Precession, Falling Cats, and The Intermediate Axis (of evil?) No matter how hard you try to teach your cat general relativity, you're going to fail. Brian Greene Physicist (String Theory), Columbia University

HINT: When solving problems involving both rotation (with torques) and translation (with forces), choose the + direction for rotation to be consistent with your + direction for translation. (In other words, a positive velocity v should be accompanied by a positive angular velocity omega.) This is more important than choosing a positive rotation to be "counterclockwise", which is just a convention, like putting +x to the right. In some problems (specifically involving yoyos) you can't satisfy both conventions and be consistent.

If the blob hits the door at an angle of 45°, as shown, the final angular velocity will be: A] twice as big B] √2 times larger C] the same D] √2 times smaller E] half as big

If the blob hits the door in the middle, as shown, the final angular velocity will be: A] twice as big B] √2 times larger C] the same D] √2 times smaller E] half as big

Falling Cats: Angular Momentum Not Needed to Rotate!

Rotation about any axis of symmetry requires no torque. However, rotation about the intermediate axis is unstable! If subatomic elementary particles are your bag: All have ‘spin’ (angular momentum) that can’t be stopped! No one knows why they have it. So far as any experiment has shown, they have zero size! (L=I  and I ≈ mr 2 and r=0 and L≠0. Go figure!)