u= coef de frecare
v = v_{0} + at
Ff = Gt
Ff = u * N
Gt = m * a
N = Gn
Gn = cos(α) * G = cos(α) * m * g
a = (u * N) / m = (u * Gn) / m = (u * G * cos(α)) / m
a = (u * m * g * cos(α)) / m
a = u * g * cos(α)
a = 0,05 * 10 * cos 15 = 0,48 m / s²
t = ( v-v_{0} ) / a
t = ( 36 - 18 ) / 0,48 = 37,26 s