*I will be using “a” for acceleration, “V” for velocity and “t” for time
Acceleration is the change in velocity over a specific period of time. In our situation, that time is 10 seconds, as the velocity went from 15m/s to 0m/s in seconds. If we say that the formula for acceleration is:
a = V2-V1/t (where V2 is the final velocity, or 0m/s, and V1 the inital, or 15m/s)
We can plug in the numbers:
a = (0-15)m/s / 10s
a = -15m/s / 10s
a = -1.5m/s^2 — we notice here that the acceleration is negative, and thats because the car is decelerating (slowing down). If the car was accelerating, or speeding up, the acceleration would be positive.