Oversimplifying it a bit. Imagine a swimmer swims 5m/s and the current adds/subtracts 1m/s. The pool is 50m. No current each length should take 10s. Going with the current takes 8.3s and going against the current takes 12.5 seconds. 100m takes 20.8s instead of 20s. Why?
While the benefit/detriment ratio is 50-50 in terms of distance, it's not 50-50 in terms of time. You spend less time benefiting from the current because you are going faster.
Alternatively, if the race was a fixed 10seconds in each direction you would go 60m and 40m, making it equivalent.
Yes. Imagine a current flowing exactly as fast as you can swim and you must swim one lap with it and one against it. You cover the lap in half your normal time when it's helping you and then when it's against you you cannot _even_ cover a lap. Total time = infinity.
>you must swim one lap with it and one against it.
Lengths, not laps. A lap in running brings the runner around the track and back to where they started. A lap in swimming is from one side to the other and back again (100m). A length, from one side of the pool to the other, is 50m or half of a lap. If there is a current one length is different from another other, but the laps are identical.
Oversimplifying it a bit. Imagine a swimmer swims 5m/s and the current adds/subtracts 1m/s. The pool is 50m. No current each length should take 10s. Going with the current takes 8.3s and going against the current takes 12.5 seconds. 100m takes 20.8s instead of 20s. Why?
While the benefit/detriment ratio is 50-50 in terms of distance, it's not 50-50 in terms of time. You spend less time benefiting from the current because you are going faster.
Alternatively, if the race was a fixed 10seconds in each direction you would go 60m and 40m, making it equivalent.