A student starts from point O on a straight walkway and moves strictly along the north–south line according to the following schedule:
• Walks 12 m north in 10 s,
• Then walks 5 m south in 4 s,
• Then walks 8 m north in 6 s,
• Then stands still for the next 5 s.
Assume the positive direction is towards the north.
(a) Draw a position–time graph for the entire 25 s motion, clearly labelling all key points.
(b) Using the data, calculate:
(i) the total distance travelled,
(ii) the net displacement from point O at the end of 25 s,
(iii) the average speed over the 25 s interval,
(iv) the average velocity over the same interval.
(c) Comment on the sign of the displacement and average velocity obtained, and state which of the four quantities in part (b) are scalars and which are vectors.