To find the time taken to travel a distance, we can use the formula:
Time = Distance / Speed
Given that the distance is 400 meters and the speed is 8 m/s, we can calculate the time taken as follows:
Time = 400 meters / 8 m/s = 50 seconds
Therefore, it would take 50 seconds for the train to travel a distance of 400 meters at a constant speed of 8 m/s.