JEE Advanced 2013Paper 1
- Exam
- JEE Advanced
- Year
- 2013
- Paper
- Paper 1
- Subject
- Physics
- Chapter
- Mechanical Properties of Fluids
JEE Advanced 2013 · Paper 1 · Physics · Mechanical Properties of Fluids
A solid sphere of radius R and density ρ is attached to one end...
A solid sphere of radius R and density ρ is attached to one end of a mass-less spring of force constant k. The other end of the spring is connected to another solid sphere of radius R and density 3 ρ The complete arrangement is placed in a liquid of density 2ρ and is allowed to reach equilibrium. The correct statement(s) is (are)

Options
- AThe net elongation of the spring is \dfrac{4 π {R }^{3} ρ \text{g}}{3 k}
- BThe net elongation of the spring is \dfrac{8 π {R }^{3} ρ \text{g}}{3 k}
- CThe light sphere is partially submerged
- DThe light sphere is completely submerged
Correct answer
A. The net elongation of the spring is \dfrac{4 π {R }^{3} ρ \text{g}}{3 k}
Step-by-step solution
From equilibrium of sphere. \left(3 ρ\right)\text{kx} + 2 ρ \text{vg} - 3 ρ \text{vg}\text{kx} = ρ \text{vg}\text{x} = \dfrac{ρ \text{vg}}{\text{k}} = ρ \text{g} \dfrac{4}{3} \pi {\text{R}}^{3} \dfrac{ρ \text{vg}}{\text{k}} = \dfrac{ρ \text{g} \dfrac{4}{3} \pi {\text{R}}^{3}}{\text{K}}{\text{v}_{1} =\text{kx} + \text{mg} = {\text{F}}_{\text{B}}ρ \text{vg} + ρ \text{vg} = \text{2} ρ {\text{v}_{1} \text{g}= 2 ρ \text{vg} = 2 ρ {\text{v}_{1} \text{g}⇒ {\text{v}_{1} = \text{v}