This lab involves "angular collisions" of the two disks on the same air pressure rig used in the torque and angular momentum lab.� Students will relate angular momentum before the collision to angular momentum after the collision.� They are also asked to relate kinetic energy before and after the collisions.� They will make use of the equation for the moment of inertia of a uniform disk rotating through its center I=½mr2, the angular momentum L=Iω, and rotational kinetic energy K=½Iω2.� They may need to be reminded that angular momentum can be positive or negative depending on the direction of rotation.