Final answer:
In a game of pool, when one ball hits another and causes it to move, it's an example of an elastic collision, where energy and momentum are largely conserved.
Step-by-step explanation:
In a game of pool, when one ball hits another and sets it into motion, this is an example of an elastic collision. Elastic collisions are events where the objects collide and bounce off each other without losing kinetic energy in the process. This phenomenon is common in a game of pool, where the balls scatter after the impact, largely conserving their momentum and energy, assuming there's no significant spin altering the outcome.
The other options provided do not accurately describe what happens when one pool ball hits another. Gravity, friction, and static electricity are forces that could influence a game of pool, but they are not primarily responsible for the motion of a pool ball after it is struck by another.