Qualitatively describing the energy changes taking place during one cycle of an oscillation

• Consider the pendulum to the right which is placed in position and held there.
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• Let the green rectangle represent the potential energy of the system.
• Let the red rectangle represent the kinetic energy of the system.
• Because there is no motion yet, there is no kinetic energy. But if we release it, the kinetic energy will grow as the potential energy diminishes.
• A continuous exchange between E_K and E_P occurs.

Consider the mass-spring system shown here. The mass is pulled to the right and held in place.

• Let the green rectangle represent the potential energy of the system.
• Let the red rectangle represent the kinetic energy of the system.
• A continuous exchange between E_K and E_P occurs.
• Note that the sum of E_K and E_P is constant.
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• FYI ∙If friction and drag are both zero E_T = CONST.
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• If we plot both kinetic energy and potential energy vs. time for either system we would get the following graph