Here is a problem 0% of my students got. It is not nearly as subtle as the
worm, but some of you might enjoy it. It is not original, but I don't
recall where I found it, so if someone recognizes it, let us know where it
came from.
Chip
An ice-skater is travelling at 11 m/s when she grabs a 32 meter rope attached
to a fixed vertical pole with a radius of 0.20 m. At the instant she grabs the
rope it is stretched out from the pole, perpendicular to her path.
After she grabs the rope, her path is constrained by the length of the
rope, and she spirals inward toward the pole as the rope winds around it.
At the moment that the free end of the rope is 16 meters long, what is
the speed of the skater?
Is the skater's kinetic energy conserved? Why or why not?
Is the skater's angular momentum conserved? Why or why not?