Properties of Matter 4 Question 10
12. Consider a thin square plate floating on a viscous liquid in a large tank. The height $h$ of the liquid in the tank is much less than the width of the tank. The floating plate is pulled horizontally with a constant velocity $u _0$. Which of the following statements is (are) true?
(2018 Adv.)
(a) The resistive force of liquid on the plate is inversely proportional to $h$
(b) The resistive force of liquid on the plate is independent of the area of the plate
(c) The tangential (shear) stress on the floor of the tank increases with $u _0$
(d) The tangential (shear) stress on the plate varies linearly with the viscosity $\eta$ of the liquid
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Answer:
Correct Answer: 12. (b)
Solution:
- Surface energy, $E=\left(4 \pi R^{2}\right) T$
$$ \begin{aligned} & =(4 \pi)\left(1.4 \times 10^{-3}\right)^{2}(0.11) \\ & =2.7 \times 10^{-6} J \end{aligned} $$
$\therefore$ Correct option is (b).
