Answer, and give a reason. A solid sphere and a hollow sphere have the same mass and radius…

Step 1. (a) The hollow sphere ($\tfrac23 MR^2$ against $\tfrac25 MR^2$): all its mass is at the outside.

Step 2. (b) Putting the mass at the rim gives the largest $I$ for that mass, so the flywheel stores more energy, $\tfrac12 I\omega^2$, and resists changes in speed better.

Step 3. (c) The pole raises the walker's moment of inertia about the rope. A wobble then turns her more slowly, giving her time to correct it.