Question

The speed of boost is 15km/h in still water. It crosses a river of width 1km along the shortest possible path in 15min. The velocity of the river water is

Answer 1

Given - v=15km/hr S=1km t=15/60 hr.

From second eq . Of motion 1=1/2×a×(15/60)^2

a=8m/s^2

From first eq . Of motion

15= u+8×15/60

Hence u=13km/hr

Answer 2

Answer:

The velocity of river stream is 3 km/hr.

Explanation:

The speed of the boat along the shortest possible path

$AB = \frac{1}{\frac{15}{16} } = 4 km/hr$

Now, The velocity of river water

$V = \sqrt{5^{2}-4^{2} } = \sqrt{25-16} = \sqrt{9} = 3 km/hr$

Please refer the attachment!