A swimmer capable of swimming with velocity u relative to water jumps in a flowing river having velocity v. The man swims a distance d down stream returns back to the original position . Find out the time taken in complate motion .

Explanation

`t=t_("down") +I_(u p)`
` =(d)/( v+u ) +(d)/( u-v) = (2 du )/(u^2 -v^2)`