A small boat travels along a straight stretch of a river. The motion of the boat relative to the river bank is described below, taking upstream (against the current) as the positive direction:
• For the first 5s it moves with constant velocity 4m/s upstream.
• It then accelerates uniformly for 3s until its velocity becomes zero.
• Without any pause, it continues to accelerate at the same magnitude but now in the downstream direction for another 3s.
• Finally, it travels with a constant velocity of 2m/s downstream for 4s.
(a) Draw the velocity–time graph for the entire 15s motion.
(b) Calculate the total displacement of the boat from its starting point after 15s.
(c) Find the total distance travelled by the boat in the same time interval.