21.5 ft/s^2
The formula for distance traveled under constant acceleration is
d = 0.5 AT^2
where
d = distance
A = acceleration
T = time
Solving for A, gives
d = 0.5 AT^2
2d = AT^2
(1) 2d/T^2 = A
The formula for velocity under constant acceleration is
V = AT
Solving for A, gives
V = AT
(2) V/T = A
Now setting equations (1) and (2) above equal to each other and solving for T:
V/T = 2d/T^2
TV = 2d
(3) T = 2d/V
Now substitute equation (3) into (2) above.
V/T = A
V/(2d/V) = A
V * V/2d = A
V^2/2d = A
Plug in values and calculate.
V^2/2d = A
(44 ft/s)^2/(2*45 ft) = A
(1936 ft^2/s^2)/(90 ft) = A
21.51111111 ft/s^2 = A
Rounding to 3 significant figures gives 21.5 ft/s^2
