Schaum's Outline of Theory and Problems of Beginning Calculus

142 RECTILINEAR MOTION AND INSTANTANEOUS VELOCITY[CHAP. 1818.14 Two particles move along the x-axis. Their positions f(t) and g(t) are given by f(t) = 6t - t2 andg(t) = t2 - 4t.(a) When do they have the same position? (b) When do they have the same velocity? (c) When they have thesame position, are they moving in the same direction?18.15 A rock is dropped and strikes the ground with a velocity of -49 meters per second. (a) How long did itfall? (b) Find the height from which it was dropped.18.16 A ball is thrown vertically upward from the top of a 96-foot tower. Two seconds later, the velocity of theball is 16 feet per second. Find: (a) the maximum height that the ball reaches; (6) the speed of the ballwhen it hits the ground.