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Question #42132

Difficulty: 8/10 | 🟢 Free

The Question

A cylindrical tank of constant cross-sectional area A1A_1 contains an ideal, incompressible liquid of density ρ\rho. At the bottom of the tank is a circular orifice made of a material with a coefficient of linear thermal expansion α\alpha. The tank walls have zero thermal expansion. Initially (t=0t=0), the liquid is at a height HH above the orifice, and the orifice has an area A0A_0 such that A1=2A0A_1 = 2A_0. The system is heated such that the temperature of the orifice increases at a constant rate dTdt=c\frac{dT}{dt} = c. Assuming the liquid density remains constant, find the initial rate of change of the efflux velocity of the liquid, dv2dt∣t=0\left. \frac{dv_2}{dt} \right|_{t=0}.

Options

  • A.

    4αc332gH−2g3\frac{4\alpha c}{3\sqrt{3}} \sqrt{2gH} - \frac{2g}{3}

  • B.

    2αc32gH−g\frac{2\alpha c}{\sqrt{3}} \sqrt{2gH} - g

  • C.

    4αc332gH−g3\frac{4\alpha c}{3\sqrt{3}} \sqrt{2gH} - \frac{g}{3}

  • D.

    8αc332gH−2g3\frac{8\alpha c}{3\sqrt{3}} \sqrt{2gH} - \frac{2g}{3}

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Variable_Constraint

Develop pure symbolic logic skills by mastering algebraic constraints without relying on numerical data.

Concepts Behind This Question

Expansion of Cavities in Solids|Torricelli’s Efflux Velocity|Differential Calculus

Why This Question Is Tricky

Common Mistakes

This problem tests the coupling of time-varying geometry with fluid dynamics.

A common JEE trap is assuming A1≫A2A_1 \gg A_2, which incorrectly simplifies Torricelli's law to v2=2ghv_2 = \sqrt{2gh} and ignores the kinetic energy of the free surface.

Furthermore, students often fail to recognize that the efflux velocity v2(h,t)v_2(h, t) is a multivariable function of both the falling fluid level h(t)h(t) and the thermally expanding orifice area A2(t)A_2(t).

Correctly solving the problem requires applying the multivariable chain rule to simultaneously account for the kinematic drop in pressure head and the thermal expansion of the cavity.

Quick Facts About This Question

Question Information

SubjectPhysics
ChapterThermal Properties of Matter - Class 11 Part 2
ConceptExpansion of Cavities in Solids
Difficulty8
Cognitive Load7
Target Solve Time160 sec
AccessFree