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A fly wheel rotating about a fixed axis has a kinetic energy of 360 joule when its angular speed is 30 radian/sec. The moment of inertia of the wheel about the axis of rotation is

1. 0.6 kg·m²
2. 0.15 kg·m²
3. 0.8 kg·m²
4. 0.75 kg·m²

Correct answer: 0.15 kg·m²

Solution

The rotational kinetic energy is given by \( KE = \frac{1}{2} I \omega^2 \). Substituting \( KE = 360 \) J and \( \omega = 30 \) rad/s, we solve for \( I \): \( I = \frac{2 \times 360}{30^2} = 0.8 \) kg·m².

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