Physics · University
Rotational kinetic energy
Use moment of inertia about the stated rotation axis. Angular speed is in radians per second.
Method and conditions
Use moment of inertia about the stated rotation axis. Angular speed is in radians per second.
K = Iω²/2
Worked examples
A rigid body rotates about a fixed axis with moment of inertia 8.7 kg·m² and angular speed 28 rad/s. Calculate its rotational kinetic energy. Round the final result to 4 decimal places if needed. Answer in J.
K = (8.7)(28)²/2.
3410.4 J
A rigid body rotates about a fixed axis with moment of inertia 3.9 kg·m² and angular speed 15 rad/s. Calculate its rotational kinetic energy. Round the final result to 4 decimal places if needed. Answer in J.
K = (3.9)(15)²/2.
438.75 J
Try it
A rigid body rotates about a fixed axis with moment of inertia 3.3 kg·m² and angular speed 14 rad/s. Calculate its rotational kinetic energy. Round the final result to 4 decimal places if needed. Answer in J.
A rigid body rotates about a fixed axis with moment of inertia 7.3 kg·m² and angular speed 12 rad/s. Calculate its rotational kinetic energy. Round the final result to 4 decimal places if needed. Answer in J.
Check your work
Answers and marking notes
- 323.4 J
K = (3.3)(14)²/2.
- 525.6 J
K = (7.3)(12)²/2.
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