A baseball is thrown home plate at 40m/s ... the batter hits the ball and sends it flying at 60 m/s in the opposite direction. If this hit only took 0.01 seconds, then the acceleration of the ball is

10,000 m/s²

Explanation:

If we say the + x direction is away from home plate, then the initial velocity is - 40 m/s and the final velocity is + 60 m/s.

Acceleration is the change in velocity over change in time:

a = Δv / Δt

a = (60 m/s - (-40 m/s)) / 0.01 s

a = 10,000 m/s²