a river is flowing from west to east at speed 5m/min. a man on the south bank of river, capable of swimming at 10m/ min in still water wants to swim across the river to a point directly opposite in shortest time. what direction shoukd he swim in?

can u plz explain the meaning of this problem with the help of a diagram. n wt is rele to be found out.?i need this soon plz.

A i 

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 Ci--------B  In the diagram, let vector BA represents the velocity 'v' which men tries to travel with.CB vector represents direction of stream (from west to east).

So final velo of man is vector velocity of man + vel of water  = vector CB + vector BA = CA hence resultant direction of man becomes CA vector, which is desired direction i.e. across the river directly opposite to the point of start from south bank. OK?

Now CB = 5 (in magnitude) and BA = 10  (in magnitude ,

So, resultant speed CA = sqrt (10² + 5²) = sqrt (125) = 5v5

so angle with which it should swim = <B  where Cos B = CB/BA = 5/10 = 1/2 so B = 60 degrees (from the river bank)