Question

Swimmer is at the point a on the south bank of a river of width 200m . he wants to cross the river so as to reach a point b on the north bank of the river such that the line ab makes an angle of 60° with the river flow . the speed of the swimmer in still water is 4m/s and the speed of the river current is also 4m/s . in what direction should he swim ? how much time will he take ?

Answer 1

Answer:

The man has to travel 1.5km perpendicular to the flow to cross the river.And the velocity of the man is at 60 degree with flow, so component of man's velocity perpendicular to flow is vSin60=5×

2

3

time taken will be

speed

distance

=

5×

2

3

1.5

=0.35hr.

so best option is B.