Question

A man can swim in still water at a speed of 5 km/hr. He wants to cross a river 6 km wide, flowing at the rate of 4 km/hr. If he heads in a direction making an angle of 127° with stream direction, then he will reach a point on the other bank







correct and fastest answer will be marked as brainlest anwes​

Answer 1

Answer:

Explanation:

I think this question comes from vectors topic of physics

$Velocity of man in still water(v_{m}) = 5 km/hr$

$Length of River (d) = 6 km$

$Velocity of River (v_{r} ) = 4 km/hr$

Angle (@) = 37 degree w.r.t direction of swimmer

Now total velocity of swimmer =  5(3)-6 = 9 km/hr

Now time to reach opposite point = 6/9 = 2/3

Answer 2

Answer: Approximately the man took 1 and half hours to swim across the river.

Explanation:

Step 1: Given data

Velocity of man swimming, v = 5 km/hr

Width of the river, d = 6 km

Speed of the stream of river, u = 4 km/hr

Angle made between man swimming and stream, Ф = 127°

Step 2: Find the resultant

The resultant velocity of man due to stream of river is given by the formula

$V = \sqrt{(v^2 + u^2+2vucos\phi)}\\V = \sqrt{5^2+4^2+ 2X5X4Xcos127}\\V = \sqrt{16.93}\\V = 4.11 \hspace{2}km/s$

Therefore the resultant velocity of man swimming in the river  = 4.11 km/s

Step 3: Find time taken to cross the river

We know,

distance $d = velocity X time$

$therefore \hspace{5} time \hspace{5} t = \frac{d}{V}\\t = \frac{6}{4.11}\\t = 1.46 \hspace{2} hours$

Therefore approximately the man took 1 and half hours to swim across the river.

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