(a) Define average speed and average velocity.
(b) A motorist travels 60km due north from town P to town Q and then immediately 60km due east to town R, taking a total time of 2h. Without performing any numerical calculation, state whether his average speed is greater than, smaller than or equal to the magnitude of his average velocity for the complete journey P→Q→R. Give a clear reason for your answer.
(c) Mention any two everyday situations in which the magnitude of average velocity of a moving object becomes zero while its average speed remains non-zero. Explain in each case why this happens.