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9.1 , fluid mechanics — Physics STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 SciencePhysics9.1 , fluid mechanics1 Mark
MCQ
A flat plate of area $0.1 \,m ^2$ is placed on a flat surface and is separated from it by a film of oil $10^{-5} \,m$ thick whose coefficient of viscosity is $1.5 N \,sm s ^{-2}$. The force required to cause the plate to slide on the surface at constant speed of $1 \,mm s ^{-1}$ is ............ $N$
  • A
    $10$
  • ✓
    $15$
  • C
    $20$
  • D
    $25$
✓

Answer

Correct option: B.
$15$
b
(b)

$F=\eta A \frac{v}{l}$

Substituting values,

$=1.5 \times 0.1 \times \frac{1 \times 10^{-3}}{10^{-5}}$

$=15 \,N$

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