All Questions
Tagged with energy potential-energy
480
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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 ...
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2
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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?...
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30
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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 ...
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2
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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 ...
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113
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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, ...
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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 ...
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2
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41
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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 ...
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2
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Shape of graph of energy in S.H.M
I'm confused to whether the graph of KE/PE of a simple harmonic motion system is sinusoidal or not
those are my best sketches but if unclear, the blue one is in a shape of a sine wave.
this question ...
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Question related to conservation of energy
Here is a textbook passage that I have trouble understanding. It is taken from Classical Mechanics by Tom WB Kibble and Frank H Berkshire.
We consider first a particle moving along a line, under a ...
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If a 100,000 ton container ship slams into a bridge at 8.6 knots how much energy was moved into the pylon and at what rate of transfer speed? [closed]
Edit: the entire question is in the title, the answer should be an amount of energy and a value of energy transfer in some unit, but not knowing enough about physics I don’t know what the appropriate ...
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2
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74
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Energy in different coordinates in central force motion
With reference to central force, we see that K.E has 2 terms in 2D cartesian cordinate but just 1 term in polar coordinates and potential energy has 1 term in cartesian but 2 terms in polar.
Basically ...
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2
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Does mechanical energy means total energy?
I know that mechanical energy is the sum of kinetic energy and potential energy. But there is a sentence in the book like this:
'Our primary goal, however, is to find the energies associated with ...
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58
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Energy in electric field of an electron?
I am just trying to get an intuition for the Griffiths equation no. 2.45, where work done to establish a field E is given by
Say we want to solve it for electric field due to an electron (point-charge)...
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69
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Why does the total gravitational potential in the universe exactly equal the total mass energy RIGHT NOW? [duplicate]
In the zero energy universe model, the gravitational field has negative energy, and this negative gravitational energy of all the distant mass exactly balances and cancels the positive mass-energy in ...
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Change in Work-Energy Theorem
We have Work-Energy Theorem as follows:
$$W_c +W_{nc} + W_{ext} = ΔK$$ $-(1)$
, where $W_c$ = work done by conservative forces,
$W_{nc}$ = work done by non-conservative forces, $W_{ext}$ = work done ...
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4
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When is the internal energy of a system not considered potential energy? [duplicate]
I have seen the total energy of a system, $E$, given in two forms:
$$E = K + U$$
where $K$ is the kinetic energy and $U$ is the potential energy, as well as
$$E = K + U + I$$
where $I$ is the internal ...
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Work and Energy Theorem - Theoretical Question
The work energy theorem states that for a given object
∆ Kinetic Energy = Work done by all forces ( Conservative, Non Conservative, External )
Here ,
Suppose if ∆KE = 0 , Potential energy has changed
...
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Direct conversion of potential energy into heat
Is it possible for potential energy to be dissipated (converted into heat) without being first converted into kinetic energy? Put differently, are there isolated systems at complete rest which turn ...
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2
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Does infinite time dilation increase a photons energy to collapse to a black hole, and does it do the same for matter?
As I understand the mass of an object doesn't increase in a gravitational field according to general relativity. It just follows a geodesic, its worldline.
Now imagine a small marble falling straight ...
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How do you calculate the potential elastic energy in only one of the springs of a series? What about if they were connected in paralel? [duplicate]
Given the elastic constants of 2 springs (k1=125N/m, k2=200N/m), how can you calculate the ratio between the potential elastic energy stored in the first spring (k1) when it is grouped in series with ...
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3
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134
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Why do things always want to reduce their energy? [duplicate]
Every object wants to reduce its potential energy, but why is that so? Does it have an explanation, or is it just a law we accept?
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If a car is *accelerating* uphill, does it *gain* kinetic energy?
I had an exam yesterday on physics (9th Grade), there was a question that confused me a lot. It said: "If a Gas Car is accelerating uphill, what happens to its G.P.E and K.E?"
A: It loses ...
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Conservative force and change in the mechanical energy
Why is work done by a conservative force equal to change in the potential energy only? Why doesn't it account for all mechanical energy, what about kinetic energy?
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Negative Energy [duplicate]
I am uneducated on physics so please excuse my ignorance. I've been looking into negative energy which hasn't made much sense to me thus far. Through what I've read I think negative energy is simply ...
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Why doesn't voltage increase when the wire length increases; there's more work to be done?
This Q&A did not answer my question.
The voltage of a circuit is the difference in each Coulombs potential energy at the negative pole, compared to the positive pole. At the negative pole, there's ...
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Is the Kinetic minus potential energy the only type of Lagrangian function? [duplicate]
In Landau-Lifshitz's "Course of Theoretical Physics - Mechanics"
It is told that a lagrangian is a function $\mathcal{L}$ such that the action $S$, defined by:
$$S=\int_{t_0}^{t_1}\mathcal{L}...
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74
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Is potential energy a real form of energy? [duplicate]
Is potential energy a tangible form of energy that an object possesses due to its position or configuration, or is it simply a concept used to estimate how much energy an object will have in the ...
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48
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Work And Energy: Conceptual Potential Energy Doubt
Our teacher told us that objects store potential energy in them according the position of the object above the ground because of gravitational force.
Like we are holding a box up and it stores ...
