# A Pendulum with spring instead of rod

1. Apr 17, 2017

### nneutrino

When we have solid rod instead of spring I can solve this problem in Microsoft Excel either with Euler´s method or Runge Kutta method, but that spring makes this problem hard for me.

2. Apr 17, 2017

### JoePhysics

That problem is a lot more complicated. Basically, instead of the one degree of freedom that you had for the simple pendulum (the angle), you have two (the angle, and the extension of the spring). The standard way to solve such a problem is to obtain the equations (note that I said it in plural) of motion with, say, Lagrangian mechanics. To keep this thread dedicated to its original title (Non-harmonic oscillation of pendulum) it would probably be better if you created a new thread with this question to keep the forum neatly organized.

3. Apr 17, 2017

### nneutrino

Hi,
Can you help me to find out appropriate numerical model of calculating position depending on time of special pendulum. It is basically gravity pendulum but we have a spring instead of rod. (picture)

4. Apr 17, 2017