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A boat which has a speed of 5km/hr in still water crosses a river of width 1km along the shortest possible path in 15 minutes. The velocity of the river water in km/hr is ?

A boat which has a speed of 5km/hr in still water crosses a river of width 1km along the shortest possible path in 15 minutes. The velocity of the river water in km/hr is ?

Grade:11

9 Answers

mohit sengar
39 Points
14 years ago

the velocity of the river is 3 km /h

aditya bhardwaj
33 Points
14 years ago

please explain how idont want the answer but how the answer comes?

Fawz Naim
37 Points
13 years ago

let the velocity of the river be x. the velocity of the river will be in the horizontal direction

velocity of boat in still water is 5km/hr. As the width of the river is 1 km and time taken by the boat to cross the river along the shortest path is 15 min therefore the velocity of the boat is=  1*60/15= 4km/hr

 according to the figure the velocity of the river is along  AB . By applying triangle law of vector addition the value of AB comes to be 3km/hr

1590_22392_line.jpg

karthik s
19 Points
7 years ago
how the boat go in the direction CA and river in AB pls explain the direction of river and moving boat
 
Himanshu Kumar
20 Points
7 years ago
As the boat crosses the river it experiences two forces one horizontal direction (by the river along AX) and another by the one who rows the boat (in the vertical ditection along AB) X A ------ v=3m/s
Preethi P Gowda
19 Points
7 years ago
The width of the river=1.0kmThe boat crosses the river in 15 minutes The resultant velocity of boat =1.0km/0.25h=4km/hVelocity of river=(5²-4²)½ =3km/h
Kanishka agrawal
19 Points
6 years ago
Given - v=5km/hr S=1km t=15/60 hr. From second eq . Of motion 1=1/2×a×(15/60)^2a=8m/s^2From first eq . Of motion5= u+8×15/60 Hence u=3km/hr
Rohan takmoge
13 Points
6 years ago
Velocity= distance /time
              = 1km /0.25 hr. ......(15 min=0.25hrs)
              = 4 km/hr 
The velocity of the river water is 4 km/hr
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yash singh
13 Points
5 years ago
Let V be the speed of boat and V’ be the speed of river. Let d be the width of river. Let T be the time taken. According to question V=5km/hr , d=1 km and T= ¼ hr. Now simply put these values in  the formula T= d/√V^2 + V’^2 . From here, V’ = 3km/hr.

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