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.
-4
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2answers
55 views
Is time/gravity the source of all energy? [on hold]
I have always been confused about the concept of potential energy. If you raise an object $X$ meters above the ground, it gains $Y$ energy. Simple enough, however, what happens when you keep moving ...
1
vote
1answer
27 views
Problem regarding finding work done
This problem is given in my physics book. How much work will be done if anyone wants to stack up 12 bricks? Given that each brick is $10 cm$ high and each brick's mass is $2 kg$. ($g=9.8$)
Now in ...
0
votes
1answer
51 views
How to find potential energy of ball attached to two springs with mass $m$? [on hold]
the questions states the following:
A ball is attached to two springs in the middle, spring $A$ has a spring constant of $k_A$, spring $B$ has a spring constant of $k_B$. The ball has a mass of $m$...
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votes
0answers
58 views
Newton's 2nd Law [closed]
I know that Newton's 2nd law of motion if $$F = ma.$$
But i saw an equation that the law is stated as:
$$m * (d^2x/dt^2) = - dV/dx.$$
I understand the first part of the equation, but i don't ...
-1
votes
1answer
63 views
Notation in One-dimensional Schrodinger equation
I am reading a book where it write the one-dimensional stationary Schrodinger equation as
$$
[-\frac{\hbar^2}{2m}\frac{d^2}{dζ^2}-Γ{\rm sech}^2(bζ)]ψ(ζ)=Eψ(ζ).
$$
It is known that the equation is ...
0
votes
1answer
44 views
Why is potential energy zero in this calculation of partition function?
In section 7.2 of Rief's "Fundamentals of Statistical and Thermal physics". While calculating the partition function for ideal gas he writes:
$$
\begin{array}{l}
\displaystyle{Z'
= \int{
\...
3
votes
0answers
127 views
How much water can an object raise after its fall? [duplicate]
Suppose that there is a small object (e.g. hand sized) with volume $V$ and mass $m$ that falls into a water container from a height $h_0$ and with initial velocity $v_0$. Is there a way to compute the ...
-1
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3answers
70 views
Can someone explain this equation more clearly: $\Delta E_{Total}=\Delta K + \Delta U = W_{External}$
I asked my Physics teacher and he explained it to me, but I am still confused on how to use it.
\begin{equation}
\Delta E_{Total}=\Delta K + \Delta U = W_{External}
\end{equation}
I think it's the "...
3
votes
1answer
49 views
How does a rolled piece of paper lose its Elastic Potential Energy
If you roll up a piece of paper and leave it for years it will stay rolled up. If you leave it rolled up for a minute it is easy to unroll. Of course this must be because the energy stored in that ...
3
votes
1answer
47 views
What is the relationship between velocity-dependent potentials and non-Abelian gauge fields?
My (limited) understanding of non-Abelian gauge fields is that they arise from the construction of a theory using a non-Abelian Lie group (as a generalization of the Abelian group underlying E&M) ...
0
votes
2answers
79 views
Generalized force arising from a velocity-dependent potential
On slide 16 of this presentation it is stated without proof that given a velocity-dependent potential $U(q,\dot q, t)$, the associated generalized force is $$Q_j = - \frac{\partial U}{\partial q^j} + \...
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votes
1answer
78 views
Motion of an electron near a proton [closed]
Statement of the problem:
Consider an electron and a proton that are initially at rest separated $a$ meters. Do not take into account the movement of the proton, because its mass is much greater ...
0
votes
1answer
51 views
Change in electric potential energy after sphere splits in two
The problem:
Consider a uniformly charged sphere of radius $R$ and charge $Q$ and then they separate into two spherical halves of equal volume and charge, and both get to stabilize. Determine the ...
0
votes
1answer
53 views
Relation between central force and potential energy
I read this in one of the comments at this site
"Any force that admit a potential is conservative"- what does it mean? Because I want to know why central force is related with potential as I have ...
0
votes
1answer
42 views
Is it possible that the particles can be brought by some external agency without changing the kinetic energy? [duplicate]
I am a student and I've been studying a physics book. There is one statement in the solution of one question (regarding calculation of Potential energy) which is confusing me. It states that:
If ...
0
votes
0answers
37 views
Orbits in the effective potential $U(r)=k(r^2 -a^2)e^{-br^2}$
Given the effective potential $U(r)=k(r^2 -a^2)e^{-br^2}$, where $r$ is the spherical radial coordinate, could a particle oscillate near $r=0$ even when the particle cannot go to a coordinate with ...
