A body moves along a straight line as follows: it travels from its starting point to a position 20 m away in 4 s with uniform motion, then remains at that position for the next 3 s, and finally returns uniformly to a position 5 m away from the starting point in the following 5 s.
(i) Draw a neat, labelled displacement–time graph for the complete motion using a convenient scale.
(ii) Using the graph, state the time intervals during which the velocity of the body is (a) positive, (b) zero, and (c) negative. Explain how you arrived at your answer in terms of the slope of the graph.
(iii) Compare the magnitudes of the velocity during the first 4 s and during the last 5 s. Which interval shows the greater speed of movement? Support your answer with suitable calculations from the graph.