Write the expression for the velocity of the ball.
Write the expression for the acceleration of the ball.
Let the time in timer 1 be, the time in timer 2 be . Calculate the time interval.
The displacement is equal to the length of the section.
Substitute 4 foot for the displacement and for time interval in the equation (1).
Substitute for v and for time interval in the equation (2).
Therefore, the acceleration of the ball is .