Find the Time period using First Integral

In summary, the conversation discusses a problem involving finding the time period of a particle confined to a potential energy function. The person asking the question attempted a solution, but was unsure if it was correct. It was determined that in order for the motion to be periodic, the total energy of the particle must be less than zero. The person asking the question was unsure if their solution was correct.
  • #1
Muthumanimaran
81
2
Recently I lend the Classical mechanics book written by Goldstein from the library, In the last page, someone scribbled this problem without any solution, I am just curious and want to give a try the problem mentioned below. I just want to know whether my approach and my solution is correct or not.
1. Homework Statement

Find the Time period of the particle confined to the Potential energy of the form $V(x)=-\frac{V_{0}}{\cosh^2(\alpha{x})}$.

Homework Equations


$$\int_{0}^{t_0}dt=\int_{x_0}^{x}\frac{dx}{\sqrt{\frac{2}{m}(E-V(x))}}$$
Where $'E'$ is the Total Energy
and $'m'$ is the mass of the particle

The Attempt at a Solution


Since the potential energy is negative, the total Energy required to escape from the potential is zero, i.e, $E=0$,
The Potential diagram is attached with this thread, as we can see, the potential goes to 0 as $x$ goes to $\infty$
or $-\infty$, If I take one half of the Potential say from $0$ to $\infty$ and substituting in the above integral becomes,

$$\int_{0}^{\frac{T}{2}}dt=\sqrt{\frac{m}{2V_0}}\int_{0}^{\infty}cosh(\alpha{x})dx$$

Apparently the right hand side goes to infinity. And the time period of the particle confined also goes to infinity. Am I right? I solved the problem but I don't know whether my solution is correct or not. Is there any mistake in my solution?
 

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  • #2
If you take E = 0 there is no classical turning point and the motion is not periodic. In order to have a periodic solution you need to assume a bound state with E < 0.
 

1. What is a first integral in relation to finding the time period?

A first integral is a mathematical concept used in the study of dynamical systems. It is a function that remains constant throughout the motion of a system, and can be used to determine the time period of the system's motion.

2. How is a first integral used to find the time period?

By setting the first integral equal to a constant and solving for time, we can determine the time period of the system's motion. This method is particularly useful for systems where the equations of motion are difficult to solve directly.

3. What types of systems can be analyzed using first integrals?

First integrals can be used to analyze a wide range of dynamical systems, including mechanical, electrical, and biological systems. They are also applicable to systems with multiple degrees of freedom.

4. Are there any limitations to using first integrals to find the time period?

While first integrals can be a powerful tool for determining the time period of a system's motion, they are not applicable to all systems. In particular, they cannot be used for systems with non-conservative forces or systems with chaotic behavior.

5. How is the time period affected by changes in the system parameters?

The time period of a system can be affected by changes in the system's parameters, such as mass, length, or stiffness. By manipulating the first integral equation, we can see how these changes impact the time period and make predictions about the system's behavior.

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