Respostas

2013-11-29T13:06:55-02:00
S = So + VoT + at²/2
0 = 20 + 5t²
t² + 4 = 0
t = 2
V = VoT + at
V = 0+10.2
V = 20 m/s.
Alternativa (B). 
2013-11-29T13:27:15-02:00
Torricele

v²=vo²+2.g.H
v²=o²+2.10.20
v²=400
v=raiz400
v=20m/s.