check the picture below.
[tex]\bf h(t)=-16t^2+50t\implies 0=-16t^2+50t\implies 0=-t(16t-50)
\\\\\\
\begin{cases}
0=-t\implies &0=t\\
------\\
0=16t-50\\
50=16t\\
\frac{50}{16}=t\implies &\frac{25}{8}=t
\end{cases}[/tex]
it hits it twice, once at the beginning, 0 seconds, and when it hits the ground at the end.
