How Do You Determine U(x) for a Particle Under a Nonlinear Force?

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In summary, the conversation discusses a one-dimensional problem where a particle is under the influence of a force described by F=-kx+kx^3/(a^2), with k and a as constants and k being positive. The main objectives are to determine U(x) and to discuss the motion of the particle. The conversation also mentions finding U(x) using the fact that F = -dU/dx in one dimension. Additionally, the question of what happens when E=1/4 (k a^2) is brought up.
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eku_girl83
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A particle is under the influece of a force F=-kx+kx^3/(a^2), where k and a are constants and k is positive. Determine U(x) and discuss the motion. What happens when E=1/4 (k a^2)?

I know F = - grad U, but how do I use this fact to set up the problem?
Can someone help me to get started?

Thanks!
 
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  • #2
This is a one-dimensional problem, so no need for gradients. Just F=-dU/dx

So start by finding (a) U(x).
 
  • #3
eku_girl83 said:
A particle is under the influece of a force F=-kx+kx^3/(a^2), where k and a are constants and k is positive. Determine U(x) and discuss the motion. What happens when E=1/4 (k a^2)?
I know F = - grad U
In one-dimension, that's F(x) = -dU(x)/dx. Now what can you do to express U(x) in terms of F(x) ?

Edit : Started before Galileo's post was up...now redundant as it's saying the same thing.
 

1. How can I determine the potential energy function (U(x)) from a given force function?

The potential energy function (U(x)) can be determined by integrating the negative of the force function with respect to the position (x). This is based on the relation F = -dU/dx, where F is the force and U(x) is the potential energy function.

2. Is it always possible to determine the potential energy function from a given force function?

In most cases, yes. However, there are certain force functions that may not have a corresponding potential energy function. This is due to the fact that the potential energy function must be continuous and have a single value at each point in space.

3. Are there any assumptions or limitations when determining the potential energy function from force?

Yes, there are a few assumptions and limitations. First, the force function must be conservative, meaning that the work done by the force in a closed path is zero. Additionally, the potential energy function may not be unique, as adding a constant value to it will not change the force function.

4. Can the potential energy function be determined experimentally?

Yes, the potential energy function can be determined experimentally by measuring the forces at different positions and then using numerical methods to integrate and obtain the potential energy function.

5. How does the potential energy function relate to the stability of a system?

The potential energy function is related to the stability of a system through its critical points. The critical points of the potential energy function correspond to the equilibrium points of the system, where the forces are balanced. The type of critical point (maximum, minimum, or saddle) determines the stability of the system.

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