hi,

I am no expert on publications but at a first glance using the model seems ok to me, you use the same parameters to calculate the speed as you used in the model for the distance after all. I.e. S= a*x^2 +b*x+c and V=2*a*x+b - so a and b determine both.

The R-squared of 1 and the wobliness of the speed make me pause a bit. Are the position-time measurements sitting very closely on the parabola ? How do you calculate the numerical derivative of the data set? Maybe that is where the problem is.

regards