Answer:
a = (V2 - V1) / t average acceleration between points 1 & 2
V2 = speed at bottom = -4.8 m/s
V1 = 4.8 m/s speed when thrown, choosing upwards as positive
a = (-4.8 - 4.8) / .98 time upwards = time downwards
a = -9.6 m/s / .98 s
a = -9.8 m/s^2
4.5m questions
5.8m answers