Question

A disc of moment of inertia $'I_1'$ is rotating in horizontal plane about an axis passing through a centre and perpendicular to its plane w ith constant angular speed $?\omega_1'$. Another disc of moment of inertia $?I_2?$ having zero angular speed is placed coaxially on a rotating disc. Now both the. discs are rotating with constant angular speed $?\Omega_2 ?$. The energy lost by the initial rotating disc is

• A. $\frac{1}{2} \left[ \frac{I_1 + I_2}{I_1 I_2 } \right] \omega_1^2$
• B. $\frac{1}{2} \left[ \frac{I_1 I_2 }{I_1 - I_2} \right] \omega_1^2$
• C. $\frac{1}{2} \left[ \frac{I_1 - I_2}{I_1 I_2 } \right] \omega_1^2$
• D. $\frac{1}{2} \left[ \frac{I_1 I_2 }{I_1 + I_2} \right] \omega_1^2$

Answer 1

Answer: (D)

$\frac{1}{2} \left[ \frac{I_1 I_2 }{I_1 + I_2} \right] \omega_1^2$

Answer 2

Answer (d) $\frac{1}{2} \left[ \frac{I_1 I_2 }{I_1 + I_2} \right] \omega_1^2$