Question 32147
a)s(t)=-16t^2+64t+0
b)s(1)=-16(1)^2+64(1)=-16+64=48 ft.
c)When it hits the ground the seight above the ground is zero.
  -16t^2+64t=0
  -16t(t-4)=0
  t=0 or t=4
The ball is on the ground at time=0 and at time t=4
Cheers,
Stan H.