Conservation of angular momentum: (angular momentum L = I w) In a system of two colliding objects R and D, the total angular momentum before collision = the total angular momentum of the system after collision (providing there are no external torques like frictional of Conservation of Angular torques acting in the system). This is a statement of the Momentum. In equation form: IR WR + ID WD IR WR' + ID (D' IR 27tfr + ID 2nfD = (IR + ID) 2xtfRD ' (since @ = 2ntf) Therefore, IR fr + ID fo = (IR + ID) fRD ' ...... (1) (angular momentum before collision) (angular momentum after collision) 3 . A stationary 2 kg ring of radius 0.20 m is dropped from rest on to a freely rotating 10 kg disc of radius 0.20 m rotating at 16 Hz (see picture below). Stationary ring Spinning disc (a) Draw labelling lines to the disc and the ring. [2] (b ) Calculate the moment of inertia of the ring (Iring = MR2) [2] (c) Calculate the moment of inertia of the disc (Idisc = = MR2). [2] (d) State the initial rotational frequency, fr , of the ring in Hz. [1] (e) State the initial rotational frequency, fo, of the spinning disc in Hz. [1] (f) Assuming angular momentum is conserved, use equation (1) to determine the final rotational frequency, fRD' , of the ring and disc combination. [2]