The one degree-of-freedom assembly of N four-bar linkages is composed by
2N+1 links of 1 m length with a uniformly distributed mass of 1 kg.
The system is under gravity effects (9.81 N/kg acting in the negative *y* direction).

This system is a typical example of mechanism that undergoes singular configurations. When the mechanism reaches the horizontal position, the number of degrees of freedom instantaneously increases from 1 to N+1.

The analysis to be performed is a dynamic simulation with a duration of 20 s.
Initially, the system (particularized for N=40) is in the position shown in the figure, and the velocity of the
*x*-coordinate of point B0 is 1 m/s.

The reference solution for this problem is the time-history of the position and velocity of point B0 (*x* and *y* coordinates). The maximun allowed errors are 1.0E-1 (low precission) and 1.0E-3 (high precission), measured with 400 output steps and a threshold value of 1.0E-3.

The following information is provided:

- Time-history of the position and velocity of point B0, as text data file: A02_solution_data.txt
- Animation of the system, as AVI movie (first 10 s): A02_solution_movie.avi
- Time-history of the position and velocity of point p1, as plot (first 10 s):