A boat which has a speed of 5km hr^(-1) in still water crosses a river of with 1 km along the shortest possible path in 15 minutes. Calculate the velocity of the river water.

A boat which has a speed of 5km hr^(-1) in still water crosses a river

1.	A boat which has a speed of 5km hr^(-1) in still water crosses a river of with 1 km along the shortest possible path in 15 minutes. Calculate the velocity of the river water.
Answer» Solution :The SITUATION is shown in Fig. of previous example OA=A, represents velocity of the river WATER. OB=B , represents velocity of the boat in still water which is `5km hr^(-1)` The boat crosses the 1km wide river ALONG the SHORTEST possible PATH OC in 15 minutes. Hence OC=R represents resultant velocity of the boat which is `(1km)/(15mt)=4km hr^(-1)` Here , `OB=AC =5 km hr^(-1), OC=4 Km hr^(-1),OA=?` In`DeltaOAC, OA=sqrt((AC)^(2)-(OC)^(2))=sqrt((5)^(2)-(4)^(2))=3` Here the velocity of the river water is `3km hr^(-1)`