posted by Mary .
Two girls are at the same point on one side of a river that is 40m wide with a current flowing at 1.00m/s. Simultaneously, the dive into the water in an attempt to swim to the other bank of the river directly across from where they started. Both swim at 2m/s relative to the water, but Girl A directs herself so that her net motion takes her straight across while Girl B keeps her body perpendivular to the current and consequently lands downstream. After landing she runs along the shore to where Girl A landed at a speed of 6 m/s. Which girl arrives first and by how much?
Girl Two, is swimming up stream at an angle of arcsin(1/2) or 30 degrees. So she takes time 40/2*.866seconds to get across, or 23.09 seconds to get across. check that math.
Girl one, takes 20 seconds to get across, but then it takes her distance downstream at running. Distance downstream=20sec*1m/s=20m
total time= 20/6+20=23.3 seconds
So you better fine tune my calcs.