6.System of Particles and Rotational Motion
medium

$10\ kg$ દળ અને $0.5\ m$ ત્રિજયા ધરાવતો પદાર્થ $2\ m/s$ ના વેગથી ગતિ કરે છે.તેની કુલ ગતિઉર્જા $32.8\ J$ હોય,તો ચક્રાવર્તન ત્રિજયા .......... $m$ શોધો

A

$0.25$

B

$0.2$

C

$0.5$

D

$  0.4$

Solution

Given total $\mathrm{KE}(\mathrm{E})=32.8 \mathrm{J},$ mass $(\mathrm{m})=10 \mathrm{kg}$

velocity $(v)=2 m / s .$ Radius $(r)=0.5 \mathrm{m}$

NOW

Total $\mathrm{KE}(\mathrm{E})=\mathrm{E}_{\text {transalational }}+\mathrm{E}_{\text {rotational }}$

$\Rightarrow E=\frac{1}{2} m v^{2}+\frac{1}{2} I \omega^{2}$

$\Rightarrow \mathrm{E}=\frac{1}{2} m v^{2}+\frac{1}{2} m k^{2}\left(\frac{v}{r}\right)^{2},$ where $\mathrm{k}=$ radius of gyration

$\Rightarrow 32.8=\frac{1}{2} \times 10 \times 2^{2}+\frac{1}{2} \times 10 \times k^{2}\left(\frac{2}{0.5}\right)^{2}$

$\Rightarrow 32.8=20+80 \times k^{2}$

$\Rightarrow k^{2}=\frac{12.8}{80}=0.16$

$\Rightarrow k=0.4 m$

Standard 11
Physics

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