The speed of a boat is 5 km/h in still water. It crosses a river of width 1.0 km along the shortest possible path in 15 min. The velocity of the river water is (in km/h) (a) 5 (b) 1 (c) 3 (d) 4

Answer: (c). Shortest path: resultant velocity is straight across, vres = 1/0.25 = 4 km/h. vr = √(5² - 4²) = 3 km/h So the answer is (c) 3.

The speed of a boat is 5 km/h in still water. It crosses a river of… | NEET 1998 (AIPMT)

Q29NEET 1998 · AIPMTEasy

Relative Velocity in Two Dimensions

The speed of a boat is $5\text{ km/h}$ in still water. It crosses a river of width $1.0\text{ km}$ along the shortest possible path in $15\text{ min}$ . The velocity of the river water is (in $\text{km/h}$ )

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Answer: (c)

Shortest path: resultant velocity is straight across, $v_{res} = \frac{1}{0.25} = 4\text{ km/h}$ .
$v_r = \sqrt{5^2 - 4^2} = 3\text{ km/h}$
So the answer is (c) 3.

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Relative Velocity in Two Dimensions question from NEET 1998 (AIPMT)

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