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JEE Main 2025 (2 Apr, Shift 1) · Pressure in a Fluid

Pressure in a Fluid question from JEE Main 2025 (2 Apr, Shift 1)

Q6JEE Main 2025 · 2 APR · SHIFT 1Medium

Pressure in a Fluid

A vessel with square cross-section and height of 6 m is vertically partitioned. A small window of 100 cm2100\text{ cm}^{2} with hinged door is fitted at a depth of 3 m in the partition wall. One part of the vessel is filled completely with water and the other side is filled with the liquid having density 1.5×103 kg/m31.5 \times 10^{3}\text{ kg/m}^{3}. What force one needs to apply on the hinged door so that it does not get opened? (Acceleration due to gravity =10 m/s2= 10\text{ m/s}^{2})

Numerical answer type. Work it out, then open the answer.

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Answer: 150

  1. Both sides are full (6 m), so the door at depth 3 m feels pressure from each liquid.
  2. Net pressure: ΔP=(ρ2−ρ1)gh=(1500−1000)×10×3=1.5×104 Pa\Delta P = (\rho_2 - \rho_1) g h = (1500 - 1000)\times10\times3 = 1.5\times10^4\text{ Pa}.
  3. F=ΔP A=1.5×104×100×10−4=150 NF = \Delta P\, A = 1.5\times10^4\times100\times10^{-4} = 150\text{ N}
  4. So the force needed is 150 N.
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