Answer:

Step-by-step explanation:
To determine the acceleration of the box, we can use the kinematic equation that relates initial velocity
, final velocity (v), acceleration (a), and time (t):

In this case, the box is coming to a stop, so the final velocity (v) is 0 m/s. The initial velocity
is 8.5 m/s, and the time (t) it takes to stop is 1.2 seconds.
The equation becomes:

Now, solve for (a):


The negative sign indicates that the acceleration is in the opposite direction to the initial velocity.
Therefore, the box decelerates (slows down) at a rate of approximately
when it hits the pillow.