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A 3cm cube has its upper face displaced by 0.1cm by a tangential force.If modulus of rigidity of material is $5\times 10^4N/m^2$.Find the force

$\begin{array}{1 1}(A)\;3N\\(B)\;7.5N\\(C)\;4.5N\\(D)\;1.5N\end{array} $

1 Answer

$\Delta l=.1$cm,$l=3$cm
$a=l^2$=9$cm^2$
$\eta=5\times 10^4N/m^2$
As we know
$\eta=\large\frac{\text{Stress}}{\text{Strain}}$
$F=\eta(\large\frac{\Delta l}{l})$$a$
$\;\;\;=5\times 10^4\times \large\frac{.1}{3}$$\times 9\times 10^{-4}$
$\;\;\;=1.5N$
Hence (D) is the correct answer.
answered May 7, 2014 by sreemathi.v
 

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