1.

Speed of a man in water is 5 km ther, mantories to cross a vive filowing towardscast at 3km/hr of width Toom.find the Shortest time in which man crossesriver.Aut what angle from flow velocity manShould swim to reach directly opposite PointMan starts swimming forum Point A makingS3 angle with flow velocity. Find thePosition where he will reach also findthe time.​

Answer»

\huge \underline \green{\sf{ Answer :- }}

a. Velocity of man with respect to river water, v=5kmh−1. This is greater than the river flow velocity. Therefore, he can cross the river directly (along the shortest PATH or no drift CONDITION from flow velocity). The ANGLE of swim,

θ=2π+sin−1(vu)

= 90o+sin−1(vu)

= 90o+sin−1(53)

=90o+37o

= 127o w.r.t. the river flow or 37o w.r.t. the perpendicular in upstream direction

  • b. RESULTANT velocity or velocity of mass will be vm = v2 −u2

= 52−32

=4kmh−1

\small \underline  {\sf{In \  the \  direction \  perpendicular  \ to \  the  \ river \  flow. }}

  • c. time taken to cross the river

t = d/ v2−u2d

= 1km / 4kmh ^ −1

= 1 / 41h

\small \underline  {\sf{ q \ =  \ 15min}}



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