Question

A river of width 200m flows at $5{ms}^{-1}$. A man crosses the river in the shortest time of 25s. If there is no flow and swims with the same velocity, the time taken to cross the river is :

• A. $\frac{200}{5\sqrt{3}}s$
• B. 20 s
• C. 25 s
• D. $25\sqrt{2}s$

Answer 1

The correct option is C 25 s

Solution In shortest time, the velocity of

the swimmer wrt to the river

will be directed towards the

other bank, then it there is

no flow,the swimmer will be

headed in the same direction

with velocity. So the time taken

to cross the river will be same

i.e, 25s as the flow velocity is

perpendicular to the direction of Matier

of the swimmer wrt river.

option - c is correct.