Resposta :
vf=vo+vot+gt^2/2
15=10+10t+10t^2/2
30=10+10t+10t^2
10t^2+10t-20=0
dividindo tudo por dez
t^2+t-2=0
delta=b^2-4ac
delta=1^2-4.1. (-2)
delta=9
t=-b+/- raiz de delta/2a
t=-1+/-3/2
t=2/2
t=1s
h=gt^2/2
h=10.1^2/2
h=5m
15=10+10t+10t^2/2
30=10+10t+10t^2
10t^2+10t-20=0
dividindo tudo por dez
t^2+t-2=0
delta=b^2-4ac
delta=1^2-4.1. (-2)
delta=9
t=-b+/- raiz de delta/2a
t=-1+/-3/2
t=2/2
t=1s
h=gt^2/2
h=10.1^2/2
h=5m