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Physics · SYSTEMS OF PARTICLES AND ROTATIONAL MOTION
हिन्दीA flywheel has moment of inertia \( I = 0.8 \text{ kg m}^2 \). A steady torque accelerates it from an initial angular speed of \( 10 \text{ rad s}^{-1} \) to \( 30 \text{ rad s}^{-1} \) in \( 4 \text{ s} \). The instantaneous power delivered by the torque at \( t = 2 \text{ s} \) is:
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Correct answer · Option C
\( 80 \text{ W} \)
Explanation
\( \alpha = \frac{30 - 10}{4} = 5 \text{ rad s}^{-2} \). Torque \( \tau = I\alpha = 0.8 \times 5 = 4.0 \text{ N m} \). At \( t = 2 \text{ s} \), \( \omega = 10 + 5(2) = 20 \text{ rad s}^{-1} \). Instantaneous power \( P = \tau \omega = 4.0 \times 20 = 80 \text{ W} \).
