# Tagged Questions

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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### Work to assemble charge distributions in the presence of a dielectric

I am asked by a problem to: Find the potential energy of a point charge in vacuum a distance $x$ away from a semi-infinite dielectric medium whose dielectric constant is $K$. I wish to approach ...
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### When water turns to steam at 100 degrees Celsius why does both the internal and potential energy increase?

I thought during this transition only the potential energy increases as energy is used to weaken the van Der Waal forces between the molecules. And that the internal energy is only dependent on the ...
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### What is rotational potential energy?

I don't understand the concept of rotational potential energy. During linear motion, when a force is applied, the work it does gets converted to kinetic energy and there is no change in the ...
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### Loop the loop question: A marble of mass $m$ and radius $r$ rolls along the looped track in the image [on hold]

A marble of mass m and radius r rolls along the looped track in the image: What is the minimum value of H if the marble is to reach the highest point of the loop without leaving the track?
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### Why does positive work done by internal conservative forces $\implies$ decrease of potential energy?

Potential energy can be thought as the amount of work that the force can potentially do on the point because of its position. $$W=-\Delta U=U_{initial}-U_{final}$$ A positive work done by a force ...
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### Charging by induction

When we charge an conductor by induction and grounding, we first bring a negative charge to the conductor. As a result the mobile electrons of the conductor get repelled and stay far from the negative ...
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### Oscillation of a simple pendulum [on hold]

What is maximum possible time period of oscillation of a simple pendulum on earth? Please elaborate your answers.
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### Work done by an ideal gas expressed as change in potential energy of fluid

I get confused in problems where it is necessary to evaluate the work done by a gas that someway moves a mass. I'll make an example. Consider the tube containing mercury and an ideal gas in A (...
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### Forces from molecular potential energy surface

Let's assume we cannot use Hellmann-Feyman theorem and we wish to calculate the forces on molecules' atoms at arbitrary configuration only from its potential energy. My question is how many different ...
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### Energy Stored in Spring [on hold]

Area Z represents the energy stored in the spring when it is stretched to a length L I am trying to understand why this is so: $$E = \frac{1}{2}kx^2$$ Here, $x$ is the vertical side of triangle $Y$...
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### Confusion in the derivation of the potential of a magnetic shell

I am reading an old book on electromagnetism (THE MATHEMATICAL THEORY OF ELECTRICITY AND MAGNETISM) and I have some confusion in the following pages: First let me clarify what a "magnetic shell" ...
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### Why a positive voltage raises the potential energy of a positive charge and lowers the energy of a negative charge?

I am reading the relation between energy diagram and V, E (electric filed) in a semiconductor from the site (page 47-48). However, I don't quite understand this sentence below. Could anyone explain ...
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### Center of mass error - calculating systematic error in change in PE

Suppose we have to calculate systematic error in change in PE. Let's suppose systematic error due to scale is 1%. I'm confused about the center of mass error. \begin{align} \Delta PE = m*g*h_1 - m*g*...
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### Is the Potential Energy just a bookkeeping device?

It is said that if the space is homogeneous then momentum is conserved. But I've been thinking in the following situation: Consider a parallel plates capacitor. In between the plates there is a ...
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### Can the momentum of a system be spacelike?

For a particle, we always have $Eu=p$ where $u$ is the speed of the particle and correspondingly the momentum is always timelike. For a system of particles, if the potential energy is not considered ...
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### Relation between gravitational field and gravitational potential

The gravitational field is the negative differential of the gravitational potential. Now the gravitational potential due to a particle at a distance $r$ is $-Gm/r$ where $m$ is the mass of the ...
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### There is a system of 2 electrons approaching each other.Want to know how the system gained the potential energy? [closed]

Well there is a system of 2 electrons approaching each other with a velocity 'u'. The question here is to find the closest distance of approach, r after which they start moving in opposite directions. ...
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### Relation between field and Potential energy of a body

I have read that if a body is in a field and is 1. moved in a direction opposite to the direction of a field, its potential energy increases.But why does it increase? 2.Also, if we move the body in a ...
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### Is this thought regarding work and potential energy correct?

I am really confused about this. The potential energy acquired by an object is equal to $mgh$, if we are on any planet, where $g$ is the planet's gravitational acceleration, which directly comes from ...
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### Help understanding the solution to a problem regarding kinetic energy of a group of point charges

The problem provided by my professor goes as follows: "Now consider a situation in which all charges are equal to q and they simultaneously become "unglued". What speed will each charge have when a ...
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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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### Problem with derivation of potential enery of two body in Gravitational energy

Maybe what I'm going to ask sounds stupid but it means a lot to me that's why I'm asking. I've problem with just a single step in derivation. Let's start. I'm keeping in mind the direction of each ...
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### Does the mass of a brick increase when you lift it? [duplicate]

If a person takes a brick, and lifts it to a height of 1 m, will the mass of the brick increase?
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### Electrostatic energy of the system

Problem : $(A)$ There are two thin concentric metallic shells of radius $a$ and $b$ $(b>a)$. Inner shell carries a total charge $Q$ and the outer shell carried a total charge $–Q$. Calculate the ...
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### Centrifugal force in the two body problem?

