﻿ A river 100 m wide is running downwards at the rate of 1 km per hour and a swimmer who can swim at the rate of 3·6 km/hr wishes to reach a point just opposite. Along which direction should he strike and how long will he take to cross the river? from Physics Motion in A Plane Class 11 Manipur Board

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A river 100 m wide is running downwards at the rate of 1 km per hour and a swimmer who can swim at the rate of 3·6 km/hr wishes to reach a point just opposite. Along which direction should he strike and how long will he take to cross the river?

Given,

Width of the river = 100 m

Rate of flow of river = 1 km/hr

Rate of flow of swimmer = 3.6 km/hr

Let the swimmer dive at an angle  as shown in figure to reach the point B directly opposite to A.

From the fig., we have

∴

Therefore, the swimmer should dive at angle (90 + 16·14) =106·14° with the direction of flow.

Now,

Time taken to cross the river, t =

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