Chapter 11.3, Problem 11.69P

In a water-tank test involving the launching of a small model boat, the model's initial horizontal velocity is 6 m/s and its horizontal acceleration varies linearly from -12 m/s² at $t=0$ to -2 m/s² at $t=t_1$ and then remains equal to -2 m/s² until $t=1.4$ s. Knowing that $v=1.8$ m/s when $t=t_1$ , determine (a) the value of t₁, (b) the velocity and the position of the model at $t=1.4$ s.