Final answer:
The deceleration of the car, which initially moves at 72 km/h and comes to rest in 8 seconds, is calculated to be -2.5 m/s² after converting the initial speed to meters per second and applying the formula for acceleration.
Step-by-step explanation:
To find the deceleration of the car, we use the formula for acceleration which is Δv/Δt, where Δv is the change in velocity and Δt is the change in time. The car is initially moving at 72 km/h, which we need to convert to meters per second for consistency in units. 72 km/h is equal to 20 m/s (since 1 km/h is approximately 0.28 m/s).
Since the car is brought to rest, the final velocity (vf) is 0 m/s. With the initial velocity (vi) of 20 m/s and time (Δt) of 8 s, we can calculate the deceleration as follows:
a = (vf - vi) / Δt
= (0 m/s - 20 m/s) / 8 s
= -20 m/s / 8 s
= -2.5 m/s^2
Therefore, the deceleration of the car is -2.5 m/s^2.