Question

A steamer crosses a river having a width of $240m$ which is flowing with a speed of $8m/s$. In order to cross the river along the shortest path, find the time of crossing the river. [velocity of steamer in still water is $10m{s}^{-1}]$.

Answer 1

$V_{s\omega }=10m{s}^{-1}$

$V_{\omega }=8m{s}^{-1}$

width=240 m

$t=\frac{width}{V_s}=\frac{width}{\sqrt{V_{s\omega }^2-{V_{\omega }}^2}}$

$t=\frac{240}{\sqrt{100-64}}=\frac{240}{6}=40s$