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A vessel contains oil (density = 0.8 gm/cm3) over mercury (density = 13.6 gm/cm3). A uniform sphere floats with half its volume immersed in mercury and the other half in oil. The density of the material of sphere in gm/cm3 is:

Option: 1

3.3


Option: 2

6.4


Option: 3

7.2


Option: 4

12.8


Answers (1)

best_answer

 

Net force on the body -

F_{B}+F_{v}= W

\rightarrow 6\pi \eta rv+\frac{4}{3}\pi r^{3}\sigma g= \frac{4}{3}\pi r^{3}\rho g

\rightarrow 6\pi \eta rv=\frac{4}{3}\pi r^{3} g\left ( \rho -\sigma \right )

\rightarrow v_{t}=\frac{2}{9}\frac{ r^{2} \left ( \rho -\sigma \right )}{\eta }g

 

- wherein

F_{B}-Buoyant \: force

F_{v}-viscous \: force

w-weight

\rho \rightarrow density \: of \: ball

\sigma \rightarrow density \: of \: water

V_{T} =terminal \: velocity

 

 Here viscous force is zero

Weight = Buoyant force

Vp_{m}g=\frac{V}{2}p_{Hg}g+\frac{V}{2}p_{oil}g

p_{m}g=\frac{p_{Hg}+p_{oil}}{2}=\frac{13.6+0.8}{2}=\frac{14.4}{2}=7.2

Posted by

himanshu.meshram

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