This would be an example of deposition (Phase transition).
Explanation:
Given that,
Initial speed of the billiard ball 1, u = 30i cm/s
Initial speed of another billiard ball 2, u' = 40j cm/s
After the collision,
Final speed of first ball, v = 50 cm/s
Final speed of second ball, v' = 0 (as it stops)
Let us consider that both balls have same mass i.e. m
Initial kinetic energy of the system is :

Final kinetic energy of the system is :

The change in kinetic energy of the system is equal to the difference of final and initial kinetic energy as :
So, the change in kinetic energy of the system as a result of the collision is equal to 0.
Boyle's law states:
pV = C, where p = pressure, V = volume, C = constant.
Therefore,
p1V1 = p2V2
And the,
p2 = p1V1/V2
p1 = 512 kPa
V1 = 5l
p2 =?
V2 = 4l
Therefore,
p2= 512*5/4 = 640 kPa
I believe the answer is electric