JEE Mains · Physics · STD 11 - Motion in plane
- JEE Mains 2025
- Easy
- MCQ
A river is flowing from west to east direction with speed of \(9 \mathrm{~km} \mathrm{~h}^{-1}\). If a boat capable of moving at a maximum speed of \(27 \mathrm{~km} \mathrm{~h}^{-1}\) in still water, crosses the river in half a minute, while moving with maximum speed at an angle of \(150^{\circ}\) to direction of river flow, then the width of the river is :
Pick an option to check your answer.
Answer & Solution
Correct Answer
(B) 112.5 m
Step-by-step Solution
Detailed explanation
\(\therefore \mathrm{V}_{\perp}=\) river flow \(=27 \times \cos 60^{\circ}=\frac{27}{2} \mathrm{~km} / \mathrm{hr}\).
Time taken \(=30 \mathrm{sec}\).
\(\therefore \mathrm{S}=\mathrm{Vt}=\frac{27}{2} \times \frac{5}{18} \times 30 \mathrm{~m}=112.5 \mathrm{~m}\)
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