13 The diagram below shows the initial state of two identical balls A and B before collision and the
final state immediately after the collision.
The mass of each ball is 1.2 kg.

Before the collision, the velocity of A is 3.0 ms and B is stationary.
A makes an oblique collision with B.
After the collision, A moves off at an angle of 30° to its original direction and has a velocityof 2.6 m s. B is deflected at an angle with a velocity of 1.5 m s.
a Explain why the final momentum of the system in a direction at right angles to the initial
velocity of A is zero. Hence determine the angle 0.
b Show that the total momentum of the system is conserved.