Unit 9: Angular Momentum
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 her spin in an exactly analogous way. The skater starts her rotation with outstretched limbs and increases her spin by pulling them in toward her 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. These and other aspects of rotational motion are covered in this unit. We will see that all important aspects of rotational motion either have already been defined for linear motion or have exact analogs in linear motion.
Completing this unit should take you approximately 16 hours.
9.1: Kinematics of Rotational Motion
Watch this lecture, pausing to take notes, before moving on to the reading below.
Read sections 10.1 and 10.2 of "Chapter 10: Rotational Motion and Angular Momentum" (pages 317 to 326). Look over the corresponding conceptual questions on page 348 to test your understanding of the sections.
Scroll down the page to "Ch 9: Rotational Motion," and select the link to open the PDF document. Read the entirety of Chapter 9. From pages 9-4 to 9-10, solve problems 1-4, 10-13, 16, and 21.
9.2: Dynamics of Rotational Motion
Read sections 10.3 and 10.4 of "Chapter 10: Rotational Motion and Angular Momentum" (pages 326 to 336). Look over the corresponding conceptual questions on page 349 to test your understanding of the sections.
Work on solving problems 3 from SAC103 and 1, 2, and 3 from SAC123. The solutions are available, but make a serious attempt to solve the problems before looking at the solutions.
9.3: Conservation of Angular Momentum
Read section 10.5 of "Chapter 10: Rotational Motion and Angular Momentum" (pages 336 to 341). Look over the corresponding conceptual questions on pages 349-351 to test your understanding of the sections.
Follow this animation through the various steps until you can convincingly explain what a cat does to land on its feet to a non-physics student.
Work on solving problems 1 through 4 from SAC105. The solutions are available, but make a serious attempt to solve the problems before looking at the solutions.