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A thin uniform copper rod of length l and cross-section area A and mass m rotates uniformly with an angular velocity `omega` in a horizontal plane about a vertical axis passing through one of its ends. The elongation of the rod will beA. `(momega^(2)l^(2))/(6AY)`B. `(momega^(2)l^(2))/(3AY)`C. `(momega^(2)l^(2))/(AY)`D. `(momega^(2)l^(2))/(2AY)` |
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Answer» Correct Answer - C Free expansion of rod = `alphaLDeltatheta=15 xx 10^(-6)xx2(50-20)=15xx10^(-6)xx2xx30=0.9mm` If expansion is fully prevented Strain = `(DeltaL)/(L)=(9xx10^(-4))/(2)=4.5 xx10^(-4)` Thermal stress = (strain)Y = `(4.5 xx 10^(-4))(2xx10^(11))=9xx10^(7)N//m^(2)` |
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