Conservation of Momentum
Momentum is the amount of matter that makes up an object, or mass, multiplied by the speed and direction of its movement, or velocity. In a closed system such as the swinging balls, the momentum of the first ball swung, prior to the collision, should equal the momentum of the ball that is pushed upward at the end of the series if left undisturbed. Momentum is expressed by a "P" in scientific notation while mass and velocity are notated with "m" and "v." Thus P = mv, and the initial P should equal the final P through conservation of momentum.
Conservation of Energy
Similar to conservation of momentum, conservation of energy states that the initial energy of the system must equal the system's final energy although the energy can and does switch from potential to kinetic and back again. As the balls swing, some of the energy is delivered to the air surrounding the system, thus causing the balls to gradually lose momentum.
Potential and Kinetic Energy
Potential energy is the energy stored within an object while kinetic energy is the energy of the object's motion. Potential energy, as a rule, is changed to kinetic energy. However, when the impact of the ball or balls that are falling occurs, a shock wave is sent through the stable balls, thus storing the kinetic energy as potential energy. As more collisions occur, the kinetic energy is dissipated.
Friction and Gravity
Other factors that play a part in the physics of swinging balls are friction and gravity. The friction in this system is found within the balls and is caused by the stored kinetic energy that was delivered through the shockwave. The gravity is actually an external force that is part of the system due to the suspension of the balls from the frame. As gravity and friction play their part in the system, the momentum decreases until the balls finally stop moving all together.