-2
votes
1answer
31 views
What is the largest radius that the circular track can have such that the car remains in contact with the track? [closed]
A car is travelling at $u$ as it enters a vertical loop of radius $r$.
What is the largest value of $r$ that the track can have such that the car goes up and around the track whilst remaining in ...
1
vote
1answer
38 views
Electron gas and the infinite potential well
I want to fully understand the electron gas but I am sometimes confused about its behaviour, due tho its models.
So the materials like metals got its ionts periodically arranged in the crystal ...
2
votes
2answers
115 views
Susskind & Hrabovsky: For any system $F_i=-\partial_{i}V$?
In the following $\left\{x\right\}$ means a configuration point in $3N\text{-dimensional}$ configuration space. Each $x_i$ represents one coordinate of one particle of the system of $N$ particles.
...
0
votes
0answers
18 views
Principle of least action for dissipative systems [duplicate]
I am trying to solve a problem with involves friction, and am having trouble solving it with $F=ma$. I am considering to use Lagrangian mechanics, but I am puzzled. There doesn't seem to be a ...
0
votes
0answers
26 views
How understand the stored energy due to magnetic field? [duplicate]
I'm confusing because in this book1 introduces the magnetic energy as mechanical work done by forced magnetic, but if magnetic force doesn't work, besides do who done work?
Teruo Matsushita - ...
0
votes
3answers
60 views
When talking about potential difference in a circuit, whose work done are we talking about?
I'm asking this because it seems to me that when we talk about PD around a charge (i.e. potential difference between infinity and a point), we're talking about the work done per unit charge by an ...
2
votes
2answers
54 views
Confusion about Electric potential
From what I understand the electric potential at a point $P$ is the amount of work done per unit charge $q$ in bringing that charge $q$ to the point $P$. Now consider the following question: The ...
1
vote
2answers
50 views
Conservation of mechanical energy when a ball is released from a height
An isolated system means that no energy should be transferred or taken away from it. Let us consider a ball- earth system. Mostly the law of conservation energy is proved when the ball is released ...
0
votes
2answers
35 views
Derivation of the formula for Electric Potential Energy
I just learnt the formula for calculating Electric Potential Energy
$W=\frac{1}{C}\int_0^Qqdq = \frac{1}{C}[\frac{1}{2}q^2]_0^Q=\frac{Q^2}{2C}$
I understand the methodology, but what I do not ...
1
vote
1answer
82 views
How do we know relativistic mass also includes potential energy?
From Special Relativity it is shown that relativistic mass increases with kinetic energy, but how do we know potential energy is also part of relativistic mass? Is this a derived conclusion, or should ...
1
vote
1answer
48 views
Question regarding electrostatic potential energy [duplicate]
I was calculating potential energy due to point charge at origin using relationship
$$U=\dfrac{1}{2}\epsilon_{0}\displaystyle\int \mathbf {\vec E.\vec E\ } \ d\tau$$
and it comes out to be ...
0
votes
1answer
58 views
Potential potential?
I'm a noob trying to understand concepts before details (which itself could be a mistake cuz I think my head is about to explode)
A big part of my difficulty is terms - they are blocking my conceptual ...
0
votes
3answers
39 views
Why is the gravitational potential energy (or electrical) the work done to move a point mass $m$ from infinity to that point in a gravitational field?
To be specific, I'm asking why does the mass need to be moved "at a constant speed"?
My textbook says it is so that no kinetic energy is involved. But shouldn't kinetic energy be involved in order ...
6
votes
2answers
341 views
What is the physical reason for why gravitational potential (or electrical potential) due to two masses at a point can simply be added algebraically?
The simple explanation that textbooks and the internet say is that "gravitional potential is a scalar quantity hence can be added algebraically".
However, I'm not sure if it is that simple. Take for ...
0
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0answers
30 views
Question about Work performed between two points within an electric field
In an exercise in my Physics Textbook, I was asked to calculate the amount of Work necessary to move a charge of -$1.6\cdot10^{-6}$ Coulomb from P to R, and from R to O (see attached picture below).
...
4
votes
3answers
225 views
Electric Potential Energy of a charged conductor
My physics textbook asks (I translate):
A sphere of copper with a radius of 0.72 metres is charged with a Potential of 270,000 Volt. Find its charge and the electric energy it holds.
I found the ...
0
votes
1answer
42 views
Decreasing energy but at expanse of what
question : A hollow spherical shell with radius R has charge Q uniformly distributed
over it.
