AIIMS2018Physics-Fluid Mechanics

AIIMS 2018 Physics Torricelli's Theorem MCQ Question

Type: MCQ-conceptual-Medium-Class 11

A wide vessel with a small hole at the bottom is filled with water (density ρ₁, height h₁) and kerosene (density ρ₂, height h₂). Neglecting viscosity effects, the speed with which water flows out is:

A

[2g(h1+h2)]1/2[2g(h_1 + h_2)]^{1/2}

B

[2g(ρ1h1+ρ2h2)]1/2[2g(\rho_1 h_1 + \rho_2 h_2)]^{1/2}

C

[2g(h1+h2(ρ2ρ1))]1/2\left[2g\left(h_1 + h_2\left(\frac{\rho_2}{\rho_1}\right)\right)\right]^{1/2}

D

[2g(h1+h2(ρ1ρ2))]1/2\left[2g\left(h_1 + h_2\left(\frac{\rho_1}{\rho_2}\right)\right)\right]^{1/2}

Correct Answer

Option C

Detailed Explanation

To determine the speed of water flowing out of the hole, we apply Torricelli's theorem, which states that the speed vv of fluid exiting a hole under the influence of gravity is given by v=2ghv = \sqrt{2gh}, where hh is the effective height of the fluid column above the hole. In this scenario, the effective height hh is influenced by both the water and kerosene columns, leading to the expression h=h1+h2(ρ2ρ1)h = h_1 + h_2 \left( \frac{\rho_2}{\rho_1} \right), where h1h_1 is the height of water and h2h_2 is the height of kerosene.

Option A is incorrect because it does not account for the different densities of the fluids. Option B mistakenly combines the heights without considering the density ratio. Option D misrepresents the relationship between the densities and heights, leading to an incorrect effective height. Thus, option C correctly incorporates the density ratio, yielding the proper effective height for calculating the exit speed of water.

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