h=+15 m
v=+5 m/s
Ball hits the ground when h(t)=-15m
h(t)=-9.8t^2+vt+h
=>
-15=-9.8t^2+5t+15
9.8t^2-5t-30=0
Solve for t, using quadratic formula,
t=-1.513 or t=2.023
reject negative root due to context, so
t=2.023 seconds
2)
h(t)=-16t^2+20t+8
a. height before pitch is when t=0, or h(0)=8
b. highest point reached when h'(t)=-32t+20=0 => t=5/8 seconds
c. highest point is t(5/8)=-16(5/8)^2+20(5/8)+8=47/5=9.4 m
d. ball hits ground when h(t)=0 => solve t for h(t)=0
=> t=-0.3187 seconds or t=1.569 seconds.
Reject negative root to give
time to hit ground = 1.569 since ball was pitched.