A scooterist rides along a straight road covering the same distance twice—first from town A to town B and then back to town A—but at two different constant speeds. Answer the following questions about the journey without performing any numerical calculation.
(i) Define average speed and average velocity for the complete round trip in words only.
(ii) Explain qualitatively why the numerical value of the average speed for the round trip cannot be the simple arithmetic mean of the two individual speeds used on the onward and return journeys.
(iii) Discuss, with reasons, whether the average velocity for the entire journey is zero, positive, or negative.
(iv) Using logical argument (no algebra needed), justify why an average taken over equal distances but unequal speeds is closer to the lower of the two speeds.