# 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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### Why does Alan Guth state that "Newtonian physics unambiguously implies that the energy of a gravitational field is always negative"?

Quoting him from: Published in "The Beamline" 27, 14 (1997) "Although it has not been widely appreciated, Newtonian physics unambiguously implies that the energy of a gravitational ...
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### Can the applied force be greater than electric force? Why is the applied force considered to be equal to electric force?

If the applied force is greater than that of electric force, will the work done by applied force formula still hold? Why is the potential energy negative of work done by electric force? Why can't it ...
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### How can we still use the potential, when there is applied force, as it might also contribute to the change in potential energy? [closed]

If the applied force and the electric force are everywhere equal, will the applied force considered as conservative, although it changes the total energy of the system?
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### Conservation of energy in a mechanical system with a discontinuous potential function

I've started reading Landau-Lifshitz Mechanics, and I'm having trouble with the problem at the end of section 7. A particle of mass $m$ moving with velocity $\mathbf{v}_1$ leaves a half-space in ...
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1 vote
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### Defining potential energy [closed]

Let's say we are talking about gravitational potential energy, it is defined as: At a point $X$, inside the gravitational field of mass $M$, the work done by an external agent to bring a mass $m$ ...
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### Significance of negative work done

Suppose, I am lifting a ball of mass $m$ very slowly from the ground to a height $h$. That is,for the whole time,approximately, $F_{me}=-F_g$ I am doing a work of $+mgh$, which is transferred to the ...
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### Type of collision of two billiard balls

My textbook has the following question: If the potential energy of two billiard balls depends only on the seperation distance between their centres, is the collison elastic or inelastic? (Note: we ...
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### Can't one always define $U=-m\ddot xx$?

Can't one always define $U=-m\ddot xx$ so that $$F=m\ddot x=-\frac{\partial U}{\partial x}?$$ An example is gravitational potential energy $U=mgh$ where $h=x$ and $g=-\ddot x$. I know this has to be ...
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### Is it possible to charge a zero potential ball?

I've been studying electrostatic potential and capacitance and am curious about the Earth's role in absorbing charge. The Earth is often considered an almost neutral body that can absorb an unlimited ...
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### Good question on spring potential energy [closed]

A Spring of constant 100 Newton per metre is stretched by applying equal forces each of magnitude F at the two ends the energy stored in the spring is 200 Joules .Now the spring is cut into two equal ...
1 vote
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### How can you have a potential in a theory without any forces?

Consider the typical Lagrangian: $$L=\frac{1}{2}(\partial_\mu\phi)(\partial^\mu\phi) - V(\phi).$$ I interpret the above (please correct me) as a theory consisting of a field which can move through ...
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### Why can generalized forces be derived from generalized potentials? Doesn't this confuse their relation to kinetic energy?

In Wolfgang Nolting's 'Analytical Mechanics', the concept of 'generalized potential' is discussed: For non-conservative systems, but with holonomic constraints, instead of that, the starting point ...
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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 ...
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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 ...
1 vote
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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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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 ...
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. ...