The time taken by ball to fall back to Bill is,
[tex]t=\frac{2u}{g}[/tex]
Plug in the known values,
[tex]\begin{gathered} t=\frac{2(17\text{ m/s)}}{9.8m/s^2} \\ =3.37\text{ s} \end{gathered}[/tex]
Therefore, the time taken by ball to fall back is 3.37 s.
