An object moves along a straight line. ( i just dont understand part 3 and 4 )?

I'm not going to do your work for you, but unless I'm mistaken, its accelerating in the opposite direction of its initial velocity. Think of it this way: you throw a ball up in the air. As gravity pulls it down, and it reverses direction, how long does it take for it to p through the space where you first threw it?