Rotational Kinetic Energy: Practice Problem & Solution

Short Solution (Best for NEET):

To solve this problem, we apply the core principles of Rotational Kinetic Energy. Understanding the underlying formula is key to arriving at the correct answer below:

Under zero external torque, angular momentum is conserved: \( I_1 \omega_1 = I_2 \omega_2 \). If \( I_2 = I_1/4 \), then \( \omega_2 = 4\omega_1 \). The ratio of kinetic energy is \( \frac{K_2}{K_1} = \frac{\frac{1}{2}I_2\omega_2^2}{\frac{1}{2}I_1\omega_1^2} = \frac{1}{4} \times 16 = 4 \implies 4 : 1 \).