Question

Give one example each of motion when (i)Acceleration is positive (ii)Accleration is negative (iii)Acceleration is zero

Answer 1

1- acceleration is zero
     
      An example would be a ball tied to an elastic. At first it is slowing down while traveling in the positive direction until it reaches zero velocity and then speeding up in the negative direction, all the while traveling with constant acceleration in the negative direction

2- accleration of negative and positive

the object is moving in the negative direction (i.e., has anegative velocity) and is slowing down.