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Et represents total mechanical energy, expressed in Joules.

This activity enables us to approach the concept of Gravitational Potential Energy (PE).

In our illustration, the original Potential Energy is arbitrarily chosen to be at the lowest point. (PE = 0 when h = 0). Potential Energy, expressed in Joules, is proportional to the mass (expressed in kilograms) and the altitude (expressed in meters) according to the equation:

PE = mgh

Only mechanical energy is represented. If one realizes  that Et is conserved, this is because the Potential Energy is transformed into Kinetic Energy (not shown in the animation) according to the unalterable relatioinship: Et = KE + PE.

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