Q.4(a) AB and AC are similar uniform rods, of length a, smoothly joined at A. BD is a weightless bar, of length b, smoothly joined at B, and fastened at D to a smooth ring sliding on AC. The system is hung on a small smooth pin at A. show that the rod AC makes with the vertical an angle b tan-1. a+va-b2 9 (b) Two uniform solid spheres composed of the same material and whose diameters are 6 in. and 12 in. respectively, are firmly united. Find the centre of mass of the combined body.