Back to 'Unit 7: Work and Energy'

Topic outline

  • 7.5: Rotational Kinetic Energy

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    Why do tornadoes spin so rapidly? The answer is that the air masses that produce tornadoes are themselves rotating, and when the radii of the air masses decrease, their rate of rotation increases. An ice skater increases their spin in an exactly analogous way. The skater starts their rotation with outstretched limbs and increases their spin by pulling them in toward their body. The same physics describes the spin of a skater and the wrenching force of a tornado. Clearly, force, energy, and power are associated with rotational motion.

    We cover these and other aspects of rotational motion in this unit. We will see that important aspects of rotational motion have already been defined for linear motion or have exact analogs in linear motion.

    We can write an equation for the rotational kinetic energy (the energy of rotational motion) as: KE_{\mathrm{rot}}=\frac{1}{2}I \omega^{2}