Speed of boat= 30.0 m/s
Acceleration = -3.50 m/s2
Distance= 100 m
Let 'v' be the final velocity
We know that
2as = v² - u²
-2 × 3.5 × 100 = v² - (30)²
-700 = v² - 900
v² = 200
v = 10?2 (10× square root of 2)
v = 14.14 ( square root of 2 is 1.414 )
Answer is :
v = 14.14 or 10?2 is the velocity of the boat when it reaches the buoy
Now,
t = (v-u)÷a
t = ( 14.14 - 30 ) ÷ (-3.5)
t = 4.5 s
Answer is : t = 4.5 s

Speed of boat= 30.0 m/s
Acceleration = -3.50 m/s2
Distance= 100 m
Let 'v' be the final velocity
We know that
2as = v² - u²
-2 × 3.5 × 100 = v² - (30)²
-700 = v² - 900
v² = 200
v = 10?2 (10× square root of 2)
v = 14.14 ( square root of 2 is 1.414 )
Answer is :
v = 14.14 or 10?2 is the velocity of the boat when it reaches the buoy
Now,
t = (v-u)÷a
t = ( 14.14 - 30 ) ÷ (-3.5)
t = 4.5 s
Answer is : t = 4.5 s