The game of billiards involves a total of 16 balls that can be solid or striped. The game is often played by two or four players with each of the players receiving long sticks. The clubs are used to hit all the balls in each of the pockets, on each side of the table. To win, the remaining players must hit all 8 balls in one of the pockets until the end of the game. But how is this game related to physics?
When we go out to play pool, many of us don’t realize how physics affects the game. If we stop and take the time to understand the basics of physics, it is amazing to see the degree to which we can improve our skills. The physics behind billiards (pool), in a larger image, involves collisions between two billiard balls. When two billiard balls collide, the collision is called elastic. The definition of elastic collision is “A collision in which colliding objects bounce off without lasting deformation or the generation of heat.” People can assume that for collisions involving billiard balls, the collision will be completely elastic.
For collisions involving the two billiard balls, momentum will always be conserved. The definition of moment is “The mass multiplied by its speed”. In a collision with another billiard ball, both balls exert a force on each other called momentum. This is similar to Newton’s Third Law of Physics, which says that “The forces that things exert on each other are always equal in force and opposite in direction.” This also means that the momentum is equal and opposite. The connection between momentum and momentum is that momentum equals the change in momentum of each ball. If the change is similar to each other, the change in total momentum must equal zero. If the change in total momentum is zero, then the total momentum must be the same before and after the collision. This concept is called conservation of momentum.
In one example, let’s say you’re trying to hit the 8 ball into the pocket in the corner. Once you hit the cue ball, your momentum will be mass times speed. The momentum of the 8 ball is zero because it is not moving yet. If you hit it directly and the cue ball stops before colliding, then all the cue ball momentum goes to all 8 balls, because momentum is conserved. If you hit it at an angle, both billiard balls will keep moving after the collision. If you add the momentum of the balls, it will equal the momentum of the cue ball before the collision occurs. The 8 ball travels at an angle opposite to the direction you hit it, so you can always direct where you want the ball to go, if you hit it at the right angle.
Understanding how conservation of momentum and collisions works will likely help your game of billiards to some extent. But there are some complications that we have not mentioned. When playing pool, you should be aware that the balls may be sliding, rolling, or spinning. Also, you need to worry about friction and unevenness on the surface of the pool table. In the end, if you sit down and try to calculate what would happen when you hit the cue ball, you will find yourself in a tough spot.