Question

A ring of radius 0.5 m and mass 10 kg is rotating about its diameter with an angular velocity of 20 rad/s. Its kinetic energy is

• A. 10 J
• B. 100 J
• C. 500 J
• D. 250 J

Answer 1

Answer: (D)

250 J

Answer 2

Rotational kinetic energy $\frac{1}{2}I\omega^{2} = \frac{1}{2}\left( \frac{1}{2}MR^{2} \right)\omega^{2}$

$= \frac{1}{2}\left( \frac{1}{2} \times 10 \times (0.5)^{2} \right)(20)^{2} = 250J$