Angular Momentum of Colliding Pucks: 80g & 120g Mass, 4cm & 6cm Radius

[vijay123]

dear ppl,
a puck of mass 80g and radius 4cm slides along an air table at a speed of 1.5m/s. it makes a glancing collision with a second puck of radius 6cm and mass 120g. because their rims are coated with glue, the stick together and spin after the collison. find their angular velocity.

the ans is 9 rad/s but i keep getting 19 rad/s. my doubt is that does the puck that slides carry any angular momentum by itself? i think it doesn't have coz its sliding but i am not sure...thanks

 

[Doc Al]

While the sliding puck has zero angular momentum about its center of mass, it certainly has angular momentum about the center of mass of the two puck system. (And it's the angular momentum of the system that remains the same.) Hint: What's the velocity of the center of mass?