12. A baseball player throws a baseball straight up into the air, the ball leaving his hand at time t = 0.0 s. The ball reaches maximum height at t = 1.4 s. When will the baseball return to the height from which it was released?

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13. The acceleration of an object is zero. Which best describes the possible motion of the object?

12. Since the time of flight of the baseball follows a parabolic curve, the time of the ball to return to the height from which it was is exactly the same as the time for the ball to reach maximum height, so

1.4 + 1.4 = 2.8 s

13. If the acceleration of the object is zero, then the object is moving at a constant speed.

For the acceleration to be zero, it means the velocity is NOT changing. So the possibilities are, it is standing still, it is moving at a constant speed, or it is at the exact point of changing directions which is the same as momentarily standing still.