A train starting from rest travels the first part of its journey with constant acceleration a, second part with constant velocity v and third part with constant retardation a, being brought to rest. The average speed for the whole journely is (7v)/(8). For what fraction of the total time, the train travels with constant velocity?

A train starting from rest travels the first part of its journey with

1.	A train starting from rest travels the first part of its journey with constant acceleration a, second part with constant velocity v and third part with constant retardation a, being brought to rest. The average speed for the whole journely is (7v)/(8). For what fraction of the total time, the train travels with constant velocity?
Answer» `1//2` `3//4` `5//3` `5//8` ANSWER :B