A swimmer wishes to cross a river 500m width flowing at a rate u. his speed w.r.t. still water is v. for this he makes an angle `theta` with the vertical as shown in the given figure then:

Options

A. to cross the river in minimum time `theta=0^(@)`
B. to cross the river in minumum time, `theta=30^(@)`
C. for u=3km/hr and v=5km/hr, the time taken to cross the river in minimum time will be 6min.
D. for u=3 km/hr and v=5km/hr, the time taken to cross the river in minimum time will be 3min.

Answer

a,c

Explanation

`t=((d)/(ucos theta))` for minimum time `theta=0`.