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Hi !

I currently teach Mechanics to students that are typically 18-19 years old.
I used this year Algodoo for one activity in small classrooms (about 25 students) ; because of the interest that students have found in this approach, I would like to develop more activities based on Algodoo.

In particular, I am interested in comparing the results of analytical models of single-degree-of-freedom oscillating systems (free vibrations and forced vibrations) to those obtained with Algodoo.
I tried some of those I have in mind, and most of them work quite properly (ie agreement between theory and results from simulation). Nevertheless, I have two problems :
- study of free vibrations of a mass linked to two springs (see ex5.6_v3.phn)
- study of transmissibility of vibrations (ie car suspension) (see ex7.2.phn)
Whereas I checked the theoritical results I used to describe these problems, I was not able to find comparable results to those of the simulation with Algodoo.
This is why I am wondering whether the behaviour of the simulated movement in Algodoo is reliable from a quantitative point of view. Any comment on this would be gratefully acknowledged.

umm, start from using "perfect geoms" like circles and boxes instead of polygons.
make everything 0 friction and restitution.
turn off air.

Kilinich wrote:umm, start from using "perfect geoms" like circles and boxes instead of polygons.
make everything 0 friction and restitution.
turn off air.

Thanks for your suggestion. I'll try with simple geoms, but why would it change something ?

Btw, I clearly see while monitoring the motion that damping (due to springs or friction, be it with air) is not a problem because the motion has a constant amplitude (no decay of amplitude with time).
For example in the case ex5.6.phn, I have solved the equation of motion with a rk45 scheme and the period of movement is two times larger (roughly) than that given by Algodoo, which seems to indicate that there is "something" independant from damping.
But I do not what up to now !
Thanks for your help

The reason why simple geometries work better than polygons is because of the way algodoo collision detection system works.