(i) show that the energy
stored in this system is $\dfrac{Q^2}{8\pi \epsilon_{0}R}.$
(ii) Now imagine ...
0
votes
1answer
47 views
The meaning of the time derivative of potential energy
Here's the link: http://www.feynmanlectures.caltech.edu/I_13.html
\begin{equation}
\label{Eq:I:13:16}
\frac{d}{dt}\sum_i\biggl(\sum_j-\frac{Gm_im_j\mathbf r_{ij}}{r_{ij}^3}\biggr)\cdot \mathbf v_i=
\...
0
votes
0answers
123 views
Bragg reflection causes energy gaps between energy bands - Why?
I know that Bragg reflection in solid states at the edge of e.g. the first Brillouin Zone causes standing waves at these edges, which creates a gap between the energy bands.
In this picture you can ...
0
votes
1answer
32 views
feynman shell theorem
I understand the general derivation of the shell theorem by feynman but I don't get why he denotes the potential energy with W, the symbol for work. I would understand this if they would be the same ...
0
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3answers
30 views
Potential energy and work-energy theorem
Let us suppose that a ball is present on earth's surface, gravity acts on it. Now if a force is applied on the ball in the opposite direction of gravity such that the applied force counters gravity ...
1
vote
3answers
171 views
Is gravitational energy always conserved?
If I take a body to a height $h$ then I did the work $mgh$, but gravity does the work of $-mgh$, so the net work done would be 0. So why do we say that at that height $h$ the body will have potential ...
0
votes
3answers
48 views
Energy of a planet moving around the Sun
In chapter 13 of volume 1 of The Feynman Lectures, Feynman is discussing how the work done in going around any path in a gravitational field is zero. Here's the link: http://www.feynmanlectures....
4
votes
1answer
87 views
Does the negative sign in the Lagrangian $L=T-V$ relate to the $(+,-,-,-)$ Minkowski signature of relativity?
I've read many derivations of the Euler-Lagrange equation, but this is more of a physics-philosophical point.
Kinetic energy $T$ involves time derivatives, while potential involves spatial location. ...
3
votes
2answers
36 views
Energy and Speed of Electrons in a Circuit
I really wonder about the relationship between potential and kinetic energy in a circuit. At the positive terminal of the battery, there will be high potential energy. The difference in electric ...
10
votes
0answers
302 views
Explicitly verifying a scattering theory identity
I have recently studied scattering theory on a formal level and I think I understand the subject quite well by now. However what I often struggle with is to translate the abstract identities into ...
0
votes
0answers
25 views
Breaking spaghetti and conservation of energy [duplicate]
For the past few days there have been news about scientists solving the old problem of bending a piece of spaghetti and breaking it into exactly two halves. Earlier it was already determined that the ...
0
votes
3answers
108 views
Kinetic energy and conservative fields
If $W = E_1 - E_0$ for every force and a conservative field is a field such that the work on a closed path is 0, then every field should be conservative, since $W = E_0 - E_0 = 0$.
I know that this ...
2
votes
0answers
38 views
Potential gravitational energy versus potential spring energy [duplicate]
My textbook points out the following predicament, and I do not know the answer, despite a lot of thinking:
A spring is hanging of a ceiling and a mass is attached. As a result the spring descends to ...
2
votes
2answers
34 views
Calculating Elastic Potential Energy of a Stretched Sheet
Essentially, I'm trying to determine the amount of elastic potential energy stored in a thin, elastic sheet that has gone under some type of stretching (ex. A flag of stretchy fabric waving in the ...
0
votes
1answer
24 views
Lost potential energy?
If there are two electrons and a positron are in an closed system (not being influenced by gravity) all these have electromagnetic potential energy amongst them . if one of the electron then touches ...
53
votes
15answers
12k views
When a balloon pops and lets a brick fall, where does the energy come from?
Let's say a scientist attaches a 1 kg brick to a large helium inflated balloon, lets the balloon go, and then it reaches an altitude of 10 000 meters before it pops, dropping the brick.
The brick ...
-2
votes
2answers
53 views
Is it possible to avoid a dangerous collision with the ground after free fall by converting the potential energy into rotational kinetic energy?
Is a human body able to survive if someone sabotages your parachute and you're in a free fall towards earth suddenly realizing that you have one out of two options left- either die or stand on the ...
-6
votes
3answers
114 views
Is this a new form of renewable energy? (sand) [closed]
Can we make a machine that takes a mass of sand from the top of a sand dune keeps it in a box.
Then moves it horizontally until it is hovering above the lowest point near the slipface of the dune.
...
