Weylan is at the county fair playing some of the games. At one booth, he throws a 0.75-kg ball forward with a velocity of 21.0 m/s in order to hit a 0.50-kg bottle sitting on a shelf, and when he makes contact the bottle
goes flying forward at 20.0 m/s. What is the velocity of the ball after it hits the bottle?

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".