(a) State the principle of conservation of momentum. (b) Ball A moves with speed v along a horizontal frictionless surface towards a stationary ball B, as shown in Fig. 3.1. [Figure 3.1] Ball A has mass 4.0 kg and ball B has mass 12 kg. The balls collide and then move apart as shown in Fig. 3.2. [Figure 3.2 (not to scale)] Ball A has velocity 6.0 m s⁻¹ at an angle of θ to the direction of its initial path. Ball B has velocity 3.5 m s⁻¹ at an angle of 30° to the direction of the initial path of ball A.