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Class 11
Physics
Motion in a Plane
a man can swim with a speed of 4 0 km h in still w...

Question:
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?

Answer:

Speed of the man, v_m = 4 km/h

Width of the river = 1 km

Time taken to cross the river = width of the river / speed of the river

= 1/4 h = 15 minutes

Speed of the river, v_r = 3 km/h

Distance covered with flow of the river = v_r × t

= 3 x 1/4 = 3/4 km

= 3/4 x 1000 = 750 m

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Question:
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?

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Question: 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?

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Question:
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?