ok now i got it. So if it took 2 sec. to reverse the average velocity would be -60-60/2 and since acceration is always positive it would be 60 m/s squared?
A train travels due south at 60 m/s. It reverses its direction and travels due north at 60 m/s. What is the change in velocity of the train? Whats the average acceleration if it took 2 sec. to reverse.