Conservation of Energy

There are plenty of examples of the conservation of energy.  This post will simply look at the changes of gravitational potential energy and kinetic energy.

Within a closed system the amount of energy remains constant and energy is neither created nor destroyed. Energy can be converted from one form to another (potential energy can be converted to kinetic energy) but the total energy within the system remains fixed.

Let's use the example above.  The ball on a frictionless pendulum will swing forever.  However, the energy is converted repeatedly as the ball swings back and forth.  At the highest point of the swing, it stops moving for an instant. Kinetic energy is therefore zero, and because its at its highest point, the potential energy is greatest.  At the bottom of the swing when the pendulum can go no lower, the kinetic energy is greatest and the potential energy is at its lowest.  Therefore we can see that the energy has been converted.

An example that we studied in the lab was the falling object through the light gates at certain heights.  Some groups found that nearly all of the calculated gravitational potential energy had been converted to kinetic energy which was measured and calculated.

A great example of conversions of energy is a hydro electric dam.  Here we have potential energy being stored behind the wall of the dam, which is converted to kinetic energy when travelling down the penstock and the turbine and then electrical energy at the generator.