Final answer:
In an elastic collision where a moving billiard ball hits a stationary one of the same mass, the stationary billiard ball will take on the velocity of the first, ending up with a velocity of 2.5 m/s after the collision.
Step-by-step explanation:
The subject of this question is Physics, specifically focusing on the topic of elastic collisions and the conservation of momentum. When a moving billiard ball collides elastically with another billiard ball of the same mass that is at rest, the conservation of momentum and energy principles can be applied. In an elastic collision between two objects of equal mass where one object is initially at rest, the moving object will come to rest after the collision, and the previously stationary object will move with the velocity that the first object had before the collision. Therefore, the second billiard ball will move with a velocity of 2.5 m/s after the collision, assuming no external forces and a perfectly elastic collision.