Given:
The initial velocity of the boat is,
[tex]u=18\text{ ft/s}[/tex]The final velocity of the boat is,
[tex]v=0[/tex]The boat stops after,
[tex]t=9\text{ s}[/tex]If the acceleration is a, we can write,
[tex]v=u+at[/tex]Substituting the values we get,
[tex]\begin{gathered} 0=18+a\times9 \\ a=-\frac{18}{9} \\ a=-2ft/s^2 \end{gathered}[/tex]Hence the acceleration is -2 ft/s^2.
