1. The problem statement, all variables and given/known data Actually, my confusion originated from solving two different problems... 1) A point object of mass 'm' moving horizontally hits the lower end of the uniform thin rod of length 'l' and mass 'm' and sticks to it. The rod is resting on a horizontal, frictionless surface and pivoted at the other end as shown in figure. Find out just after collision the angular velocity of the system. 2) A circular wooden loop of mass 'm' and radius 'R' rests flat on a horizontal frictionless surface. A bullet, also of mass 'm', and moving with a velocity 'V', strikes the loop tangentially and gets embedded in it. The thickness of the loop is much less than 'R'. The angular velocity with which the system rotates after the bullet strikes the loop is ... 2. Relevant equations mrCMvCM +ICM ω2 = constant 3. The attempt at a solution I solved both questions using the above formula exactly in the same way, but was able to solve only (1).... What I am confused with is that whether to add the external particle moment of inertia in "ICMω2" I applied the formula independently for both objects, that means the particle's MoI about its own CM is 0. I get the answer in (2) if I add Consider the MoI of the ring to be 2mR2 instead of simply mR2... If I follow this approach in (1), then I get another answer which is not correct.... What to do?? Any help would be greatly appreciated.