SPF

,Hi Xavier

1 I would advise extreme care with equations like this.

In this case it doesn't evaluate but if it did you would be re-defining the metre unit for mathcad & everything after this would be compromised.

Later you do define g as stack(...) which redefines the gravitational constant that is used later.

2 I'm a little confused as to what you need.

F.w is defined as:

But then you re-define it with

Mathcad can't understand this recursive form so better to use the same format as you have for t2 & t3 earlier.

{Looking carefully I note that it is F[w*(j) not F.w(j)}

Now that i have corrected for the change of g,

F.w has units of kg/s^2 but you are trying to add something with units of m/s^2

There is an error here somewhere but without knowing what the equations represent it is difficult to identify what that error is.

Regards

Andy