First, we need to convert the speed from km/h to m/s to use it in the equation. We have:
108 km/h = 30 m/s (approx)
The formula for acceleration is:
a = (v_f - v_i) / t
where a is the acceleration, v_f is the final velocity, v_i is the initial velocity, and t is the time taken. We know the initial velocity is 30 m/s (since the object is moving with a constant velocity before it starts to decelerate), the final velocity is 0 m/s (since the object comes to a stop), and the time taken is 15 s. Substituting these values into the formula, we get:
a = (0 - 30) / 15 = -2 m/s^2
The negative sign indicates that the acceleration is in the opposite direction to the initial velocity, which is deceleration. Therefore, the value of the acceleration is 2 m/s^2.