Conservation laws are very helpful tools in understanding how the world works. In this exhibit conservation of energy and conservation of momentum are both involved. When something is conserved, it means that the overall value does not change over time.

Energy is a measure of the ability to do work and can change between different forms such as kinetic, thermal, chemical, nuclear, acoustic, radiant and gravitational. The overall energy is precisely conserved. Momentum is a measure of mass in motion and has a direction. Unlike energy, momentum does not have other forms. The overall momentum is precisely conserved.

This exhibit is similar to a pendulum except that there is a collision in the middle of the swing. It is made from hardened steel balls which have very elastic collisions. This means that the kinetic energy (or energy of motion) of the outgoing balls is only slightly less than that of the incoming balls. A small amount is converted to heat (or thermal energy). The balls also have momentum and this is transferred from the incoming to the outgoing balls. These two conservation laws impose somewhat different restrictions on the possible outcomes of the collision and are the main reason for the behavior observed, namely that the outgoing balls match the incoming balls in number and velocity.

Energy is one of the main reasons we need to eat food. Food contains chemical energy that our bodies can convert to thermal energy to keep warm and also to kinetic energy to move about and do work. Energy is why it's harder to bike uphill. Going uphill increases your gravitational energy and your body must supply this energy by doing work. Energy is why power plants require an energy source. Some inventors have wasted years of their lives trying to invent "perpetual motion machines" that could produce work without any energy source. They have all failed since such a machine would violate conservation of energy.

Momentum is the reason it's important to wear a seatbelt in the car. If a car stops suddenly, a passenger's momentum can be safely reduced by a sustained force from the seatbelt. Momentum is why a hammer can drive a nail into a piece of wood. When the hammer hits the nail, the hammer's momentum is reduced to zero by a very intense force over a very short time during which it drives the nail further into the wood. In a head on collision between two cars, the combined momentum may actually be zero because they are moving in opposite directions and the individual momentums cancel each other out. Thus after the collision, both cars are at rest. In a rocket ship, any increase in forward momentum must equal the backward momentum of the rocket exhaust. If the fuel runs out, the ship can neither speed up nor slow down.

Sir Isaac Newton was born in the year 1642, the same year that Galileo died. He discovered the laws of motion that determine the behavior of this exhibit and many other things. He discovered the law of gravitation which indicates that gravity exists not just between you and the earth but between all objects including between the earth and the sun. Combining gravity with the laws of motion he was able to explain why the earth revolves around the sun and why the moon revolves around the earth. Newton was one of the most important scientists of all time. Newton's laws of motion apply to many engineering problems. They apply to anything that has moving parts (including fluids). They can explain sound waves through air and the vibrations of a guitar string. Newton and Leibniz are both credited with discovering calculus, a very important mathematical tool used in most branches of science and engineering. Newton also discovered that white light from the sun is made up of all the colors of the rainbow mixed together. He did not however invent Newton's cradle. Simon Prebble, an English actor, came up with it in 1967.