physics

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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?

• physics -

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.

• physics -

12km/hr

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