(a) Define (i) distance, (ii) displacement, and (iii) average speed.
(b) A cyclist rides the first 3km of a straight road at 15kmh−1 and the next 3km at 5kmh−1. Without performing any detailed calculation, state whether the average speed for the whole 6km journey will be closer to 5kmh−1 or to 15kmh−1. Give a reason for your answer.
(c) Explain why simply taking the arithmetic mean (15+5)/2 does not give the correct average speed for this journey.