Respostas

2014-08-09T16:33:48-03:00
74 km/h / 3,6 ≈ 20,55 m/s

S = So + V * t
80 = 0 + 20,55t
t = 80/20,55
t ≈ 3,8 s
2014-08-09T18:13:14-03:00
Converte km/h para m/s  74km/h ÷ 3,6 = 20,55 

v = Δs
       Δt

20,55 = 80
            Δt

20,55Δt = 80

Δt = 80  
       20,55

Δt = 3,89