If the southbound current is running @6mph along the shore and your northbound boat is running @6mph over the water you are not going anywhere. A speed over water greater than 6mph would be necessary to make any headway relative to the land.
How about this...................now you are heading south on the same river which is flowing @6mph. If you do NOTHING, you are at 6mph, at the mercy of the current. You can't even steer. In that case, you would have to power up and travel faster than the current in order to maintain steerage. And that is what is meant by the term "the slowest speed possible to maintain steerage OR 6mph."
|