What is the acceleration of a car moving at a speed of 72 km / h if it stops after 20 seconds?

Given:

V0 = 72 km / h = 20 m / s – initial vehicle speed;

V1 = 0 m / s – vehicle speed after a time interval t;

t = 20 seconds – time span.

It is required to determine the vehicle acceleration a (m / s ^ 2).

We find the acceleration of the car by the formula:

a = (V1 – V0) / t = (0 – 20) / 20 = -20 / 20 = -1 m / s ^ 2. A negative sign for acceleration means that the vehicle’s speed has decreased over time, that is, there has been an even slow motion.

Answer: the acceleration of the car is -1 m / s ^ 2.