Differential equations - transforming from one to another

In summary, the conversation discusses two differential equations for different physical phenomena. The first equation represents the movement of a mass along an x axis, with a springforce, dampener, and outer force. The second equation is mathematically equivalent to the first, but with different variables. The question at hand is how to bring both equations into the form of \frac{dx^{2}}{dt^{2}}+2\alpha \frac{dx}{dt}+\omega_{0}^{2}x=fcos\omega t. The solution involves using the formula \omega_{0}^{2} = c^2 + 4mk and integrating.
  • #1
Basheesh
4
0

Homework Statement



[tex]
m\frac{d^{2}x}{dt^{2}}+c\frac{dx}{dt}+kx=F_{0}cos\omega t\\
LC\frac{d^{2}V_{c}}{dt^{2}}+RC\frac{dV_{c}}{dt}+V_{c}=V_{0}cos\omega t
[/tex]These two equations are for two different physical phenomena. The first is for a mass moving along an x axis. The mass is affected by a springforce k, a dampener with constant c and an outer force F(t), here set to [tex]F_0cost(\omega t)[/tex].
Explanation of the second equation follows. The gist is that they are mathematically the same (I'm translating from danish, let me know if you need the rest).

a) show that both differential equations can be brought to the form:

1:
[tex]
\frac{dx^{2}}{dt^{2}}+2\alpha \frac{dx}{dt}+\omega_{0}^{2}x=fcos\omega t
[/tex]

Where [tex]\alpha \geq 0[/tex] and we assume [tex]\omega > 0[/tex]

Homework Equations



1:
[tex]
m\frac{d^{2}x}{dt^{2}}+c\frac{dx}{dt}+kx=F_{0}cos\omega t, LC\frac{d^{2}V_{c}}{dt^{2}}+RC\frac{dV_{c}}{dt}+V_{c}=V_{0}cos\omega t
[/tex]2:
[tex]
\frac{dx^{2}}{dt^{2}}+2\alpha \frac{dx}{dt}+\omega_{0}^{2}x=fcos\omega t
[/tex]

The Attempt at a Solution



I'm not even sure where to start with this.
So I'm thinking that I somehow need to use:
[tex]
\omega_{0}^{2} = c^2 + 4mk
[/tex]

and possible take the integral of the whole thing. But I am pretty lost.
 
Last edited:
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  • #2
which question are you having trouble? 1 or 2?
 
  • #3
I'm having trouble with a) for now. I edited out b to avoid confusion. But I might add it later, as I think I might have trouble with that one too.
 
  • #4
Use, [tex]x=Ae^{kt}+Be^{-kt}[/tex] to find the general solution and to find the particular integral [tex]x=C\cos\omega t+D\sin\omega t[/tex].
 
  • #5
But how does that help me writing the two equations in the form of (1)?
 

FAQ: Differential equations - transforming from one to another

What is the purpose of transforming differential equations?

The purpose of transforming differential equations is to make them easier to solve or to analyze. By transforming them into a different form, we can often simplify the equations and make them more manageable.

How do you transform a differential equation?

There are various techniques for transforming differential equations, depending on the specific equation and the desired outcome. Some common methods include substitution, change of variables, separation of variables, and Laplace transforms.

Can transforming a differential equation change its solutions?

Yes, transforming a differential equation can change its solutions. By changing the form of the equation, we may change the characteristics of the solutions or even the number of solutions. It is important to carefully consider the transformation and its effects on the solutions.

Is there a specific order in which differential equations should be transformed?

No, there is no specific order in which differential equations should be transformed. The transformation technique used will depend on the specific equation and the desired outcome. However, it is important to carefully consider the transformation and its effects on the solutions.

What are some real-world applications of transforming differential equations?

Transforming differential equations is used in many real-world applications, such as in physics, engineering, economics, and biology. For example, in physics, Laplace transforms are used to analyze electrical circuits and mechanical systems. In economics, differential equations can be transformed to model population growth or economic trends. In biology, transformation techniques can be used to study chemical reactions and population dynamics.

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