4. A mirror is part of sphere of diameter 9.3 cm. A boy stands 0.5 m away from the mirror<br />and is amused to see his image. Determine the height of the boy's image if he is 1.3 m<br />tall. Where does the boy find his image? Why do you think the boy is so amused at<br />seeing his image? (A ray diagram is required).

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".