3.101: Sketching velocity–time graphs

A particle moves in a straight line with constant velocity $6\,\mathrm{ms}^{-1}$. At $t = 0$ it passes fixed point $A$. At $t = 5$ it suddenly changes direction and moves with a different constant velocity along the same line, returning to $A$ at $t = 15$. Sketch the velocity–time graph for the motion.

Another particle moves in a straight line with constant acceleration. At $t = 0$ it passes fixed point $B$ with velocity $-8\,\mathrm{ms}^{-1}$. It passes $B$ again at $t = 20$. Sketch the velocity–time graph.