Question 1196739
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Answer:  -2 m/s^2
This represents slowing down by 2 m/s per second
I.e. each second the boat's velocity has gone down by 2 m/s


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Work Shown:
vi = initial velocity = 15 m/s
vf = final velocity = 5 m/s
a = acceleration = unknown and what we want to solve for
t = number of seconds that elapsed = 5 seconds


Using one of the four kinematics equations gets us the following
vf = vi + a*t
5 = 15 + a*5
5-15 = 5*a
-10 = 5*a
5*a = -10
a = -10/5
a = -2


If you wanted, you can rewrite that original formula as
a = (vf - vi)/t
which is the same as saying
a = (finalVelocity - initialVelocity)/(endTime - startTime)
effectively we are using something very similar to the slope formula. This is because the acceleration is the rate of change of the velocity. 
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