Q18 of 43 Page 85

A swimmer crosses the river along the line making an angle 45° with the direction of flow of the river. If the velocity of river is 5 ms–1 and time taken by him is 6 seconds to cross the width of river 60m, then find the velocity of swimmer w.r.t. to the river.

Velocity of river = 5 ms–1

Width of river = 60 m



Let the flow of river be along x-axis


Then, given that the swimmer crossed at an angle 45° time taken by the swimmer is 6 s.


Now,


Now, displacement is given by:



Also, the time taken is 6 s


So, the velocity with respect to a stationary observer



Now, the river has the velocity in x-direction =


So, the relative velocity of a swimmer with respect to the river




Now, the magnitude of the velocity =


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