JEE Main 2014 · 9 Apr · Shift 1 · Physics Q3

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PhysicsSingle correct+4 / -1Question 3 of 90

Water is flowing at a speed of 1.5 ms $^{-1}$ through a horizontal tube of cross-sectional area $10^{-2}$ m $^2$ 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 $=10^3$ kgm $^{-3}$ ).

15 N

22.5 N

33.7 N

45 N

Answer and worked solution

Official answer: B

The palm must destroy the momentum brought per second:
$F=\rho Av^2=10^3\times10^{-2}\times1.5^2=22.5\text{ N}.$

Topics:Impulse and momentum Continuity equation

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JEE Main 2014 · 9 Apr · Shift 1, Physics question 3