In a track competition, two athletes, Sipho and Thabo, are running at constant speed of 8 ms-1. Thabo is in front and 120 m from the finishing line, whilst Sipho is 10 m behind Thabo. What is the minimum acceleration that Sipho needs in order to win? Express your answer in m/s2

Aparticle's position is given by x = 3.00 - 9.00t + 3t2, in which x is in meters and t is in seconds. (a) what is its velocity at t = 1 s? (b) is it moving in the positive or negative direction of x just then? (c) what is its speed just then? (d) is the speed increasing or decreasing just then? (try answering the next two questions without further calculation.) (e) is there ever an instant when the velocity is zero? if so, give the time t; if not, answer "0". (f) is there a time after t = 3 s when the particle is moving in the negative direction of x? if so, give the time t; if not, answer "0".