Homework #11
Due in class Friday December 7th.
- One from Seth. A frisbee is thrown into the air with a definite wobble.
If air friction exerts a frictional torque -cω on the rotation of the frisbee,
show that the component of ω in the direction of the symmetry axis decreases
exponentially in time. Show also that the angle between the symmetry axis
and the angular velocity vector ω decreases in time if the moment of inertia
around the symmetry axis is larger than the other moment of inertia. (A
frisbee is a symmetric top.) Thus, the amount of wobble steadily diminishes
if there is air friction. Demo?
- 11-15) A classic piece of apparatus.
- 11-20) How fast is the tip of the rod going as it hits the ground? Compare
this with
the speed of a mass dripped from the same height.
- 11-25) What would this look like as it rolls?
- 11-29) How fast must a top spin to stay upright?
- 12-1) Drill.
- 12-7) A simple moment of inertia.
