New answers tagged potential-energy
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Minimizing the action - particle in a potential well
About change of motion:
When an object is in a situation where there is a gradient in the potential then the object will accelerate down the potential gradient.
Given that acceleration: the stationary ...
- 22.2k
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Accepted
Minimizing the action - particle in a potential well
The principle of least action is poorly named, because often the classical solution corresponds to a saddle point, and not actually a minimum of the action. The condition that you use to derive the ...
- 52.3k
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Why does acceleration seem not to be the gradient of gravitational potential?
In fact, this seems to be a universal and a very logical rule since potential is like energy concentration- masses are accelerated by the negative of the gradient of energy too. To move something of ...
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Accepted
A man standing in an elevator at the third floor of a building. What is the primary factor that determines the man's kinetic energy?
First of all, kinetic energy (KE) is reference frame dependent. In the frame of the elevator, as long as the man moves with the elevator, the man's KE will always be zero.
That said, in any other ...
- 75.7k
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A man standing in an elevator at the third floor of a building. What is the primary factor that determines the man's kinetic energy?
The question is a bit misleading so let's go straight to it.
If the elevator's speed is $v = 0$, then the mass has no effect whatsoever and $v$ is the "primary factor" causing $K_E = 0$
If ...
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Gravitational potential energy of a water column
The velocity decreases as the column height falls
The total energy contained in the column is $mgh \over 2$. So, if we pull the plug and let the column drain out, then the total kinetic energy must be ...
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Gravitational potential energy of a water column
Lets consider a cylinder full of water that is 100 metres high with a cross sectional area of 2 $m^2$ so the volume of water is $200 m^3$ and the mass is 200 tonnes. The initial potential energy of ...
- 7,606
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Gravitational potential energy of a water column
If the column of liquid has density $\rho$, cross-sectional area $A$ and height $h$ then its mass is $m = \rho A h$ and its PE is
$\displaystyle PE = \frac {mgh} 2 = \rho A g \left( \frac {h^2} 2 \...
- 57.6k
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Gravitational potential energy of a water column
You are correct that if you are considering the GPE of the whole column, then you should take $\frac h2$ because that is the average height of the water.
But when considering the water that is coming ...
- 10.2k
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Why is charge on a conductor stable?
Yes that's right, for a charged conductor the electric field outside the surface is directed such as to pull charge off the surface. The reason the charge doesn't leave the surface is to do with what ...
- 60.2k
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How potential energy is created in Electric dipole?
I understood the things that missing in the concept of potential energy from answers. The thing is represented in the fig. below. Whenever the dipole is placed in the Electric field, it experiences a ...
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How potential energy is created in Electric dipole?
Probably, the missing information is that, similarly to the case of a force's work, there is also work in the presence of an angular displacement in the presence of a torque (see, for instance, this ...
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How potential energy is created in Electric dipole?
So, in case of dipole, how does it acquire potential energy without
any work done?
An external agent needs to do work to rotate the dipole to be perpendicular to the field in order to acquire ...
- 75.7k
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Equilibrium position of a body attached to a spring
The equation $x=mg/k$ gives the position where the mass has attained equilibrium. At this point, the body has attained equilibrium but it isn't necessarily true that the body is at rest. The body ...
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Why do we reduce a body to its center of mass when calculating gain/loss of gravitational potential energy?
A real object in a gravitational field has some potential energy (we assume the gravitational field to be uniform over the relatively small size of the object). Now take a point object with zero size ...
- 10.1k
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Why do we reduce a body to its center of mass when calculating gain/loss of gravitational potential energy?
KDP's answer explains, in elementary terms, why this reduction is acceptable for a uniform rod in a uniform field. This is an elaboration of that answer in case you prefer a more formal derivation.
If ...
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Hanging mass from spring/ Setting potential to 0
What I am not clear on is what we are actually doing mathematically
when we "set U=0".
To find the potential energies we are integrating the displacements from a chosen origin. When we ...
- 7,606
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Why do we reduce a body to its center of mass when calculating gain/loss of gravitational potential energy?
Consider a mass at height h above the surface and another mass at height (h+L) that are connected by a massless rod. The potential energy of the lower mass is -mgh and the potential energy of the ...
- 7,606
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Why do we reduce a body to its center of mass when calculating gain/loss of gravitational potential energy?
When resolving KE of a rigid body the choice of reference point where velocity is calculated and the mass moment of inertia is resolved about are arbitrary.
Specifically, a rod of length $\ell$ that ...
- 38.9k
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Violation of work-energy theorem (WET) in deriving potential energy (PE) of current-carrying ring in a uniform magnetic field
I am not much of an expert in electromagnetism but the entire reason behind my answer is that you got the WET wrong. I know that many textbooks do not write it properly, so it's not your fault.
The ...
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Violation of work-energy theorem (WET) in deriving potential energy (PE) of current-carrying ring in a uniform magnetic field
Is it not violation of work-energy theorem (WET) as Work done by
external agent is the change in Kinetic Energy and not change in
potential energy (PE)?
In the work energy theorem the work is net ...
- 75.7k
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Relation of field of force to potential energy
According to the multivariable chain rule the total differential of a multivariate function, for example $f(x,y)$, is:
$$\mathrm df = \frac{\partial f}{\partial x}\mathrm dx + \frac{\partial f}{\...
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Accepted
Understanding the concept of work and potential energy
Two points:
Because of the definition $$\tag1 \text {work}=\Delta \text{potential energy} =\bf F\cdot x$$ where $\bf F$ is the force ($\bf x$ is displacement), the work done would be zero. The ...
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How does gravitational potential energy work in a very large distance?
Initially, they are millions of light-years apart, with the asteroid
slowly moving away from the planet at a velocity exceeding the escape
velocity at that distance (1 cm/century).
Conventionally, ...
- 7,606
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Gravitational potential at any point
When you did the integration (first line in the text box), you've used the limits $0$ to $\infty$. In the "standard" derivation, you integrate from $\infty$ to $0$, because the potential at ...
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