(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.

1. (a)State the principle of conservation of momentum.[2]
2. (b)(i)By considering the components of momentum at right-angles to the direction of the initial path of ball A, calculate θ.[3]
3. (b)(ii)Use your answer in (i) to show that the initial speed v of ball A is 12 m s⁻¹. Explain your working.[2]
4. (b)(iii)By calculation of kinetic energies, state and explain whether the collision is elastic or inelastic.[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.