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QJEEM22Phcbd6: JEE Main 2022 Physics - Class 11 JEEM22Phcbd6 Solution: The distance of centre of mass from end A of a one dimensional…

The distance of centre of mass from end A of a one dimensional rod (AB) having mass density ρ=ρ0(1−x2L2)kg/m\rho=\rho_{0}\left(1-\frac{x^{2}}{L^{2}}\right) \mathrm{kg} / \mathrm{m} and length L (in meter) is 3Lαm\frac{3 L}{\alpha} \mathrm{m} . The value of α\alpha is ___________. (where x is the distance from end A)

Step-by-Step Verified Solution

ρ=ρ0(1−x2L2)\rho = {\rho _0}\left( {1 - {{{x^2}} \over {{L^2}}}} \right) kg/m

xcm=A∫0Lρ0(1−x2L2)x dxA∫0Lρ0(1−x2L2) dx{x_{cm}} = {{A\int\limits_0^L {{\rho _0}\left( {1 - {{{x^2}} \over {{L^2}}}} \right)x\,dx} } \over {A\int\limits_0^L {{\rho _0}\left( {1 - {{{x^2}} \over {{L^2}}}} \right)\,dx} }}

xcm=L22−L24L−L3=L242L3=3L8{x_{cm}} = {{{{{L^2}} \over 2} - {{{L^2}} \over 4}} \over {L - {L \over 3}}} = {{{{{L^2}} \over 4}} \over {{{2L} \over 3}}} = {{3L} \over 8}

⇒α=8\Rightarrow \alpha = 8

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