Question

A wire is elongated by $2$ mm when a brick is suspended from it. When the brick is immersed in water, the wire constracts by $0.6$ mm. What is the density of brick?

• A. $3333kg/m^3$
• B. $4210kg/m^3$
• C. $5000kg/m^3$
• D. $2000kg/m^3$

Answer 1

The correct option is A $3333kg/m^3$

$\text{We know}$

$y=\frac{fL}{A\Delta L}\Rightarrow \frac{f}{\Delta L}=\frac{yA}{L}=k$

$f=k\Delta L$

So

fnet $={\rho }_B{V}_g-{\rho }_{\omega }vg$

${\Delta }_1\frac{K\times 2}{K\times 1\cdot 4}=\frac{{\rho }_{B}Vg}{({\rho }_B-{\rho }_{\omega })v_g}$

$\frac{10}{7}=\frac{{\rho }_B}{{\rho }_B-1000}$

$3{\rho }_B=10000$

${\rho }_B=3333{kgm}^{-3}$

Ans: $\left(A\right)$