Question

A man can swim with a speed of `4kmh^(-1)` in still water. He crosses a river 1km wise that flows steadly at `3kmh^(-1)`. If he makes his strokes normal to the river current, how far down the river does he go when he reaches the other bank?

Answer 1

Time to cross the river, ` t= (width of river )/( speed of man ) = ( 1 km ) /( 4 km//h) = 1/4 = 15 min`
Didtance moved along the river in time ` t= v_r xx t =3 km // h xx 1/2 = 3/4 km = 750 m`.