Answer:
The average acceleration is 8.06 m/s².
Step-by-step explanation:
It is given that,
Initial speed of the jet, u = 120 mph = 176 ft/s
Final velocity of the jet, v = 30 mph = 44 ft/s
Distance, d = 1800 ft
We need to find the average acceleration required of the airplane during braking. It can be calculated using third law of motion as :

a = acceleration



So, the average acceleration required of the airplane during braking is -8.06 ft/s². Hence, this is the required solution.