Whn sand is poured on a rotatory disc what happens to its angular velocity. Explain

Answer 1

If the disk is free to move, then pouring sand on it slows it down. Angular momentum is conserved
AngMomDisk+angmomeumfallingSand=angular momentum disk/sand

Since final angular momentum is constant, and consists of the mass of sand on the disk, and the angular velocity, increasing the mass has to decrease anglar velocity.