Read the statements carefully and answer all parts based on your understanding of the ideas involved in one-dimensional and two-dimensional motion.
(i) Define distance, displacement, average speed and average velocity.
(ii) Explain qualitatively, with the help of suitable examples, whether average speed can be (a) less than, (b) equal to, or (c) greater than the magnitude of average velocity.
(iii) A sprinter completes one full lap of a 400 m circular track in 100 s. Without performing any numerical calculation, state and justify the relation between her average speed and the magnitude of her average velocity for this lap.
(iv) Describe a specific journey in which the magnitude of average velocity is zero while the average speed is non-zero, and explain physically why this occurs.