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Through friction (like when you are driving and you get off the gas, friction, and a little gravity, causes you to slow down and not keep going forever).

Through heat. Like an incandescent light bulb that use more energy for heat and less for light, which is one reason the other light bulbs are more efficient. Your not paying to heat your home with a light bulb.)

Potential energy can be lost by a change in altitude.

Friction and heat are good

Light production can also be a sign of losing energy. Think of a burner on the stove glowing.

Radioactive decay.

Production of sound. Two objects striking one another sends out a sound shockwave of energy.