Answer: 11,429 seconds.
Step-by-step explanation: Initially, the object is moving away from the origin in the positive x-direction but decelerating at constant rate until it reaches rest and then, the objects returns to the origin with a constant acceleration. By substituting the position equation of an object accelerating at constant rate, the following expression is found:
[tex]0 = 0 + (40 m/s)\cdot{t}+\frac{1}{2}\cdot{-3.5\frac{m}{s^{2}}\cdot{t}^{2}[/tex]
Which is a second-order polynomial. The time can be found easily by applying the General Second-Grade Equation, whose two roots are presented below:
[tex]t_{1} = 0, t_{2} \approx 11,429[/tex]
The second roots contains the answer.
