Acceleration = (change in speed or direction) / (time for the change).
Change in speed = 60 ft/s
Time for the change = 10 s
Acceleration = (60 ft/s) / (10 s)
Acceleration = 6 ft/s²
(Acceleration of gravity is about 32.2 ft/s², so the people in the car are pulling about 0.19 of one G.)