In the two body problem, the Effective radial potential energy in general relativity is given by $$V(r)=-\frac{G M m}{r}+\frac{L^{2}}{2\mu r^{2}}-\frac{G(M+m)L^{2}}{c^{2}\mu r^{3}}$$ where the ...
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### Need help with signs (+ -) in electric potential work and potential energy problem

The problem is from Sears and Zemansky's University Physics, 12th edition in Spanish. The problem says: How much work is needed to assemble an atomic nucleus that contains three protons if it is ...
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### Is an extended spring gain mass from potential energy? [duplicate]

Is it true that when a spring is extended, potential energy is stored in spring and result in gain of mass of the spring?
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### Potential energy

In what form is potential energy stored in a system? I understand that when we do work we transfer some amount of energy to the system it can be seen as kinetic energy or potential energy. Suppose we ...
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### How can energy be negative in a finite square well?

Say if the potential $V(x) < 0$ in the well but the sides or the scattered states its zero potential, anyways How is that the energy in the well is less than zero? Is it because the potential ...
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### Final potential difference between plates of capacitor [closed]

If the plates of a parallel plate capacitor are given charges 4Q and -2Q . The capacitor is then connected across an uncharged capacitor of the same capacitance as first one (=C) . Now we have to find ...
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### As distance increase why no change in electric field in parallel plate condenser [duplicate]

If the distance between the plates of a parallel condensor is 4mm and the potential difference is 60 volts. Now if we increase the distance between the plates to 12mm, then: Why the electric field ...
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### Potential Energy for dipole in Electric Field

Potential Energy is the work done by the external agent in turning the angle of the dipole from the U=0 position to another position against the influence of the electric field applied right? So if ...
259 views

### Potential energy of springs and gravity, and work of a force

I am currently really stuck on this problem and I am not sure how to actually solve it, I think I can reason it out logically but I do not know how to show it. Here it is and under I will show what I ...
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### Interaction Potential for Damped Driven Pendulum

I'm trying to use the velocity Verlet integrator to simulate a damped driven pendulum (with unit mass) described by $\ddot{\phi}+\gamma \dot{\phi}+\omega_0^2 sin\phi=Acos(\Omega t)$ The Verlet ...
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### How to Explain the the following situation?

I have thought a simple thing: consider a system of a planet and its natural satellite revolving around it in a perfectly circular orbit(assumed) and this is happening in an isolated space in some ...
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### Springs, elastic potential energy, kinetic energy

If a ball with some kinetic energy collides with a spring, the ball doesn't lose its kinetic energy in an instant, right? it loses kinetic energy as the spring gains potential elastic energy. Right? ...
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### How is gravitational time dilation different from time dilation due to differences in speed? [duplicate]

This is what I understand from what I've been reading online: In the derivation for the gravitational time dilation equation, $$t = t_0\sqrt{1-\frac{2GM}{rc^2}}$$ we use the special relativity ...
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### Do the energies of cosmic rays approach infinite at the event horizon of a black hole?

Let's assume an observer orbits close to a black hole, he is not alone, massive cosmic rays, like electrons and protons and other kind of space dust comes from the outer space and may hit him. Since ...
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### Force and energy relation: in case of time dependent force

The equivalent problems are also found in Marion problem 7-22, and other formal classical mechanics textbook. Here what i want to know why instructor solution and some websites gives this kinds of ...
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### Center of mass problem

According to the definition of potential energy, we use $U= mhg .$ In the figure below , A thin uniform rod of mass m and length h is positioned vertically above an anchored frictionless pivot ...
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### Why do molecules in a gas not generally arrange themselves at the distance of minimum potential energy (Lennard-Jones 6-12 potential)

As the title suggests, why is this? Is it because the distance of molecules in a gas is too large (compared to in liquids/solids)? Or are there other reasons for this?
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### Schrödinger equation for many body systems

$$H_{tot}=\sum \dfrac{p_i^2}{2m}+\sum\dfrac{p_I^2}{2M_I}+\sum V_{nucl}(r_i)+\dfrac{1}{2}\sum_{i\ne j} \dfrac{e^2}{|r_i-r_j|}+\dfrac{1}{2}\sum_{I\ne J}\dfrac{z_Iz_Je^2}{|R_I-R_J|}$$ with: V_{nuc}...
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### Basic Classification of Energy [closed]

When I was still in school, I learnt that there are 2 types of energy: Potential & Kinetic Energy. When I searched Wikipedia and other sources, there were many forms of energy. There are some ...
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### Is it possible to determine how many electrons there are in a plate from its voltage?

We've just stared doing voltage in school, and so I wondered if this is possible :) If I charge an insulated metal plate using an EHT to something like 5kV, then I've added electrons to the plate. My ...
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### Why did Trebuchet have so long throwing arms?

Have a look at such an historical Trebuchet: As you can see, the throwing arm (left) is much longer than the weight arm (right). Law of conservation of energy says, potential energy from the ...
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### Electrostatics, System of Charges [closed]

At $t=0$, a positive point charge of mass $m$ is projected toward another positive point charge of mass $m$ in free space. At the instant of minimum separation kinetic energy of the system of two ...
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### How to prove that the potential of a conservative central force depends only on the magnitude of the distance & not on the direction of the vector?

If a conservative central force acts on a body then its potential only depends on the magnitude of the distance between two bodies (does not depend on direction of vector). Is there any proof of it ...
A satellite of mass $m$ is travelling at a speed $v_0$ in a circular orbit of radius $r_0$ around a fixed mass at $O$. Taking the zero of potential at $r=\infty$, show that the total energy of the ...