Final answer:
The acceleration of the automobile that slows down from 40 m/s to 10 m/s in 12 seconds is -2.5 m/s², indicating deceleration.
Step-by-step explanation:
The acceleration of an automobile that slows down from 40 m/s to 10 m/s in 12 seconds can be calculated using the formula for acceleration, which is:
Acceleration = (Final Velocity - Initial Velocity) / Time
By substituting the given values into the formula, we get:
Acceleration = (10 m/s - 40 m/s) / 12 s = -30 m/s2 / 12 s = -2.5 m/s2
This negative sign indicates that the automobile is decelerating, or slowing down, at a rate of 2.5 meters per second squared.