A man can swim with a speed of $4.0\; km/h$ in still water. How long does he take to cross a river $1.0\; km$ wide if the river flows steadily at $3.0\; km/h$ and he makes his strokes normal to the river current? How far down the river does he go when he reaches the other bank ?
A man can swim with a speed of $4.0\; km/h$ in still water. How long does he take to cross a river $1.0\; km$ wide if the river flows steadily at $3.0\; km/h$ and he makes his strokes normal to the river current? How far down the river does he go when he reaches the other bank ?
Speed of the man, $v_{ m }=4 \,km / h$
Width of the river $=1 \,km$
Time taken to cross the river $=\frac{\text { Width of the river }}{\text { Speed of the river }}=\frac{1}{4}\, h =\frac{1}{4} \times 60=15\, min$
Speed of the river, $v_{ T }=3 \,km / h$
Distance covered with flow of the river $=v_{ r } \times t$ $=3 \times \frac{1}{4}=\frac{3}{4} \,km$
$=\frac{3}{4} \times 1000=750 \,m$
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