Solving the problem mathematically,
Initial velocity of the ball 12m/s
Final velocity 0m/s
Travel time 36s
Assuming the velocity follows a straight line, then the slope of the curve is equal to the rate of change of velocity (acceleration)
ie taninv(dv/dt) since it is linear taninv(12/33)= 0.33 m/s^2 deceleration.
If in case the velocity doesn’t follow the linear path acceleration= d(velocity profile)/dt. ie the first order differentiation of velocity is the acceleration.