Answer:
34.3 m/s
Explanation:
The ball is in free-fall, so it undergoes constant acceleration. The motion can be modeled using kinematic equations, also known as SUVAT equations. The equation we will use is:
v = u + at
where
At the maximum height, the final velocity is v = 0 m/s. The time is t = 3.5 s. Taking up to be positive, the acceleration is a = -9.8 m/s². Solving for the initial velocity:
v = u + at
0 m/s = u + (-9.8 m/s²) (3.5 s)
u = 34.3 m/s
The ball was thrown at 34.3 m/s.