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NEET PHYSICSMechanical Properties of FluidMedium

Question

Two non-mixing liquids of densities ρ\rho and nρn\rho (n>1n>1) are put in a container. The height of each liquid is hh. A solid cylinder floats with its axis vertical and length LL. The length of the cylinder inside the denser liquid is pLpL (p<1p<1). The density of the cylinder is dd. The density dd is equal to:

A

[2+(n+1)p]ρ[2+(n+1)p]\rho

B

[2+(n1)p]ρ[2+(n-1)p]\rho

C

[1+(n1)p]ρ[1+(n-1)p]\rho

D

[1+(n+1)p]ρ[1+(n+1)p]\rho

Step-by-Step Solution

  1. Principle of Floatation: For a body floating in a fluid (or multiple fluids), the total weight of the body is equal to the total buoyant force (upthrust) exerted by the displaced fluids .
  2. Weight of Cylinder: Let AA be the cross-sectional area of the cylinder. The volume of the cylinder is V=ALV = AL. The weight of the cylinder is W=mg=(ALd)gW = mg = (ALd)g.
  3. Buoyant Force: The cylinder is partially immersed in the denser liquid (density nρn\rho) and partially in the lighter liquid (density ρ\rho).
  • Volume in denser liquid: V1=A(pL)V_1 = A(pL).
  • Volume in lighter liquid: Since the total length is LL, the remaining length is (LpL)=L(1p)(L - pL) = L(1-p). Thus, V2=AL(1p)V_2 = A L (1-p).
  • Total Buoyant Force (FBF_B) = Weight of displaced denser liquid + Weight of displaced lighter liquid. FB=(V1nρg)+(V2ρg)F_B = (V_1 \cdot n\rho \cdot g) + (V_2 \cdot \rho \cdot g) FB=A(pL)(nρ)g+AL(1p)(ρ)gF_B = A(pL)(n\rho)g + A L (1-p)(\rho)g
  1. Equilibrium Equation: W=FBW = F_B ALdg=ALpnρg+AL(1p)ρgALdg = ALpn\rho g + AL(1-p)\rho g Divide by ALgALg: d=pnρ+(1p)ρd = pn\rho + (1-p)\rho d=ρ[pn+1p]d = \rho [pn + 1 - p] d=ρ[1+p(n1)]d = \rho [1 + p(n - 1)] d=[1+(n1)p]ρd = [1 + (n-1)p]\rho

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from Mechanical Properties of Fluid. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSMechanical Properties of Fluidnonmixingliquidsdensitiescontainerheight

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