Ok, the equations were written in the test :
1/2 (0.5Kg) (V(0) ^ 2)
= (0.5 kg) (9.8m/s^2) ((-0.1m)sin30) + 1/2(400N/m)(-0.1m)^2
i had to "invent" a problem, that should be solved with the exact same equations.
the problem that i invented was described above.. unfortunatly, i choosed...