4. (a) What is meant by (i) velocity, and (ii) acceleration? (h) A lift, on its upward journey, starts from rest and accelerates for 5 s until it reaches a velocity of 2 m s-. After this, it moves at a constant speed for 10 s and then retards to rest after another 5 s. For its downward journey, it again starts from rest and accelerates for 10 s until it reaches a velocity of 3 m s". Then it retards to rest after another 10 s. Sketch the velocity-time graphs for both the upward and downward journeys made by the lift. Calculate (i) its acceleration during the upward journey; (ii) its retardation during the downward journey. (iii) What can you say about the areas under the two velocity-time graphs