Pourrais t’on m’aider svp ?

Bonjour,
E = 1/2 Ă— m Ă— v^2
0.5 = 1/2 Ă— 0.0002(kg)Ă—v^2(m/s)
0.5 = 0.0001 Ă—v^2
V^2 = 0.5/0.0001
V^2 = 5000
V = racine de 5000
V ~71m/s
71 Ă— 3.6 ~255 km/h