Question

3.
2 marks
A river 1 km wide is flowing at a rate of 3 km/h and there is a swimmer having velocity of
4 km/h in still water. In what direction should the swimmer strike out in order to reach the
opposite bank of the river in shortest time interval? Calculate the time interval for
the swim.
ubiective​

Answer 1

Answer:

The swimmer should always head towards the point just across the river. That is his/her velocity wrt river is always perpendicular to the river flow. This is the way for the swimming across a river in minimum time duration. Then the time taken to cross = 1 km / 4 kmph = 1/4 hour = 15 min.