Question

define relative velocity of an object with respect to the another object draw the position time graph for the object moving along a straight line when the relative velocity is zero and when the relative velocity is positive

Answer 1

Zero relative velocity means the two objects are either stationary (both), or they are separated by the same displacement all the time. That also means that they both have the same speed, velocity and acceleration. They move in the same direction. So the acceleration - time graph will be exactly same for both.