As the velocity of the body is uniform,
Thus, the change of displacement in equal interval time remains constant.
The graphical representation of displacement and time for the uniform motion is,
From the diagram, the velocity of the particle from origin to the point A,
The velocity is,
The velocity of the body from A to B is,
Thus, the line in the graph passing through the origin, A and B is representing the motion of the body moving with the uniform velocity.