A tennis ball is shot vertically upward in an evacuated chamber inside a tower with an initial speed of 20.0 m/s at time t = 0 s. Reference: Ref 2-5 What is the magnitude of the acceleration of the ball when it is at its highest point? 3.13 m/s2 19.6 m/s2 9.80 /s 2 4.90 m/s2 zero m/s2