si un disco que gira a 800 rpm se acopla a uno cuyo momento de inercia es del triple, ¿que rapidez angular tendra la combinacion?

the final angular velocity of the system would be 400 rpm

Explanation:

Recall that the kinetic energy of a rotating object is defined as:

where I is the object's moment of inertia, and its angular velocity.

If the kinetic energy is conserved in the coupling of the two discs, then the final kinetic energy of the new system should be the same:

therefore the new angular velocity will be:

half of the initial angular velocity. That is :

the final angular velocity of the system would be 400 rpm