Relative Velocity-Please Help me out

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A river is 20 m wide.River speed is 3 m/s.A boat starts with velocity 2âˆš2 m/s at angle 45Â° from the from the river current(relative to river).How far from the point directly opposite to the starting point does the boat reach the opposite bank?
(I am getting 10 m.....correct answer is 50 m)

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2 Answers

Vivek @ Born this Way ·2012-05-26 08:41:34

You would get 10m if you swim at angle of 45 degrees with the vertical AGAINST the current of river. Then the relative velocity would be 1 m/s , then in 10 seconds (the time to reach the other bank), it would travel 10 m. However, when you make it travel along the stream, the relative velocity would be 5 m/s, and hence the dist. 50m.