Finding the potential energy if force depends on both position and time

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Discussion Overview

The discussion revolves around determining the potential energy associated with a force that depends on both the position of a particle and time. The specific force under consideration is given by f(r,t) = (k/r^2) * exp(-alpha*t), where k and alpha are positive constants, r is the position from the force center, and t is time. The scope includes theoretical implications of conservative versus non-conservative forces and the utility of potential energy in such contexts.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether the given force is conservative or non-conservative, noting the dependence on both position and time.
  • Another participant suggests that a time-varying potential is generally not considered conservative but mentions that if the time scale of motion is small compared to the rate of change of the potential, it might be treated as a pseudo potential.
  • A different participant emphasizes that the usefulness of the concept of potential energy is questionable in this scenario, as energy conservation may not apply over time.
  • Another participant states that with a highly time-dependent force, the concept of energy may not be well-defined or useful.

Areas of Agreement / Disagreement

Participants express differing views on the classification of the force as conservative or non-conservative, and there is no consensus on the utility of potential energy in this context. The discussion remains unresolved regarding the applicability of energy concepts.

Contextual Notes

Participants note limitations regarding the definition and utility of potential energy in the presence of time-dependent forces, as well as the implications for energy conservation.

swapnilp
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How to find potential energy if force depends on both position of particle and time ?

Suppose force is : f(r,t) = (k/r^2) * exp(-alpha*t),
k, alpha = positive constants,
r = position of the particle from force-centre
t = time

Is this force a conservative or non-conservative ?
 
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A time varying potential is generally not considered conservative. However, if the time scale of the interesting motion is small compared to the rate the potential is changing, you can call this a pseudo potential. Over a short time scale the energy will approximately only depend only on position.
 
swapnilp said:
Is this force a conservative or non-conservative ?
The question is rather how useful the concept of a potential is here. You don't have the usual energy conservation over time. Depending on what you want to compute, using the force itself might be simpler.
 
Last edited:
With a highly time dependent force like the one you have there the concept of energy is not exactly defined or useful.
 

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