A ball is thrown vertically upwards at 19.6 m/s. For its complete trip (up and back down to the starting position), its average speed is:

Explanation

The following is the solution: We are first going to find time using the formula: v = u + at where: v = final velocity (zero at the highest point) u = initial velocity (19.6 m/s upwards) a = acceleration due to gravity (-9.8 m/s^2, negative because it acts downward) t = time to reach the highest point 0 = 19.6 - 9.8t Solving for t: t = 19.6 / 9.8 t = 2 seconds Assuming vertically upward & downward motions are identical with respect to time & distance covered by the given ball, the required average speed of the ball during its travel up and back down to the starting position = (total travel-distance)/(total travel time) = 2*(19.6 m)/[2*(2 s)] = 9.8 m/s Hence option B is correct.