A man wishes to swim across a river 400 m wide flowing with a speed of 3m/s, such that he reaches the point just in front on the other bank in time not greater than 100 sec. The angle made by the direction he swims and river flow direction is :

90º

127º

150º

143º

Solution:

Distance travelled in y-direction = 400 m

Time to cross = 100 sec

So, Speed in y-direction = 4 m/s

Speed in x-direction = 3m/s

So, angle = 90 +37 =127º

2 responses to “”

1. Why are we adding the two angles at the end?

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   • Because we need to find angle with direction of flow of river.

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