Question
A stream of width d is flowing with velocity v. A person who can swim with speed V relative to water wishes to row straight across it. In what direction should he strike out and how long would it take him to cross the stream?
Solution
To row straight across the stream, the person must strike out at angle θ upstream, such that the resultant R of his own velocity and velocity of stream is perpendicular to velocity of stream.
∴
∴
The swimmer should dive at an angle
with normal to river and upstream.
Now the resultant velocity of swimmer and the stream is,
Therefore the time taken by swimmer to cross the river is,
∴
∴
The swimmer should dive at an angle
with normal to river and upstream. Now the resultant velocity of swimmer and the stream is,
Therefore the time taken by swimmer to cross the river is,
