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JEE Main 2014 (9 Apr, Shift 1) · Impulse & Momentum Conservation

Impulse & Momentum Conservation question from JEE Main 2014 (9 Apr, Shift 1)

Q16JEE Main 2014 · 9 APR · SHIFT 1Medium

Impulse & Momentum Conservation

Water is flowing at a speed of 1.5 ms ${}^{-1}$ through a horizontal tube of cross-sectional area 10 $-$ 2 m2 and you are trying to stop the flow by your palm. Assuming that the water stops immediately after hitting the palm, the minimum force that you must exert should be (density of water = 103 kgm ${}^{-3}$ ).

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Answer: (b)

Mass hitting palm per second $= \rho A v$ ; all its momentum is destroyed.
$F = \rho A v^2 = 10^{3} \times 10^{-2} \times (1.5)^2$
$F = 10 \times 2.25 = 22.5$ N
So the answer is (b) 22.5 N.

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