Aparticular uniform solid disk is rotating freely, and without any friction, about an axle passing through the center of the disk. the axis of rotation is perpendicular to the plane of the disk, as you might expect. from just above the surface of the disk, at one particular spot some distance from the center, sand is then dropped (from rest) carefully onto the disk, until a ring of sand has formed. while the sand is being added, the disk gradually slows down.

1. during this process, is angular momentum conserved?
a) yes, the angular momentum of the sand-disk system after the sand has been added is equal to the angular momentum the disk had originally.
b) no - the sand/disk system has less angular momentum afterwards than the disk had originally.
c) no - the sand/disk system has more angular momentum afterwards than the disk had originally.

2. during this process, is kinetic energy conserved?
a) yes, the rotational kinetic energy of the sand-disk system after the sand has been added is equal to the rotational kinetic energy the disk had originally.
b) no - the sand/disk system has less rotational kinetic energy afterwards than the disk had originally.
c) no - the sand/disk system has more rotational kinetic energy afterwards than the disk had originally.