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NEET PHYSICSOscillationsMedium

Question

A rectangular block of mass mm and area of cross-section AA floats in a liquid of density ρ\rho. If it is given a small vertical displacement from equilibrium, it undergoes oscillation with a time period TT. Then:

A

TρT \propto \sqrt{\rho}

B

T1AT \propto \frac{1}{\sqrt{A}}

C

T1ρT \propto \frac{1}{\rho}

D

T1mT \propto \frac{1}{\sqrt{m}}

Step-by-Step Solution

  1. Identify the Restoring Force: When the block is depressed by a small distance xx, an additional volume of liquid V=AxV = Ax is displaced. According to Archimedes' Principle, this creates an additional upthrust (buoyant force) which acts as the restoring force. Frestoring=(Weight of displaced liquid)=(Axρ)gF_{restoring} = -(\text{Weight of displaced liquid}) = -(Ax\rho)g
  2. Determine Spring Constant (kk): Comparing this to the standard SHM equation F=kxF = -kx, we identify the effective force constant k=Aρgk = A\rho g.
  3. Apply Time Period Formula: The time period of a particle/body in SHM is given by T=2πmkT = 2\pi \sqrt{\frac{m}{k}} . Substituting k=Aρgk = A\rho g: T=2πmAρgT = 2\pi \sqrt{\frac{m}{A\rho g}}
  4. Analyze Proportionality: From the derived formula, the relationship between time period TT and cross-sectional area AA is: T1AT \propto \frac{1}{\sqrt{A}} (Note: It is also proportional to m\sqrt{m} and inversely proportional to ρ\sqrt{\rho}).

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from Oscillations. 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.

PHYSICSOscillationsrectangularcrosssectionfloatsliquiddensity

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