Final answer:
The car's acceleration, which is actually a deceleration as the car slows down, is -2 m/s², found by dividing the change in velocity by the time interval.
Step-by-step explanation:
The student asks about the acceleration of a car that changes its speed as it moves towards and comes to a stop at a junction. To find the acceleration, one can use the formula a = Δv / Δt, where Δv is the change in velocity and Δt is the change in time. Given that the car's initial speed is 12 m/s and it comes to a stop in 6 seconds, the change in velocity is Δv = 0 m/s - 12 m/s = -12 m/s. The time interval is Δt = 6 s. Thus, the acceleration can be calculated:
a = Δv / Δt = -12 m/s ÷ 6 s = -2 m/s².
The negative sign indicates that this is a deceleration since the car is slowing down.