Final answer:
The object experiences a negative acceleration of 4 m/s² as its velocity decreases from 65 m/s to 25 m/s in 10 seconds, with east being the positive direction.
Step-by-step explanation:
To determine the acceleration of an object when its velocity is changing, we use the formula: a = Δv / t, where a is the acceleration, Δv is the change in velocity (final velocity minus initial velocity), and t is the time over which the change occurs. In the case described, the object is moving east and its velocity changes from 65 m/s to 25 m/s in 10 seconds. The change in velocity (Δv) would be 25 m/s - 65 m/s, which is -40 m/s. Divided by the time interval of 10 seconds, this gives us an acceleration of -4 m/s². Since east is considered the positive direction, and the velocity is decreasing, the acceleration is negative. Therefore, the correct description of the acceleration is:
a) Negative acceleration of 4 m/s²