Respuesta :

kikdddd
its 18 hope that helps
when he hit the ground then intial velocity is 0 and height is zero
h(t)=0
v0=0

h(t)=-4.9t^2+v₀t+h₀
-4.9t^2+0+70=0
-4.9t^2=-70
t^2=70/4.9
t^2=14.285
t=√14.285
t=3.7796 seconds
t=3.8sec