1. Things are not what they appear to be: nor are they otherwise. - Buddha

2. If I apply a force that exerts a counterclockwise (+) torque on my yoyo, it will rotate: A] counterclockwise B] clockwise

3. If I exert a rightward force on my “semi” yoyo, it will move: A] to the right B] to the left

4. Does static friction do work on a rolling object? Short answer: NO. Long answer: both forces and torques do work. If the static friction force does + work (increasing K t ) Then the static friction torque does - work (decreasing K r ) (example: uphill rolling) These works exactly cancel: the effect of static friction is simply to move energy between rotation and translation. Bottom line: ignore work done by static friction!

5. When is  Unlike F=ma,  can only safely be used in two cases: I.Rotation about a fixed, predetermined axis II.Rotation about the center of mass (symmetric body) Always use a fixed axis, or the center of mass, for  ! If you are curious and would like to see how you can get a wrong answer using  come see me at an SI session.

6. The real deal: angular momentum