How do we calculate time that we need for specific distance if we have non-constant acceleration. I have some formulas for other variable but don't have for time:
Speed at time: $$ v(t) = v_0+at+\frac{j(t^2)}{3} $$
Distance at time: $$ x(t)=x_0+v_0t+\frac{a(t^2)}{2}+\frac{j(t^3)}{6} $$
Acceleration at time: $$ a(t)=a_0+jt $$
What you have there is a cubic equation, so if you want to solve for a specific distance, you would take your formula for $x(t)$, subtract the specific distance you want to get a cubic equaling 0, and then you would use the cubic formula, one version of which is posted here: http://www.math.vanderbilt.edu/~schectex/courses/cubic/
Warning, its not pretty.