrange equation, $$\frac{\partial L}{\partial\theta}=\frac{d}{dt}\frac{\...
xiver77's user avatar
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1 answer
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How Can there be a Gravitational Potential when there is NO Gravitational Field? [closed]

How does it make any logic that there exist a potential when there is no net field for example when we have a Hollow Sphere with mass we can find out the the gravitational *potential inside the sphere ...
Aditya Agrawal's user avatar
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4 answers
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Comparing Electric Potential Energy of two Charges

I do not know what I am missing here and would appreciate a little help in figuring out the flaw in my logic. I have a row of positive charges and a row of negative charges as shown in the image above....
Zeiglar's user avatar
1 vote
4 answers
75 views

Why is work done by force $+mgh$ in the situation of throwing something up?

If there is a particle at point A(at rest) and a force moves it to point B(Above point A vertically)(final velocity = 0 at this point), the work done by gravity is $-mgh$. This I understand as the ...
Gaurav Batra's user avatar
7 votes
3 answers
1k views

In equation (3) from lecture 7 in Leonard Susskind’s ‘Classical Mechanics’, should the derivatives be partial?

Here are the equations. ($V$ represents a potential function and $p$ represents momentum.) $$V(q_1,q_2) = V(aq_1 - bq_2)$$ $$\dot{p}_1 = -aV'(aq_1 - bq_2)$$ $$\dot{p}_2 = +bV'(aq_1 - bq_2)$$ Should ...
Bradley Peacock's user avatar
4 votes
3 answers
508 views

Why potential energy is not considered in the internal energy of diatomic molecules?

In thermodynamics, I am taught that there are 5 degrees of freedom in diatomic molecules since there are 3 for translational and 2 for rotational. I interpret degrees of freedom as "ways you can ...
bluesky's user avatar
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If I have a simple pendulum performing oscillations, whose string is snapped when it is at an extreme position, what will happen?

If I have a simple pendulum performing oscillations, whose string is snapped when it is at an extreme position, will it immediately fall vertically downwards because of gravity or will it continue ...
SuperSexyTrash's user avatar
2 votes
1 answer
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In which situation the potential energy of a system is equal to its Gibbs free energy?

The other day I was giving a presentation about Transition State Theory, and I was showing both pictures of some potential energy surfaces (PES) and some Gibbs Free energy vs. reaction coordinate ...
Nicoló Antonini's user avatar
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1 answer
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Self-Energy of a Conducting Shell based on Surface Charge Distribution

If a charge $q$ is given to a shell of radius $r$ (conducting or non-conducting) it's self-energy is $kq^2/2r$, $k$ being Coulomb's constant. But if the shell is conducting and the charge on the inner ...
JustAMathsGuy's user avatar
1 vote
1 answer
66 views

Why does the mass-energy equivalence apply to binding energy when it is derived purely through kinematic means?

I understand that by defining the four velocity, multiplying it by the rest mass and taking the entire thing's norm we get $E^2=m^2+p^2$, but how does this apply to binding energy, or in general ...
Y G's user avatar
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When is minimum potential energy in simple harmonic motion not zero?

We know that in simple harmonic motion, potential energy is minimum at the mean position and it is zero since displacement is zero. So what are some cases in which minimum potential energy is not zero?...
android's user avatar
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How is potential energy incorporated into mass in special relativity? [duplicate]

I've seen it said before that we often ignore potential energy in relativity because it can be included in the mass term. It is commonly said that a hydrogen atom has less mass than the sum of its ...
Aidan Beecher's user avatar
3 votes
1 answer
112 views

Confusions on The Gravitational Energy of a Point P in a Cube

I have been working, quite tirelessly, to try and find an answer to a question that has been bothering me for some time now. I have been working over some proofs, in the Newtonian Mechanics world, to ...
Statico's user avatar
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2 answers
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Rigorous definition of potential energy of a system

In the mechanics textbook by Kleppner and Kolenkow, the concept of potential energy is introduced by considering the behaviour of particle under the action of a force $\vec{F}(\vec{r})$ that depends ...
Vulgar Mechanick's user avatar
2 votes
1 answer
42 views

Momentum distribution of nucleons inside the deuteron (Paris potential)

I am looking for a graph that shows the momentum distribution of nucleons inside the deuteron. Side note: I know that several models for nucleon-nucleon potentials exist, such as the Paris, Bonn or ...
MCSquared's user avatar
2 votes
4 answers
188 views

Is the gravitational potential energy of an object on the ground 0? [duplicate]

In class, we were reviewing kinetic and potential energy and my teacher claimed that on the ground, objects have potential energy. However, as they cannot fall further, isn't their gravitational ...
user386598's user avatar
0 votes
1 answer
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What are the points to note in a spring+block system? [closed]

This is the solution to a question related to spring+block system, and I have some doubts regarding the concept behind this question The solution reads The velocity of the block increases till the ...
android's user avatar
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2 answers
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I am confused about potential energy and work done by a force [closed]

Potential energy is the energy contained in a body due to its position. But I don't understand it because when object falls, PE= mgh and work done by gravity, is - mgh. So what is the difference other ...
android's user avatar
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7 votes
7 answers
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Is it impossible to construct a Faraday cage that can block a *static* electric field?

I think the answer is yes. My reasoning is this: Imagine for argument's sake, we could have a charged negative source that has its field blocked by a Faraday cage. We can transport a positive charge ...
KDP's user avatar
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3 votes
0 answers
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A question regarding Coulomb sum in two dimension

The following arguments can be found in texts about Laughlin's wavefunction and theta function such as Laughlin's paper "Spin hamiltonian for which quantum hall wavefunction is exact". It is ...
fdsfsd sd's user avatar
1 vote
3 answers
56 views

Under what circumstances the work done by an external force gets stored as potential energy?

