A boy walks along a straight track taken as the x-axis with the eastward direction treated as positive. He starts from the origin, reaches the +60m mark, and then returns to the +10m mark. The entire walk takes 80s. Answer the following questions in a logical sequence.
(i) Define distance, displacement, speed and velocity.
(ii) Using the data given, state the numerical values (with proper units) of the distance travelled and the displacement of the boy at the end of the walk.
(iii) Without performing further calculations, state whether the average speed for the walk will be numerically greater than, equal to, or less than the magnitude of the average velocity. Give a clear reason for your choice.