The position-time graph for non-uniform motion is _ a straight line.

Explanation

The graph for uniform motion of a body is shown in the figure. The graph is inclined to time axis at an angle `theta`.
Therefore, slope of graph is

`m = tan theta = (PR)/( QR) = ( x _(2) - x _(1))/( t _(2) - t _(1)) = v.`
It means slope of position -time graph gives the velocity of the particle.