A parachute on a racing dragster opens and changes the speed of the car from 85 m/s to 45 m/s in a period of 4.5 seconds. What is the acceleration of the dragster?
Acceleration is change in velocity over time. In this example it will be a NEGATIVE acceleration as the car slows.
(Vf-Vo ) / time = (45 - 85 m/s) / 4.5 s = - 8.89 m/s^2