All Questions
Tagged with potential-energy energy
69
questions
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Example in motivation for Lagrangian formalism
I started reading Quantum Field Theory for the Gifted Amateur by Lancaster & Blundell, and I have a conceptual question regarding their motivation of the Lagrangian formalism. They start by ...
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How is energy "stored in an electric field"?
My physics teacher told me the statement "The energy of a capacitor is stored in its electric field".
Now this confuses me a bit. I understand the energy of a capacitor as a result of the ...
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1
answer
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Feynman Lectures: Why a non-reversible weight lifting machine cannot lift higher that a reversible one?
Consider weight-lifting machines—machines which have the property that they lift one weight by lowering another. Let us also make a hypothesis: that there is no such thing as perpetual motion with ...
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3
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Coincidence, purposeful definition, or something else in formulas for energy
In the small amount of physics that I have learned thus far, there seems to be a (possibly superficial pattern) that I have been wondering about.
The formula for the kinetic energy of a moving ...
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6
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Why is potential energy negative when orbiting in a gravitational field?
I had to do a problem, and part of it was to find the mechanical energy of satellite orbiting around mars, and I had all of the information I needed. I thought the total mechanical energy would be the ...
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Lagrangian potential for Newtonian gravity
In the Wikipedia site for Lagrangian (field theory) the Lagrangian density for Newtonian gravity is given by
$${\cal L}(\mathbf{x},t) = \frac{1}{2}\rho(\mathbf{x},t)\mathbf{v}^2 -\rho(\mathbf{x},t) \...
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1
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Lower bound on energy is potential minimum
Suppose we have a particle of mass $m$ that is in an eigenstate $|\psi\rangle$ of the Hamiltonian $\hat{H}=\hat{T}+\hat{V}$, where $\hat{T}$ is the kinetic energy operator and $\hat{V}=V(\hat{r})$ is ...
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What is the energy of a single charge system?
I will try to limit the question in the case of the electric fields, but is something that applies also to the magnetic ones.
There are two ways to express the energy in a capacitor:
By Voltage : $U ...
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4
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Does work-energy theorem involve potentials?
According to khan academy,
"Net work done on an object equals the object’s change in kinetic energy. Also called the work-energy principle."
Now, here we see that there is no mention of '...
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5
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Heisenberg Uncertainty Principle Applied to an infinite square well
I appreciate the statement of Heisenberg's Uncertainty Principle. However, I am a bit confused as to how exactly it applies to the quantum mechanical situation of an infinite square well.
I understand ...
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Kinetic energy of the object, but Potential energy of the system: Why is it so?
Examples from Principles of Physics (by Walker,Resnick,Halliday) will say it better:
Let us throw a tomato upward. . .as the tomato rises, the work $\mathbf{W_g}$ done on the tomato by the ...
user36790
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1
answer
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Why doesn't the potential energy of any object equal 0
Consider a particle on the ground. This particle is raised by a force of magnitude $mg$ to a height $h$ above the ground. At this point, the work done on the particle by the force is $mgh$, which is ...
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Can the mass of a hydrogen atom be calculated in a gauge-invariant way?
Please excuse the lengthy question. It involves an interesting controversy which has arisen in discussions on this site:
Energy/mass of Quantum Vacuum
Relative potential energy vs Absolute potential ...
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4
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Potential energy and the work-energy theorem
So the title's a bit irrelevant. And I'm having a tough time thinking how to describe my doubt but I'll try my best. Apologies if it is vague, do let me know in the comments.
So I just finished ...
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Electrical potential energy stored in vacumm for a single point charge?
I have come to know the electrostatic potential energy in vacuum is given by
$${\frac{1}{2}} \epsilon_0\int d^3x {E^2} $$ and this energy is due to the mutual electrostatic coulomb potential energy.
...
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Bound states, scattering states and infinite potentials
I am doing my first semester of Quantum Mechanics and we're using Griffith's Introduction to Quantum Mechanics. As he is introducing the Dirac delta function potential he explains bound and scattering ...
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Has $E=mc^2$ been experimentally verified for macroscopic objects with potential energy?
In relation to this question: What is potential energy truly?, I'm wondering if $E=mc^2$ has been experimentally verified to hold true for macroscopic objects with increased potential energy? I'm ...
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Relative potential energy vs Absolute potential energy
I have seen in many textbooks and sources which say that we can't experimentally measure potential energy but we can measure differences in potential energy.
$$\Delta U_g=-W_g$$
Choosing zero ...
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3
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Why Energy is greater than min value of Potential in Bound state?
Griffiths describes bound and scattering states as follows:
Bound state : $E<V(-\infty $) and $V(+\infty $)
Scattering state: $E>V(-\infty)$ or $V(+\infty)$
Why is that Energy for a ...
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1
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Physics definition of work and lifting
My calculus text (Swokowski, Olnikc, Pence, 6th edition) gives the
formula for work as $W = Fd$ and then goes on to explain that if the
force varies over the distance the formula becomes an integral. ...
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3
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Work done by gravity on falling object does not seem to equal change in mechanical energy
So I have some confusion here, I am sure I knew this at some point. Let's say an object of 10 kg is dropped from a height of 10 m. When it reaches the ground, the work done on the object should be ...
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1
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Linking the work-energy principle with potential energy in the context of gravitational fields
I am trying to derive the equation for gravitational potential energy $E=-GMm/r$. On the Wikipedia page for energy:
https://en.wikipedia.org/wiki/Work_(physics)#Work-energy_principle it says that $W=-...
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2
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System of potential energy
Is potential energy calculated between a system? More specifically, if we say 'potential energy of a ball with respect to earth', does it mean that the Earth + the ball is a system?
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How is gravitational potential energy $mgh$?
I know the derivation that $W=Fd$, hence $F=mg$ and $d=h$ so energy gained by the body is $mgh$ considering the body on the ground to have $0$ gravitational potential energy.
But the definition of ...
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In physics sometimes we find energy that is negative. What does the negative sign indicate?
Sometimes we see energy that is negative, for example, the energy of an electron in orbit. We know energy is something that can do something. In this view does negative energy mean something opposite ...
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1
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Double counting potentials in $N$-Body Problem?
I suspect an error in my “Classical Dynamics” lecture notes but my lecturer doesn’t agree with me so I need your help!
We assume that in the $n$-body problem, the force between particle $i$ and $j$ ...
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1
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Why is the potential energy of a particle in a travelling wave maximum at the mean position?
I mean, we calculate the speed of a wave (in a string) by considering the tensional force as a centripetal one (that's obviously an approximation), so shouldn't potential energy decrease in the ...
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1
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Doubt in the expression of Lagrangian of a system [duplicate]
There is a problem given in Goldstein's Classical Mechanics Chapter-1 as
20. A particle of mass $\,m\,$ moves in one dimension such that it has the Lagrangian
\begin{equation}
L\boldsymbol{=}\...
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4
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How can we have negative work in electrostatics, if $W=(\epsilon_0/2)\int\! E^2\ \mathrm{d}\tau$?
This question is motivated by Section 3.2.3 in Griffiths.
Therein, we are considering the force of attraction between a point charge and an infinite conducting plane. One can calculate the field ...
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2
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Work done relation to potential energy
I know work done is negative of change in potential energy, I.e., $W=-(∆U)$.
It means that Work done against a force (or work done on a system) increases its potential energy.
And Work done by a ...
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