The speed of the boat is 3.6m/sec.
We know very well that when time is given and acceleration is constant and the question is asking for distance, we need to apply second equation of motion which is given by
S=ut+(1/2)at²
where u is the initial velocity and a is the acceleration and t is the time
So, we are given that key is released, means that initial it is in rest condition, so initial velocity(u)=0m/sec
Therefore
=>44m=0×t+(1/2)at²
=>(1/2)at²=44
=>(1/2)×9.8×t²=44(using a as acceleration due to gravity =9.8m/sec²)
=>9.8×t²=44×2
=>t²=88/9.8
=>t²=9sec²
=>t=3sec
The boat, moving at a presumably constant speed, then has 3.0 s to travel 11 m to the point of impact, which means its speed must be
v=(11/3)
=>v=3.6m/sec
Hence, speed of boat if a key falls from a bridge into it is 3.6m/sec.
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