A train slows down from 34 m/s to 4 m/s in 60 seconds. what is it's acceleration?

Acceleration = change in velocity / time

change in velocity = final velocity - initial velocity

because the object is slowing down, the acceleration will be negative.

acceleration = (4-34) / 60

acceleration = - 30 / 60

acceleration = - 0.5 m/s^2

answer : the train is accelerating at - 0.5 m/s^2