Question

A boat can travel at a speed of 3 m/s on
still water. A boatman wants to cross the
river while covering the shortest possible
distance. In what direction should he row
with respect to the bank, if the speed of
the water is 4 m/s​

Answer 1

Explanation:

Given speed of boat in still water =13 m/min

speed of water =5 m/s

(a) To achieve minimum distance the boat must travel in the direction opposite to that of the flow of water.

So the net speed of boat=5−

60

13

=4.78m/s

We know t=

v

s

;where s= 78 m (as the width of the river is 78)

t=

4.78

78

=16.31s

(b) To achieve minimum time the boat must travel in the direction to that of the flow of water.

Thus speed of the boat=5.216 m/s

t=

5.216

78

=14.95s