Consider earth and a block as a system. The block is accelerating downward under gravity. Now I apply a force against gravity which is less than the force of gravity. Would the work done against ...
Anvi Mahajan's user avatar
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2 answers
113 views

Paradox? Why does energy conservation appear to be violated in this simple geared system?

While answering a question about gears and levers, I found I could not get the work in to equal the work out in this simple gear system illustrated below: The gears are set up to replicate a lever, ...
KDP's user avatar
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2 votes
0 answers
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Energy of a spherical shell

System: spherical shell with surface density. Objective: calculate potential energy. I found energy through potential. Next, I found the formula for energy through the field, which gives two ...
neo's user avatar
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0 votes
1 answer
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Deriving expression for gravitational potential energy around a mass, $M$, using vectors

(I think my question will be somewhat related to this one: Deriving gravitational potential energy using vectors .) I know the change in the potential energy associated with a conservative force, $\...
Anis Manuchehri-Ramirez's user avatar
10 votes
2 answers
915 views

Is work done by a charged particle not gauge invariant?

Work done by a charged point particle with charge $q$ in an external electric field derived from a scalar potential $\phi$ is given by $$W=q \phi.$$ Even if we add a magnetic field the definition ...
user avatar
0 votes
3 answers
84 views

Why does my potential energy decrease when lifting a book?

I was reading morin's intro to mechanics book, and i reached the point where he was discussing work potential energy equivalence, which i find very confusing right now... basically we are analysing me ...
Aditya_math's user avatar
1 vote
1 answer
82 views

Electric potential energy, Electric potential and self-energy of a body

The total work done to bring all the charges constituting a body from infinity to the body one by one is called the electrostatic potential energy of the body. And if I divide the expression of ...
Peter swift's user avatar
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0 answers
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Gravitational binding energy of a sphere with radially-dependent density

As stated here, the gravitational binding energy of a uniform sphere is: $$U = \int_0^R -\frac{G}{r} \left(\frac{4}{3}\pi r^3\rho\right) \left(4\pi r^2\rho\right) \mathrm{d}r.$$ I want to know if the ...
Firestar-Reimu's user avatar
0 votes
1 answer
30 views

Apparent contradiction while calculating potential inside shell due to off center charge

Consider the following scenerio$-$ A point charge $Q$ is placed at an off center point $B$ in a spherical shell made out of a conducting material. We are required to find the potential at the center. ...
Eisenstein's user avatar
0 votes
2 answers
28 views

Body's energy before and after thrown into space

Suppose a body is thrown out in the space with a velocity greater than its escape velocity. Now from conservation of law its said that the kinetic energy is converted to final potential energy. So ...
Questioningmind's user avatar
1 vote
0 answers
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Why doesn't net work equation take the change in potential energy into account? [duplicate]

I know that $$\text{net work} = \text{work done by conservative forces} + \text{work done by non-conservative forces}.$$ and $$\begin{split}\text{net work} & = \text{change in kinetic energy} + \...
Rohan Rajasekar's user avatar
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1 answer
58 views

Question about Problem $12$ in Chapter $11$ from Kibble & Berkshire's book

I write again the problem for convinience: A rigid rod of length $2a$ is suspended by two light, inextensible strings of length $l$ joining its ends to supports also a distance $2a$ apart and level ...
panos Physics's user avatar
1 vote
1 answer
73 views

Quantum Harmonic Oscillator With a Linear "Perturbation"

It is well known that the energy solutions for the unidimensional quantum harmonic oscillator $V(x) = \frac{1}{2}m\omega^2x^2$ are $E_n = (n + \frac{1}{2})\hbar\omega, n \in \mathbb{N}$. In particular,...
Victor Lins's user avatar
0 votes
1 answer
44 views

What is the physical significance of this generalised potential?

Consider a generalised potential of the form $U=-f\vec{v}\cdot\vec{r}$ where $f$ is a constant. This potential should not contribute any internal forces between particles as \begin{equation} \vec{F}=-\...
Rescy_'s user avatar
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0 votes
1 answer
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Clarification on bound states: do "locally bound" states exist?

In Griffiths, a state with energy $E$ is said to be "bound" if $$E < \min\left(\lim_{x\to\infty} V(x), \lim_{x\to-\infty} V(x)\right)$$ (i.e. $E$ is less than both of those quantities). ...
Trisztan's user avatar
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1 vote
1 answer
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Feynman Vol.I 4–2 "Gravitational potential energy": a little confusion in the elegant proof

I'm new here and I've been reading through Feynman's great lectures from the very beginning. In Feynman Vol.I 4-2 "Gravitational potential energy", Feynman uses an elegant proof to show the ...
gžd15's user avatar
  • 111
1 vote
1 answer
130 views

Why can we ignore the work done by gravity?

I am working through the problem above, starting with part (d). By the conservation of energy setting the spring in equilibrium as $y_0$ as the difference in length of the unstretched spring to the ...
Chris Christopherson's user avatar
0 votes
2 answers
41 views

Where did potential energy disappear in this case?

Just a new thought experiment. We know that the kinetic energy depends on frame of reference as do work and velocity. Now we can consider a falling ball. It converts potential energy to kinetic energy ...
Hazim Ahmed's user avatar
0 votes
1 answer
77 views

Doubt regarding proof of Earnshaw's Theorem using Gauss's theorem

While proving Earnshaw's theorem using Gauss's theorem, we consider a small sphere surrounding our test charge, and apply Gauss law on this sphere, stating that field from all external charges must ...
Eisenstein's user avatar

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