the speed of a boat is 5km/h in still water. it crosses a river of width 1 km along the shortest possible path in 15 min. the velocity of the river water is???

Question

the speed of a boat is 5km/h in still water it crosses a river
of width 1 km along the shortest possible path in 15 min the
velocity of the river water is???

Jyoti Pant · Accepted Answer

Solution:

$H e r e s p e e d o f b o a t v_{1} = 5 k m / h w i d t h o f r i v e r s = 1 k m t i m e t = 15 \min = 15 / 60 = 1 / 4 h o u r \sup p o s e s p e e d o f r i v e r w a t e r = v_{2} N o w w h e n a b o a t t e n d s t o c r o s s a r i v e r a l o n g a s h o r t e s t p a t h, t h e t i m e o f c r o s \sin g t = \frac{s}{\sqrt{{v_{1}}^{2} - {v_{2}}^{2}}} \frac{1}{4} = \frac{1}{\sqrt{5^{2} - {v_{2}}^{2}}} v_{2} = 3 k m / h$