A boat which has a speed of $5 \mathrm{~km} / \mathrm{hr}$ in still water crosses a river of width $1…

A boat which has a speed of $5 \mathrm{~km} / \mathrm{hr}$ in still water crosses a river of width $1 \mathrm{~km}$ along the shortest possible path in 15 minutes. Then what is the velocity of the river water in $\mathrm{km} / \mathrm{hr}$ ?
  1. 1
  2. 2
  3. 4
  4. 3

Solution



Speed along the shortest path $=\frac{1}{15 / 60}=4 \mathrm{~km} / \mathrm{hr}$
Speed of water $v=\sqrt{5^{2}-4^{2}}=3 \mathrm{~km} / \mathrm{hr}$ /

Asked in: JEE Mains - Motion In One Dimension - Test 4

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