A speedboat starts from rest and accelerates at +2.07 m/s2 for 7.00 s. At the end of this time, the boat continues for an additional 6.00 s with an acceleration of +0.523 m/s2. Following this, the boat accelerates at -1.55 m/s2 for 8.00 s. What is the velocity of the boat at t = 21.0 s?

Answer 1

The velocity at the end of the first interval is (2.07 m/s^2)*(7.00s) = 14.49 m/s

The velocity increases by an amount (0.523 m/s^2)(6.00s) = 3.14 m/s
during the second interval. This brings the velocity up to 17.63 m/s

During the third interval, the velocity decreases by (1.55 m/s^2)*(8.00 s) = 12.40 m/s
Now complete the final step. Subtract 12.40 from 17.63 m/s