The left end of a rod of length and rotational inertia is attached to a frictionless horizontal surface by a frictionless pivot,
as shown above. Point C marks the center (midpoint) of the rod. The rod is initially motionless but is free to rotate around the pivot. A student will slide a disk of mass toward the rod with velocity 0 perpendicular to the rod, and the disk will stick to the rod a distance x from the pivot. The student wants the rod-disk system to end up with as much angular speed as possible