# Physics of Pinball

Pinball is a fast pace game of physics and skill. With the knowledge of the mechanics and the physics of how the game works it can be played more effectively. Friction, gravity, potential energy, kinetic energy, circuits and momentum are just a few of the aspects of physics apply.
The first thing to do to start a game of pinball is to insert the coin. This alone requires many fundamental aspects of physics. The player inserts the coin and lets gravity take over. Gravity accelerates the coin to a certain speed in a specific direction or what is called velocity. The coin, which has mass, is now moving at a certain velocity. The coin now has linear momentum. To find the momentum of the coin we would take the mass and multiply it by the velocity. If the velocity were doubled (the coin doubles in speed) then the momentum of the coin would double. The coin then strikes a lever transferring some of its momentum to the lever. The coin then drops into the coin box. Usually this lever is a small wire similar to a paper clip. It has to be of small mass or the momentum of the coin would have lesser of an effect. When the coin strikes the lever it transfers some of its momentum and causes the lever to move. The lever is connected to a switch. This switch momentarily completes a circuit causing electrons to move through the system to notify the game system to start and release a ball into the ball shooter. Amazingly this all happens in the space of about a second.
Once the ball is in the ball shooter the player pulls on the plunger to compress the spring. This is called work. The player applies force to the plunger and pulls it a certain distance. In this case it?s only a couple of inches. The physics definition of work is force multiplied by distance (Kirkpatrick and Wheeler p136). If the distance is doubled the amount of work is doubled. The player has now compressed the spring in the ball shooter. The ball sitting in the ball shooter is at rest. It will be at rest until acted on by an unbalanced force. This is Newton?s first law of motion, the law of inertia (Kirkpatrick and Wheeler p31). The ball shooter is then released the spring decompresses and strikes the ball sending it up the incline to the top of the pinball playing field. The strike on the ball is called the impulse. The time interval it takes for the ball momentum to change. Since the ball has no momentum because it has zero velocity the ball shooter transfers its momentum at the impulse (The Ball Shooter 2003). This also takes place in the time frame of about a second.

The ball now has kinetic energy. Kinetic energy like momentum in that it comes from the mass of the object and its velocity. Kinetic energy was transferred from the plunger to the ball just like momentum was but only if the collision was elastic. During and elastic collision kinetic energy is conserved. The balls kinetic energy is half of its momentum squared. This means the balls momentum is its mass multiplied by velocity, and then it is squared and divided by two. If the velocity or speed of the ball is reduced by one half then the overall kinetic energy is reduced by a factor of four (Kirkpatrick and Wheeler p.106)

The ball uses this kinetic energy to move up the usually 6 to 7 degree incline to the top of the playing field. The kinetic energy of the ball is now converted to
gravitational potential energy. The gravitational Potential energy is calculated by multiplying the mass by the force of gravity and the height of the ball?s position (Kirkpatrick and Wheeler p139). The gravitational force on the ball through the entire game will always be 9.8 m/s squared. The force of gravity is not necessary for game of pinball but it is necessary for it to play properly. Without gravity it would more likely play like a game of bumper pool. The player would have to aim his shots to bounce at angles and try to get the ball back to the flippers.

With gravity intact the ball?s tendency is to have its gravitational potential energy convert back to kinetic energy and roll down the incline. With many obstacles in its way the ball eventually will reach the bottom of the playing field. Unless the flippers strike the ball to continue the game, the ball will go down the drain.

One aspect of physics that went unmentioned above was friction. Friction is force acting against the ball moving against the surface. Friction was disregarded for two reasons. First it is involved in almost very aspect listed above and second the game could be played in a frictionless environment if one existed. The lack of friction would most likely not affect the game in most ways. The only noticeable difference is the ball would move faster.

The game requires a lot of strategy. Getting the ball to move in the direction the player wants is difficult. Most players? strategy consists of just keeping the ball from going in the drain. Some players try to apply force to the side of the machine. This is called a tilt. The object is to adjust the incline of the playing field to move the ball into a more desirable position. Tempting as this may be there is a mechanism in the machine that will punish the player if he or she tries to tilt.

The tilt mechanism is a simple machine that consists of a metal conducting ring and a metal pendulum. This illustrated below.

By applying force to the machine to cause it to shake or move will cause the pendulum to swing. The pendulum is at rest until force moves it. If the pendulum is moved to far the metal rod or shaft of the pendulum will make contact with the conductive ring and cause a circuit to complete and signal the machine to shut the flippers off. This will cause the ball to roll down the incline and down the drain (Brannon 2003).

Understanding how physics is used in an every day pinball machine will help with the strategy of the game. Knowing how the tilt works and how much force to apply when shooting the ball can improve any ones? game. Even in an environment without friction or gravity pinball can be played. Without physics the game would not exist. Nor would anything exist.

Physics of Pinball 9.4 of 10 on the basis of 1866 Review.