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2
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120
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Potential energy of external force
The potential energy is a property of a system, being defined only for internal conservative forces. From the work energy theorem, we have
$$W_{ext} + W_{\text{internal cons. forces}} = \Delta K $$
We ...
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3
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How does gravitational potential energy work in a very large distance?
Consider a thought experiment (that I made when I was in high school) involving a universe with only two objects: a massive planet and a small asteroid. Initially, they are millions of light-years ...
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Violation of energy conservation due to Lorentz Force?
We know that work done by Lorentz Force $q(\vec{v}\times\vec{B})$ is $0$ on moving charge in magnetic field as velocity is always perpendicular to the force. This means that kinetic energy remains ...
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189
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Where does an object get its energy from and what does it mean?
It is stated that an object in motion acquires "kinetic energy" while an object under the influence of gravity when raised to a height acquires "potential energy" but I have a ...
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6
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287
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Does potential energy actually exist? Or is it just a useful mathematical model? [closed]
The title basically covers it. I've actually thought about this question for a while now, and I am still not sure if I have a definitive answer. Most potential energies seem to just be the work that ...
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Why Doesn't the Amount of Work Determine the Elastic Potential Energy in Springs and Gravitational Potential Energy? [closed]
Why isn't the amount of work done on the spring the determining factor for the amount of elastic potential energy stored in a spring?
I learned that the change in potential energy is a result of the ...
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Potential energy separately for each object
Potential energy change is :
$\Delta U = -W_{int}$ where $W_{int}$ is the internal forces.
For the ball which is falling down towards earth, we can write:
$\Delta U = -(W_{earth} + W_{ball}) = -(K_{...
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Elastic potential energy formula
From the Wikipedia page on elastic energy, we can find a bunch of formulas to describe it. For example, in the continuum section it talks about energy per unit of volume (density?):
$U=\dfrac{1}{2}C_{...
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106
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Change in potential and kinetic energy after a photon is absorbed by a electron
This is a question from the AP Physics 2 2022 FRQ. Why does the potential energy of the atom and the kinetic energy of the electron decrease after a photon is absorbed? Shouldn't both of them increase?...
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143
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Potential energy density of a fluid in motion
If I have a fluid in motion at a given time and I know its pressure $p$ everywhere, I know its dynamic viscosity $\mu$ and I know its velocity field $\vec V$.
This system must hold some intrinsic ...
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Force in the Casimir effect
In the Casimir effect, after performing the regularization, it is found that the zero point energy between two conducting plates in a distance $L$ from eachother is (in the 1D case),
$$E=-\frac{\hbar ...
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2
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Work done by gravity confusion
Say we had an object at height $h$ in a gravitational field, and of mass $m$, its GPE would equal $mgh$, now say we dropped it and it fell a distance of $h$, the work done on the object would be equal ...
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4
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Circular reasoning involving conservation of energy and the definition of potential energy? [closed]
This might seem a dumb question but it is at the heart of mechanics.
We learn that in our universe the total energy of a closed physical system is conserved, never destroyed, never created, only ...
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Equilibrium of a body with potential energy as a function of position
We know that if the potential energy of a body, say $U(x)$ of a body is known as a function of its x-coordinate, for equilibrium, $$\frac{dU(x)}{dx} = 0$$ Also, several sources suggest that for the ...
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Where does the energy goes if the force is parallel to the displacement? [duplicate]
So, we all know that if force is perpendicular to the displacement, then work done is 0. But to generate force, I have to use up some of my energy. Had the angle not been perpendicular, my energy ...
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2
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286
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Shouldn't the electric potential energy decrease with separation regardless of whether the charges are positive or negative?
I was revising Electric Fields and it came up that if a positive charge moves in the direction of the electric field (so away from a positive charge), then the electric potential energy will decrease ...
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Energy in electric field calculated in two different ways
The equation for the energy density in a region of space where there is electric field, $\epsilon_0E^2/2$ implies that energy in the electric field can only be positive. Consider, however, the energy ...
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First principle of thermodynamics with kinetic and potential energies
Edit: Sometimes the first principle is stated as $Q+W=\Delta U\;+\Delta K\;+\Delta P$ (1). I assumed that the expression comes from the more elementary principle $Q+W_{total}=\Delta U$. On the one ...
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88
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Consolidating two ways to calculate work
I was wondering if I could get some help closing some fundamental gaps in my intuition of work, as it relates to force and distance travelled.
Scenario
Say we pull a 1kg box along the ground. We pull ...
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235
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How to derive bound and unbound states for an absolute value potential?
How do you find for what range of energies the absolute value potential has bound and unbound states?
What I have understood from my previous Intro to Quantum lectures are that in order to derive the ...
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Kinetic and Potential Energy of a multi degree of freedom (MDOF) system
Consider the following MDOF system:
$M\ddot x+Kx=F$
where $M$ and $K$ are the mass and stiffness matrix respectively, and $x$ and $F$ are the displacement and force vectors.
How can one determine the ...
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83
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Kinetic energy conservation in different reference frame
Let us assume that there is a bowl fixed on a table. The radius is R. There is a small ball on the top such that it has a potential energy of $mgR$. When the ball is dropped, at its lowest point it ...
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