physics
posted by pavatharani .
Between two stations a train acclerates uniformly at first, then moves with constant velocity and finally retards uniformly. If the ratio of the time taken be 1:8:1 and the max speed attained be 60km/h then what is the average speed over the whole journey?

avg velocity when accelerating or deaccelerating = 30km/hr
So assume t=10 hrs
first hour, distance=30km/hr*1hr
last hour, distnace=30km/hr*1hr
middle time, distance=60km/hr*8=480km
avg velocity=total distance/time=you do it. 
12km/hr