v = a*t
a = v / t = 51,70 km/h / 12 s = 14,36 m/s / 12 s = 1,197 m/s^2
F = m * a = 20 kg * 1,197 m/s^2 = 23,94 N
s = 1/2 * a * t^2 = 1/2 * 1,197 m/s^2 * (12 s)^2 = 86,18 m
W = F * s = 23,94 N * 86,18 m = 2063 J
Auch einfacher zu errechnen über W = 1/2 * m * v^2