In physics, acceleration is defined as the rate of change of the velocity of an object with respect to time. That is A = VF - VI /T;
Where A = Acceleration
VF = Final velocity = 20 km
VI = Initial velocity = 80 km
T= Time = 0.5 hr
A = (20 - 80)/ 0.5 = - 60/.5
A = - 120 Km/ hr^2
Therefore, the acceleration of the car is -120 km/hr^2.
Because the value is negative, the appropriate name that describe it is deceleration.
