A student starts at the origin of a straight east–west road. First, she walks 20m due east in 10s, halts for a moment, and then walks 30m due west in 15s. The motion may be treated as uniformly accelerated only within each individual leg.
(a) Find the displacement of the student from the origin after (i) the first leg and (ii) the complete trip.
(b) Calculate the average velocity for the whole 25s motion.
(c) For each leg separately, state with reasons whether the instantaneous velocity and the acceleration can be positive, negative or zero. (Take the eastward direction as positive.)